V S M Q A O

PALAEONTOGRAPHICAC-BEITRAGE ZUR N A T U R G E S C H I C H T E DER VORZEIT

ABTEILUNG BPALXOPHYTOLOGIE

HERAUSGEGEBEN VON

H.-J. SCHWEITZERIN BONN

B A N D 210

LIEFERUNG 1—3

UNTER MITARBE1T VON

R. BELOW, BONN; M. N. BOSE, LUCKNOW; M. BOULTER, LONDON; W. L. FRIEDRICH, AARHUS; J. GAL- TIER, MONTPELLIER; L. MATTEN, CARBONDALE; W. RIEGEL, GOTTINGEN; D. VOGELLEHNER, FREIBURG BR.

INHALT:

HLUST1K, ANTONIN:PSEUDOFRENELOPSIS PARCERAMOSA (F o n t a in e ) W a tso n FROM THE LOWER CRETACEOUS OF MORAVIA, CZECHOSLOVAKIA. (PAGE 1 -8 . WITH 3 FIGURES IN THE TEXT.)

LISTER, J. K. and BATTEN, D. J.:STRATIGRAPHIC AND PALAEOENVI RON MENTAL DISTRIBUTION OF EARLY CRETACEOUS DINOFLAGELLATE CYSTS IN THE HURLANDS FARM BOREHOLE, WEST SUSSEX, ENGLAND. (PAGE 9—89. WITH 13 PLATES, 16 FIGURES AND 2 TABLES IN THE TEXT.)

S T U T T G A R TE. S C H W E I Z E R B A R T ’ S C H E V E R L A G S B U C H H A N D L U N G

( N A G E L E u. O B E R M I L L E R )1988

Palaeontographic4 Abr. B 210 Lfg. 1-3 9-89 Stuttgart, September 1988

STRATIGRAPHIC AND PALAEO- ENVTRONMENTAL DISTRIBUTION OF EARLY CRETACEOUS DINOFLAGELLATE CYSTS IN

THE HURLANDS FARM BOREHOLE, WEST SUSSEX, ENGLAND

BY

J. K. LISTER and D. J. BATTEN, Aberdeen >

With 13 plates, 16 figures and 2 tables in the text

Summary

The taxonomy, stratigraphic ranges and distribution of dinoflagellate cysts and other algae, and associated acritarchs from the Weald Clay (uppermost Barremian) and Lower Greensand (lower to upper Aptian) are documented from a borehole section in southern England. Among the 140 formally, and 15 informally described cyst taxa are two new species, Australispbaern pscudovitrea and Taleispbaera? uipi/Iju. The diagnosis of Achomosphaera verdiiri is also emended. On the basis of the data accumulated it has been possible to erect 7 informal dinocyst zones encompassing 17 key palynomorph horizons- These form a basis for correlation with the Isle of Wight and other Lower Cretaceous sequences in southern England.

The Weald Clay is the product o f a long period of deposition in part o f a shallow, fresh to variably saline basin. Sediments that accumulated when salinity levels were low commonly contain the non-marine dinocysts Hurlandsia rugarnm and Aumahsphaera fragtiis. Raised salinities are indicated by the presence of many specimens of a small number of marine and marginal marine species, viz, Subliliiphana perlucida, Pseudoceralium ptllifnum, Aus/ralispbaera pteudotutrta, Cydonepbdium vannopborum sensu DuXBURY 1983 and Takisphaeraf capillata. The assemblages from the Atherfteld Clay Formation are dominated by peridiniacean and ceratiacean forms, but there is an abundance of miospores and much fragmentary detritus derived from land plants in association. The entire palynofacies reflects deposition in a near-shore environment in which the salinity of the transgressive Lower Greensand sea was probably a little below normal. In the overlying Hythe and Bargate Beds an increase in the number of gonyaulacacean cysts and peaks in the diversity of the whole assemblage, accompanied by a decline in both the abundance and variety of miospores, are associated with transgressive and regressive phases in a more offshore, open marine environment.

The Portsdown Swell, which separated the Weald and Wessex Sub-basins of the Wessex-Weald Basin, is envisaged to have been locally emergent and vegetated while the Atherfteld Clay was deposited but progressively inundated during subsequent deposition of the Hythe Beds. Boreal and Tethyan influences on the dinocyst assemblages are implied by certain cyst associations. Although some of the Weald and Atherfteld Clay palynofacies point to restricted conditions of deposition, this rarely led to the accumulation of large quantities o f amorphous organic matter. As a result, little or no source potential for hydrocarbons is indicated at any level in the succession.

Contents

I. Introduction .............................................................................................................................. 10II. Geological background ............................................................................................................ 10

III. The Hurlands Farm Borehole sequence................................................................................... 14IV. Methods .................................................................................................................................... 16

) Address of the authors: Mrs. I. K. Lister and Dr. D. J- Batten, University of Aberdeen, Department of Geology and Mineralogy, Marischal College, Aberdeen, AB9 IAS, Great Britain.

Palaconcogrdphica. Abe. B. Bd. 210 20375-0299/88/0210-0009 $ 42.30

© l°88 E. Sthweirerbart’sche Verlagsbuchhjndlung, D-7000 Stuttgjn I

V. Systematic palynology ............................................................................................................. 16VI. Stratigraphic distribution in Hurlands Harm Borehole sequence ........................................ 47

VII. Comparison ol Aptian assemblages with those ol similar age from elsewhere .............. 50VIII. Correlation of Hurlands Farm Borehole and Isle ol Wight sections................................. 57

IX. Provisional dinocyst zonation for the latest Barremian to late Aptian of southern England 57X. Palynofacies and palaeocnvironmcnts ................................................................................... 63

XI. Wider implications of palaeoenvironmcntal interpretations ............................................... 76XII. Conclusions .............................................................................................................................. 78

XIII. Acknowledgments...................................................................................................................... 78XIV. References .................................................................................................................................. 78XV. Explanation of plates................................................................................................................ 84

I. IntroductionThis paper is based on a palynological investigation of 37 productive core samples from the British Geological

Survey (BGS) borehole at Hurlands Farm, near Selham, West Sussex in the southwest Weald (National Grid Reterence SU9413 2104; Text-fig. 1). Seven of these represent the uppermost Weald Clay of the Wealden Group and the other 30 are from the Atherfield Clay, Hythe Beds and part of the Bargate Beds of the Lower Greensand Group. The objectives are to 1) describe the non-marine and marine dinocysts encountered, 2) establish a biostratigraphy for the borehole section based on these palynomorphs, 3) compare the cyst assemblages with those described from elsewhere, 4) correlate the borehole sequence with sections on the Isle of Wight, 5) erect a provisional dinocyst zonation for the upper Barremian to upper Aptian of southern England which is linked to the standard ammonite zonation, and 6) consider the palaeoenvironmental implications of the distribution of the dinoevsts in conjunction with the miospores and palynofacies.

II. Geological backgroundThe Wealden District occupies a large tract of land in southern England, encompassing the major part of the

county of Kent, the whole of Sussex, the southern half of Surrey and a small part of Hampshire (Casey 1961, G allois 1965; Text-fig. 1). It is up to 217 km from east to west and 80 km from north to south, its topographic- boundaries being the North and South Downs which are prominent hills of Upper Cretaceous chalk. Geologically, the Wealden part of the Wessex-Weald Basin extends across the Straits of Dover into the Bas Boulonnais of northern France.

There have been four stages in the structural development of the region since the Early Carboniferous: 1) A late Palaeozoic period of tectonism culminating in a platform of f olded rocks. The main fold trends are east southeast and attributable to the Hercynian orogeny (Variscan Front). 2) Downwarping and sedimentation during the Mesozoic. Subsidence of the folded Palaeozoic rocks began in the Triassic and continued throughout the Jurassic and Early Cretaceous. This was accompanied by sporadic uplift along the margins, particularly during the deposition of the Lower Greensand. 3) A late Early to Late Cretaceous phase when differential subsidence effectively ceased and the Lower Greensand was successively overlain during a major transgression by Gault Clay, Upper Greensand and the Chalk. 4) Uplift and folding associated with the Alpine orogeny which raised the area not only above sea-level but also into a broad anticline, subsequent erosion of which has led to the present-day outcrop distribution of Lower Cretaceous strata.

The Wealden Beds comprise a thick series of fluvial, lacustrine and lagoonal fresh to brackish water deposits. The upper, predominantly argillaceous, Weald Clay is slightly thicker (up to 450 m) than the underlying sandier Hastings Beds (c. 400 m) and is considered to span most, if not all, of the Hauterivian and Barremian Stages. Sedimentation was largely controlled by vertical movements of tectonically active horst blocks which bordered the basin. Uplift and a concomitant increase in precipitation and competence of the rivers generated the arenaceous braidplain deposits of the Hastings Beds. Downfaulting coupled with steady subsidence led to the accumulation of the more argillaceous facies of this group. The low relief of the London-Bclgium massif , which provided much of the sediment deposited in southeast England during Weald Clay times, may also have been brought about by geomorphic decay associated with climatic (weathering) factors (Ai.len 1976, 1981). The reduction in bedload and

Text-fig. 1. Maps showing the areal extent of the Weald Clay and Lower Greensand in southeast England, the position of the Hurlands Earn-. Borehole in the southwest of the region together with the local geology (adapted from Humphries 1964) and place names mentioned in tex- The poorly exposed Atherfield Clay, which occurs as a narrow band between the Hythe Beds and Weald Clay, is omitted from the tigu-e

competence resulted in the deposition of considerable quantities of mud and the widespread development ot mudplain facies in both Weald and Wessex Sub-basins. Short-lived sandy interruptions have been attributed to upward movements in the adjacent massifs (A llen 1976). The sediments accumulated in “pro-fan” brackish lakes and lagoons which spread over, coalesced and transgressed the sandy braidplains and meanderplains represented by the upper part of the Hastings Beds. Salinities varied from fresh to brackish to almost fully marine. These fluctuations were caused by periodic invasions of the sea, probably from the north (Text-fig. 2). Weak tidal conditions, possibly suggested by alternations of clay and silt laminae, may have been established at times but water depths are not considered to have exceeded 2-3 m (Allen 1981).

Along with sedimentological and tectonic factors there were almost certainly also climatic and seasonal controls on salinities. The latter would have been reduced when precipitation and run-off increased over a long period, and raised when rainfall and evaporation were low during dry periods. Since the amount of rainfall was at least partly a function of the relief of the surrounding massifs (A llen 1981, Sladen & Batten 1984), when this was low during the late Barremian the climate would probably have been relatively dry. As a result, run-off would not have been sufficient to reduce the effect of marine incursions. Unstable salinities are well attested by numerous variations in the faunal and palynofloral content of upper Weald Clay deposits in southeast England and ot the Vectis Formation on the Isle of Wight.

A marine transgression flooded the basin at the end of the Barremian with the result that the overlying Lower Greensand Group consists of a succession of mudstones, siltstones and sandstones which reflect deposition in

shallow marine coastal environments. It ranges from early Aptian to early Albian in age and in the southeast is divided into 4 major lithological units, the Atherfield Clay, Hythe Beds, Sandgate Beds and Folkestone Beds Formations. These correlate with the Atherfield Clay, Ferruginous Sands, Sandrock and Carstone on the Isle of Wight where the Lower Greensand reaches its maximum thickness of c. 244 m (Text-fig. 3). Casey (1961) generated a zonation based on the rich fauna of ammonites recovered from these rocks which is not only applicable further afield, particularly in northwest Europe, but also an improvement on methods of subdivision of Aptian and Albian strata that were introduced earlier by Jacob (1907), Spath (1923-1943) and others, and applied mainly to French and German strata. More recently the composition of the main lithological units of the Lower Greensand has been considered by a number of authors to reflect world-wide eustatic events, which in turn were connected with rates of seafloor spreading and plate tectonic movements (e. g., M organ 1980b, D ewey 1982).

The junction between the marine Atherfield Clay and the underlying Weald Clay is usually clearly delineated. The two units in most parts of the Wcssex-Weald Basin are usually separated by a disconformity, with only minor erosion and folding preceding the deposition of the Atherfield Clay, but in some places erosion may have been

B O R E A L S E A

C O R N U B I A

B O R E A L S E A

T E T H Y S

0 °

Text-fig. 2. Tentative regional palaeogcography during the A) late Barremian, B) early Aptian-fissicostatus Zone, C) late early Aptian- • -jerbanki Zone and D) late hy\\&x\-nutfielden$is Zone, based on M iddlemiss (1962b, figs. 1-3), Allen (1981, fig. 11). Where the Artois and Pomdown axes are labelled, it is assumed that they were at least partly emergent.

more severe (e. g., in parts of the western Weald; A llen 1976). The transgressive Pema Bed {fissicostatus Zone; Text- fig. 3) is not known in east Kent, suggesting that this area was not submerged until later.

The junction between the Atherfield Clay and the overlying Hythe Beds in the Wealden District is gradational, the top part of the former coarsening up into the glauconitic sands of Hythe Beds facies. This sandy influx is thought to have been generated by uplift of the adjacent London-Belgium landmass (G allois 1965, M jddlemiss 1975). The lithologies of the Hythe Beds are very variable. In the eastern part of the district they consist of alternating layers of bluish grey sandy limestone and grey calcareous, argillaceous sandstone speckled with glauconite. The sands, which are commonly cross-stratified, reflect clastic deposition in a shallow shelf sea under fairly strong tidal influence (N arayan 1963). The restricted distribution of the Hythe Beds in the eastern Weald, and in particular the variable development of the martinioides Zone and the partial to total removal of the desbayesi and bowerbanki Zones through erosion, suggest that sedimentary patterns were greatly affected by a combination of a period of regression and extensive tectonic movements on the southern fringes ot the London platform and elsewhere (C asey 1961, M iddlemiss 1967, M organ 1980b). Deposition of the Hythe Beds in the western Weald and of the Ferruginous Sands on the Isle of Wight was not greatly affected by these events; sedimentation continued with only minor interruptions. The absence of the Atherfield Clay and Hythe Beds on the Portsdown Swell (as recorded in the Portsdown borehole; Taitt & K ent 1958) between the Weald and Wessex Sub-basins may, however, be linked to them (K irkaldy 1937, p. 125).

The overlying Sandgate Beds (nutfieldensis Zone; nutfeldiensis in R aw son et al. 1978) are strongly transgressive. According to K irkaldy (1937) they overstep remnants of the Hythe Beds in East Sussex to rest directly on Weald Clay but this was not confirmed during mapping of the Brighton-Worthing Sheet (Institute of Geological Sciences (IGS) Ann. Rept. for 1975). They also extend onto the southern margins of the London platform and spread across Wiltshire into the Midlands (C asey 1961). The deposits are variable in composition and often difficult to

Text-fig. 3. Zonal classification and correlation of the Aptian part of the Lower Greensand succession on the Isle of Wight and in the western Weald, based on C asey (1961, Table 1), Rawson et al. (1978) and Simpson (1985).

AMMONITE ZONES ISLE OF WIGHT SUSSEX

z SANDROCK FOLKESTONE< HYPACANTHCPLtTES BEDS

JACOBIh-Cl san: ? i - e«£

PARAHOPLITESBEDS

i

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SANDS HYTHE

TROPAEUMB0WEPBANK1 BEDS

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FISSICOSTATUS

distinguish from the Hythe Beds. In the eastern Weald they consist of glauconitic sands with a basal phosphatic nodule bed containing fossils reworked from the martinioides and older zones.

Elsewhere, the lowest unit, known as the Bargate Beds (Text-fig. 3), typically consists of pebbly, calcareous sandstones, and in Surrey contains important developments of fuller’s earth. These montmorillonite-rich accumulations are thought to be volcanic ash which was deposited in a fluvial environment (M iddlemiss 1975, Young et al. 1978, A nderton et al. 1979, Sellw ood & Sladen 1981, Young & M organ 1981). The sites of igneous activity are unknown but they may have lain to the west or southwest of Britain and been linked with rifting associated with the opening of the Atlantic during the Early Cretaceous. On the northern margin of the basin in close proximity to the London platform the Bargate Beds appear, not surprisingly, to consist of littoral facies. These have been considered to reflect a minor regression associated with tectonic movements along the southern flanks of the platform prior to the main nutfieldensis Zone transgression (M iddlemiss 1962a, b).

III. The Hurlands Farm Borehole sequenceThe palynological sampling points are indicated on a diagram of the Hurlands Farm section (Text-fig. 4) which

is based on core descriptions by Young (1978) in the unpublished BGS record of the borehole. The following lithological descriptions are summarized from this report. We have accepted the stratigraphic subdivisions of the Weald and Atherfield Clays but, on the basis of the palynological evidence presented herein, interpret the “Lower Greensand undivided” to represent the Hythe and lower Bargate Beds. The Hythe and Sandgate (including Bargate) Beds cannot be separately distinguished in East Sussex (IGS Ann. Rept. for 1975, p. 21; Young & M organ 1981). However, recent mapping in West Sussex has indicated that the junction of these beds can be delineated there (Bristow 1983).

Weald Clay (104.68-98.28 m)The Weald Clay section consists mainly of silty, laminated, fissile mudstones which are generally medium to

dark greenish grey to olive black in colour. Pale grey silt wisps and very silty, lenticular beds up to 5 mm thick occur occasionally. Below 104.20 m the deposits are slightly calcareous and contain fish debris and ostracods. Above, they are generally characterized by being slightly bioturbated and containing minor channel features in silt laminae. Horizontal listric surfaces in the latter were recorded from 98.97-98.65 m. A nodular, granular band of pyrite up to 2 mm thick was reported at 100.44 and again at 98.65 m. A light brown ferruginous bed occurs between 101.54 and 101.52 m. Clearly defined surfaces with small silt-filled channels were recorded at 103.65 m, 103.52 m and 102.81 m and a sharp ?erosional base at 103.87 m. The main faunal horizons are between 102.38 and 101.55 m; these yielded comminuted fish remains, shell debris, small bivalves and pieces of large gastropods. Fish scales and other fragments were also recorded from 100.92-100.40 m, 100.34-100.18 m, 99.71-99.55 m and 98.65-98.28 m with scattered ostracods between 100.44-100.40 m.

A therfie ld Clay (98.28-85.24 m)A clearly defined bed of olive grey, bioturbated, muddy siltstone with a sharp base and oblique, silt-filled

burrows marks the Weald Clay-Atherfield Clay junction at 98.28-98.19 m. Above this horizon the sediments consist of mudstones that range in colour from olive grey-black to dark yellowish brown. They are slightly silty at first, becoming more so above 91.4 m. Traces of bedding and some distinct silt laminae were recorded from around 93.20 m and above. Clay ironstone septarian and other nodules frequently containing sphalerite (rarely pyrite and calcite) are relatively common above 97.75 m. Light brown ferruginous cement bands were recorded at 96.30- 96.16 m and 94.66 m. Occasional pyritised trails and horizontal burrows are present between 93.75-93.61 m and 88.39-87.55 m. The uppermost part of the Atherfield Clay (86.11-85.24 m) is moderately to strongly bioturbated. Shell fragments and bivalves are generally fairly common throughout the section with possible fish fragments being found at 96.94 m and 94.42 m, and a crushed echinoid or asteroid at 97.27 m.

H ythe beds (85.24->18.70 m)Part of the core (3.37 m from 84.33-80.96 m) was lost in loose sand towards the base of the Hythe Beds. The

beds comprising this section are mainly fine-grained, often hard sandstones which sometimes verge on sandy

■* 1 0 -0 -1 0 -5 m etres

-« 15 -0-15-5

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sandstone

siltstone

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lam ination poorly developed

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2 5

84- 3 - 8 5 085- 0 -8 5 -586- 0 -8 6 -587- 0 -8 7 -588- 0 -8 8 -589- 0 -8 9 -590- 0 -9 0 -5 9 1 0 -9 1 -5 9 2 0 -9 2 -5 9 3 0 -9 3 -5 9 4 0 -9 4 -5 9 5 0 - 9 5 - 5 9 6 0 - 9 6 -5 97-0 -9 7 -5 9 8 0 -9 8 -5 9 9 0 -9 9 -5

100-0-100-51010-101-51020-102-51 0 3 0-1035104-0-104-5104-5-104-68

Text-fig. 4. Hurlands Farm Borehole: formations, lithological sequence and sampling points; soil and river terrace deposits to 8.94 m

limestone. There are also a few olive grey, sandy or clayey, poorly laminated siltstones and olive grey silty, occasionally laminated mudstones. A number of sharp bases were logged along with three (at 62.69 m, 32.19 m and 25.99 m) that are also irregular. A thin band of fuller’s earth was recorded at 62.74-62.69 m. The beds become increasingly calcareous from 72.56 m upwards. They also contain a little scattered glauconite, which becomes more common above 71.73 m and is abundant at some horizons, giving the sediments a greenish colouration. Disseminated pyrite, frequently associated with burrows and trails, was occasionally encountered, more commonly between 72-57 m than elsewhere. Rare pyritised fossils, nodules and lignitic fragments were also observed

throughout the sequence along with phosphatic nodules, the latter being most common around 70-66 m. Many beds are moderately to strongly bioturbated. Oblique sub-horizontal and vertical infilled burrows are common, with horizons occasionally displaying more complex branching and anastomosing systems. “Chondrites- type” burrows were observed between 49.36-4934 m. The fauna includes ammonites, bivalves, rare gastropods, echinoids, asteroids, undifferentiated shelly debris, belemmtes (above 64.86 m) and scattered sponge spicules (more common above 60.68 m).

Bargate Beds (?18.70-10.00 m)The borehole was sited more or less on the boundary of the Hythe and Bargate Beds exposures. There is little

to distinguish the latter from the underlying Hythe Beds. Fine-grained, glauconitic, very calcareous sandstones which are also muddy, hard and strongly bioturbated, dominate the sequence. It is tempting to correlate a thin band (0.15 m) of fuller’s earth (69% montmorillonite) at 18.85-18.70 m with important seams of this material in the basal Bargate Beds of Surrey. Topley (1875) considered deposits of fuller’s earth near Petworth (c. 5.5 km from Selham; Text-fig. 1) to be more or less contemporaneous with those in the Sandgate Beds (see M iddlemiss 1975, p. 465). However, the presence of a martinioides Zone ammonite just above the Hurlands Farm fuller’s earth deposit may indicate that it is a little older than those in Surrey. The base of the Bargate Member may therefore be slightly diachronous. An alternative possibility is that the Hurlands Farm occurrence is at the top of the Hythe Beds, but the palynological evidence we present here indicates nutfieldensis Zone and hence Bargate Beds at least as low as 15.50 m.

IV. MethodsAll samples were prepared following the standard palynological techniques described in Batten & M orrison

(1983). The aim was to produce slide preparations that allow the total organic composition of the rock as well as the palynomorph content, unobscured by organic and inorganic debris, to be analysed. Five gm of each sample were placed in a polypropylene beaker and immersed in 20% hydrochloric acid (HC1) for a few hours. After washing several times, approximately 100 ml of 58-62% hydrofluoric acid (HF) were added and the samples left for at least 12 hours, occasionally being stirred during this period. The spent acid was then decanted and about 50 ml of concentrated HC1 and 100 ml of 58-62% HF added to the residues; the beakers were subsequently placed in a hot water bath for 3-4 hours to speed up the final stages of demineralization. After being neutralized by repeated addition and decantation of water the residues were transferred to a sintered glass funnel (porosity 2) fitted with an air-tight rubber bung to a Buchner filter flask with a hand bellows attached. Most were then immersed in 20% HC1 for several hours in order to clear any remaining mineral detritus and disaggregate lumps of colloidal material before some of the finely disseminated organic matter was removed by filtration. After further washing and prior to any more treatment, a kerogen slide of each preparation was made using glycerine jelly as a mounting medium. Brief oxidation by immersion in fuming nitric acid (HNOs) and agitation in an ultrasonic bath was carried out on the residues remaining when it was considered necessary to “clean” them by removing more finely disseminated organic matter. Two or three additional slide preparations were then made up, again using glycerine jelly. The margins of all cover-slips were enclosed by painting with Glyceel.

Routine traversing of the slides was undertaken at magnifications of x400 or x250 depending on the density of the palynomorphs and associated organic matter. The whole of the second slide from each preparation was examined in detail. Slides 1 (kerogen) and 3 were also scanned for photogenic specimens and for species not recorded in the initial logging. Two hundred microfossils were counted from each preparation in connection with the palynofacies analysis.

V. Systematic palynology1. Suprageneric classification of dinoflagellates

At present there is no generally accepted classification of dinoflagellates above generic level. Increasing knowledge of their life cycles has highlighted the inadequacies of systems with separate nomenclatures designed solely for the cyst stage of fossil dinoflagellates and for the cyst and thecate stages of living forms. The desirability

of recognizing the phylogenetic relationships between fossil genera and living dinoflagellate taxa within a comprehensive classification system has long been acknowledged but the attendant practical difficulties are not easily resolved- These are primarily connected with the complexity of cyst-theca relationships (Sarjeant & Downie 1966, 1974; Reid 1974, pp. 583-587; Evitt 1985, p. 275).

As a result, Sarjeant & D ow nie (1966, 1974) favoured an independent classification system for dinoflagellate cysts using form genera and “cyst-families” based purely on morphology, irrespective of whether the cysts were known to be directly related to modern motile taxa. Similar schemes which make more attempt to reflect phylogeny in the groupings were proposed by N orris (1978a, b) and Tappan (1980). However W all & D ale (1968, p. 291) argued that Sarjeant & D o w n ie’s classification was both non-biological and non-evolutionary. They advocated instead a unified system that would recognize biological and phylogenetic affinities within two natural lineage groupings, the Gonyaulacaceae and Peridiniaceae, fossil cyst taxa being defined and classified according to their morphological similarity to modern forms. Later W all & Evitt (1975) provided evidence for a third group, the Ceratiaceae. Lineage groupings also form the basis of a classification devised by W illiams (1977), and a simplified scheme of “G-cysts” and “K-cysts” (with variations) roughly corresponding to W all & D ale’s major lineage groups was used by Evitt (1985).

In view of the unsettled state of the suprageneric classification, some authors (e. g., D avey & Verdier 1971, D avey 1978, 1979a) have simply listed taxa alphabetically. Others (e. g.. Below 1981, 1982a, b; Brideaux & M cIntyre 1975; Brideaux 1977; D uxbury 1977, 1983) have adopted the flexible, informal classification procedures of W all & D ale which recognize phylogenetic trends within the major lineage groups without recourse to the complexities of formal nomenclature. In this paper the taxa are listed alphabetically within the Ceratiaceae. Gonyaulacaceae and Peridiniaceae and in an “unknown affinities” group.

2. Dinoflagellate cyst taxa encountered

All of the taxa recorded apart from those considered to be reworked are illustrated. Plate and figure numbers are indicated in the following list. The additional number in brackets refers to their position on Table 1. Species marked with an asterisk are discussed in section V. 4.

CeratiaceaeGenus: Aptea E isenack 1958 emend. D avey & Verdier 1974.

A. plera D uxbury 1983. Plate 1, figs. 2, 5. [97].*A. polymorpha E isenack 1958. Plate 1, figs. 3, 6, 9, 11. [116].A. securigera D avey & Verdier 1974. Plate 1, figs. 1, 4. [52].*A. sp. A. Plate 1, fig. 8. [138].

Genus: Australispbaera D avey 1978 emend. H arding 1986.*A. fragilis H arding 1986. Plate 3, figs. 1, 5. [2]."A. pseudovitrea Lister & Batten n. sp. Plate 3, figs. 2, 3. [23]. nA. vitrea Duxbury 1983. Plate 3, figs. 4, 9, 12, 13. [76].* A . sp. A. Plate 3, figs. 10, 14. [31-

Genus: Cerbia Below 1981.*C. tabulata (D avey & Verdier 1974) Below 1981. Plate 1, figs. 13, 14. [102].

Genus: Cyclonephelium D eflandre & C ookson 1955 emend. Stover & E vitt 1978.C. brevhpinatum (M illioud 1969) B elow 1981. Plate 2, fig. 8. [58],C. compactum D eflandre & C ookson 1955. Plate 1, fig. 7. [137].C. distinctum D eflandre & C ookson 1955. Plate 2, fig. 11. [48],C. bystrix (Eisenack 1958) D avey 1978. Plate 2, fig. 10. [59],C. inconspicuutn D uxbury 1983. Plate 2, fig. 7. [119].C. maugaad Below 1981. Plate 2, fig. 14. [49].

Palaeomographica. Abt. B. Bd. 210 3

C. palliatum (Brideaux 1977) Below 1981. Plate 2, fig. 15. [35],'C. vannopborum D aviy 1969 sensu Duxbury 1983. Plate 2, figs. 12, 13. [13].

Genus: Muderongia Cookson & Eisenack 1958.M. pariata D uxbury 1983. Plate 2, figs. 6, 9. [44].*M. sp. cf. M. simplex A lberti 1961. Plate 2, figs. 1, 5. [77],

Genus: Odontochitina D eflandre 1935 emend. D avey 1970.O. operculata (O. W etzel 1933a) D eflandre & Cookson 1955. Plate 2, fig. 3. [20].!'0. sp. aff. 0. striatoperforata C ookson & E isenack 1962. Plate 2, fig. 2. [51].

Genus: Pseudoceratium Gocht 1957.P. pelliferum Gocht 1957. Plate 2, fig. 4. [7],P. retusum Brideaux 1977. Plate 1, figs. 10, 12. [37].

GonyaulacaceaeGenus: *Acbomospbaera Evitt 1963.

"A. neptunii (Eisenack 1958) Davey & W illiams 1966a. Plate 11, figs. 10, 12, 13. [80]. *A. verdieri Below 1982a emend. Lister & Batten. Plate 11, figs. 6-9. [56].

Genus: Aldorfia Stover & E virr 1978.A. vectensis D uxbury 1983. Plate 5, figs. 18, 19. [139],

Genus: Apteodinium Eisenack 1958.*A. granulatum E isenack 1958. Plate 5, fig. 17. [109].*A. maculatum Eisenack & C ookson 1960. Plate 5, figs. 13, 14. [15].

Genus: Batiacaspbaera D rugg 1970.B. minor (Cookson & H ughes 1964) D orhofer & Davies 1980 subsp. psilata (Burger 1980) Lentin & W illiams 1985. Plate 5, fig. I. [110].*B. sp. A. Plate 5, figs. 5, 9. [112].

Genus: Callaiospbaeridium D avey & W illiams 1966b emend. D uxbury 1980.C. asymmetricum (Deflandre & Courteville 1939) Davey & W illiams 1966b. Plate 8, fig. 18. [72].C. trycherium D uxbury 1980. Plate 8, fig. 14. [87],

Genus: Cassiculospbaeridia D avey 1969.C. reticulata D avey 1969. Plate 5, figs. 6, 7. [9],

Genus: Cauca Davey & Verdier 1971.C. parva (Alberti 1961) Davey & Verdier 1971. Plate 10, fig. 2. [53].

Genus: Cblamydopborella C ookson & Eisenack 1958 emend. D uxbury 1983.*C. ttyei Cookson & Eisenack 1958. Plate 9, figs. 4, 5. [71|.C. trabeculosa (G ocht 1959) D avey 1978. Plate 9, figs. 2, 3. [10].*C. sp. A. Plate 9, figs. 6, 7. [114].*C. spp. [73].

Genus: Cleistospbaeridium D avey et al. 1966.C. huguoniotii (Valensi 1955) Davey 1969. Plate 9, figs. 8, 9. [57],

Genus:

Genus:

Genus:

Genus:

Genus:

Genus:

Genus:

Genus:

Genus:

Genus:

Genus:

*C. sp. A. Plate 9, fig. 13. [47],*C. sp. B. Plate 9, figs. 10, 11. (120].

Cometodinium D eflandre & Courteville 1939.C. wbitei (Deflandre & C ourteville 1939) Stover & Evitt 1978. Plate 9, fig. 12. [67],

*Coronifera Cookson & Eisenack 1958 emend. May 1980.!iC. oceanica Cookson & Eisenack 1958 emend. M ay 1980. Plate 11, figs. 2, 3. [39].*C. tubulosa Cookson & Eisenack 1974. Plate 11, fig. 4. [104].*C. sp. A. Plate 11, fig. 5. [132],

Cribroperidinium N eale & Sarjeant 1962 emend. H elenes 1984.C. conjunctum (Eisenack & C ookson 1960) Helenes 1984. Plate 6, figs. 1, 2, 5, 6. [121].C. diaphanc (Cookson & Eisenack 1958) Stover & Evitt 1978. Plate 6, fig. 3. [129].C. edwardsii (Cookson & E isenack 1958) Davey 1969. Plate 6, fig. 11. [94],*C. sp. cf. C. edwardsii (Cookson & Eisenack 1958) D avey 1969. Plate 6, figs. 7, 8. [82]. C. orthoceras (Eisenack 1958) Davey 1969. Plate 6, figs. 9, 10. [106],C. sepimentum N eale & Sarjeant 1962. Plate 6, fig. 4. [32]. r-C. spp. [5].

Ctenidodinium D eflandre 1938 emend. Woollam 1983.C. elegantulum M illioud 1969 emend. Below 1981. Plate 8, fig. 19. [33],

Discorsia D uxbury 1977.D. nanna (Davey 1974) Duxbury 1977. Plate 8, fig. 13. [40].

Dissiliodinium D rugg 1978.D. globulum Drugg 1978. Plate 4, figs. 15, 16. [81].

Ellipsoidiclyum Klement 1960.E. imperfectum (Brideaux & McIntyre 1975) Lentin & W illiams 1977. Plate 5, figs. 10, 11.

Endoscrinium (Klement 1960) Vozzhennikova 1967.£. bessebae Below 1981. Plate 8, figs. 6, 7. [88].E. campanula (Gocht 1959) Vozzhennikova 1967. Plate 8, figs. 2, 3. [130],E. glabrum (Duxbury 1977) Below 1981. Plate 8, fig. 4. [41],E. rostratum (Brideaux & McIntyre 1975) Below 1981. Plate 8, fig. 5. [140].

Exocbosphaeridium Davey et al. 1966.E. muelleri Yun 1981. Plate 10, figs. 20, 21. [68].E. pbragmites Davey et al. 1966. Plate 10, figs. 22, 23. [17],*£.? sp. A. Plate 10, figs. 15, 16. [30],

Florentinia D avey & Verdier 1973 emend. D uxbury 1980.F. cooksoniae (Singh 1971) D uxbury 1980. Plate 13, fig. 7. [42],F. interrupta Duxbury 1980. Plate 13, figs. 9, 10. [54],F. mantellii (Davey & W illiams 1966b) Davey & Verdier 1973. Plate 13, figs. 6, 8. [103].

Gonyaulacysta D eflandre 1964 emend. Sarjeant 1982.G. cretacea (Neale & Sarjeant 1962) Sarjeant 1969. Plate 7, fig. 9. [29].G. helicoidea (Eisenack & C ookson 1960) Sarjeant 1966b. Plate 7, fig. 8. [90].

[124],

*6.? kleithria Duxbury 1983. Plate 7, figs. 11-13. [83].* G. sp. cf. G. cassidala (Eisenach & C ookson 1960) Sarjeant 1966a. Plate 7, fig. 10. [135].

Genus: Heslerlonia Sarjeant 1966a emend. D uxbury 1980.H. heslertonensis (N eale & Sarjeant 1962) Sarjeant 1966a emend. D uxbury 1980. Plate 8, fig. 15. [6].

Genus: nHurlandsia L ister & Batten 1988.* H . rugarum (Piasecki 1984) Lister & Batten 1988. Plate 7, figs. 20-23. [1].

Genus: Hystrichodinium D eflandre 1935 emend. C larke & Verdier 1967.H. pulcbrum D eflandre 1935. Plate 10, fig. 1. [60],

Genus: Hystricbospbaeridium Deflandre 1937 emend. D avey & W illiams 1966b.H . recurvatum (White 1842) Davey & W illiams 1966b. Plate 12, fig. 11. [27],

Genus: Hystricbospbaerina Alberti 1961.H . scbindewolfii Alberti 1961. Plate 12, figs. 5, 8. [18].

Genus: Impagidinium Stover & Evitt 1978./. alectrolopbum (Sarjeant 1966a) Stover & Evitt 1978. Plate 7, fig. 14. [113].I. verrucosum (Brideaux & M cIntyre 1975) Stover & Evitt 1978. Plate 7, figs. 16, 17. [136].*/. sp. A. Plate 7, fig. 15. [36].

Genus: Kiokansium Stover & E vitt 1978 emend. D uxbury 1983.K. polypes (C ookson & E isenach 1962) Below 1982a. Plate 9, fig. 16. [19],

Genus: Kleitbriaspbaeridium D avey 1974.K . loffrense D avey & Verdier 1976. Plate 13, figs. 3, 4. [117],K. readei (Davey & W illiams 1966b) Davey & Verdier 1976. Plate 13, figs. 1, 5. [118],K. simplicispinum (Davey & W illiams 1966b) Davey 1974. Plate 13, fig. 2. [50],

Genus: Leberidocysta Stover & Evitt 1978.’'L.? eisenackii (M ehrotra & Sarjeant 1984a) L entin & W illiams 1985. Plate 8, figs. 12, 16, 17. [125],

Genus: Meiourogonyaulax Sarjeant 1966a.M . sagena (D uxbury 1980) Lentin & W illiams 1981. Plate 5, figs. 15, 16, 20. [92].M . stovcri Millioud 1969. Plate 5, figs. 8, 12. [89].

Genus: Microditiium C ookson & E isenach 1960a emend. Sarjeant 1966a.M . crinitum D avey 1969. Plate 5, figs. 3, 4. [108].M . opacum Brideaux 1971. Plate 5, fig. 2. [26],

Genus: Occisucysta G itmez 1970.0 . tentoria D uxbury 1977. Plate 7, figs. 6, 7. [78],0 . tenuiceras (E isenach 1958) Below 1981. Plate 7, figs. 4, 5. [122].

Genus: Oligosphaeridium D avey & W illiams 1966b emend. D avey 1982b.O. asterigerum (Gocht 1959) Davey & W illiams 1969. Plate 12, figs. 9, 10. [74],O. complex (White 1842) Davey & W illiams 1966b. Plate 12, fig. 6. [21].O. dividuum W illiams 1978. Plate 12, fig. 12. [66],

0. poculum J ain 1977. Plate 12, fig. 7. [25J.O. pulcherrimum (D eflandre & C ookson 1955) D avey & W illiams 1966b. Plate 12, figs. 13, 14. [11].

Genus: Operculodinium W all 1967.

Genus: Tanyosphaeridium D avey & W illiams 1966b.T. boletum D avey 1974. Plate 10, fig. 12. [45],T. regulare Davey & W illiams 1966b. Plate 10, fig. 11. [100],T. salpinx N orvick in Norvick & Burger 1976. Plate 10, figs. 14, 19. [34].T. variecalamus D avey & W illiams 1966b. Plate 10, fig. 13. [75].

Genus: Trichodinium E isenack & C ookson 1960 emend. C larke & Verdier 1967.T castanea (D eflandre 1935) C larke & Verdier 1967. Plate 6, fig. 14. [65].T. ciliatum (G ocht 1959) E isenack 1964. Plate 7, figs. 1-3. [105].

PeridiniaceaeGenus: Ascodinium C ookson & E isenack 1960a emend. H elenes 1983.

"’A. cinclum (Cookson & Eisenack 1958) H elenes 1983. Plate 4, fig. 10. [123].*A. diversum (Davey 1979a) H elenes 1983. Plate 4, figs. 4, 8. [133].A. incomptum (Duxbury 1983) Lentin & W illiams 1985. Plate 4, fig. 9. [131].*A. sp. A. Plate 4, figs. 3, 7. [96].

Genus: Batioladinium Brideaux 1975.B. jaegeri (A lberti 1961) Brideaux 1975. Plate 3, figs. 7, 8. [9].B. micTopodum (Eisenack & C ookson 1960) Brideaux 1975. Plate 3, fig. 6. [79],

Genus:11 Canningia C ookson & E isenack 1960b emend. Below 1981.*C.? turrita Brideaux 1977. Plate 3, figs. 11, 15. [22],

Genus: Cepadinium Duxbury 1983.~'C. variabile D uxbury 1983. Plate 3, figs. 16, 18-20. [8].

Genus: Dingodinium C ookson & E isenack 1958.*D. albertii Sarjeant 1966b. Plate 4, figs. 2, 6. [99].*D. cerviculum C ookson & Eisenack 1958. Plate 4, figs. 1, 5. [14],

Genus: Kalyptea Cookson & Eisenack 1960b.K. diceras C ookson & E isenack 1960b emend. Fisher & R iley 1980. Plate 4, fig. 17. [31]. K. monoceras C ookson & E isenack 1960b. Plate 4, figs. 13, 20. [85].

Genus: Palaeoperidinium D eflandre 1935 emend. Sarjeant 1967.P. cretaceum Pocock 1962 emend. D avey 1970. Plate 3, fig. 21. [12],

Genus: Pareodinia D eflandre 1947 emend. Stover & E vitt 1978.”P. ceratopbora D eflandre 1947 emend. Gocht 1970. Plate 4, fig. 14. [43].

Genus: Subtilispbaera J ain & M illepied 1973 emend. L entin & W illiams 1976.S. perlucida (A lberti 1959) Jain & M illepied 1973. Plate 3, fig. 17. [4].

Unknown affinities group

Genus: Caligodininm D rugg 1970.*C. sp. A. Plate 4, figs. 11, 12. [134],

11 The genus Canningia is not considered to belong to the peridiniacean group. It is included here because the paratabulation of C.? turrita indicates a peridiniacean affinity.

Genus: M aduradinium C ookson & E isenack 1970.*Af.> sp. A. Davey 1978. Plate 4, figs. 18, 19. [101].

Reworked jurassic taxa (alphabetical listing)

Chytroeisphaeridia cerastes Davey 1979b.Ctenidodinium spp.Glossodinium dimorphum Ioannides et al. 1977.Gonyaulacysta jurassica Deflandre 1938 emend. Sarjeant 1982. Scriniocassis dictyota (Cookson & Eisenack 1960b) Beju 1971. Scriniodinium inritibilum Riley in Fisher & Riley 1980.Systematophora orbi/era Klement 1960.Tubotuberclla apatela (Cookson & Eisenack 1960b) Ioannides et al. 1977.

3. Other palyoomorphs encountered

Forms considered to be acritarchs are listed alphabetically within the informal subgroups of D ownie et al. (1963). Green algae are omitted from these, being included instead within the Divisions Prasinophyta and Chlorophyta after Tappan (1980). Plate and figure numbers accompany all illustrated species. The number in parenthesis indicates the position of the taxon on Table 1 under the heading “Miscellanea”. Foraminiterai linings and scolecodonts are included in this group. The miospores have not been treated systematically because this paper is primarily concerned with the distribution of phytoplankton. The stratigraphic distribution of selected taxa have, however, been plotted on Table 2.

Acritarcha E vitt 1963

Acanthomorphitae:BalUsphaeridium cramer't Singh 1971. Plate 13, tig. 18. [14].Micrbystridium spp. Plate 13, figs. 16, 17. [9].

Polygonomorphitae:Veryhachium spp. Plate 13, fig. 14. [3|.

Sphaeromorphitae:Fromea amphora C ookson & Eisenack 1958. Plate 13, fig. 19 [10].F. complicata Brideaux 1977. Plate 13, fig. 13. [17].

Unclassified acritarchs:Eyrea nebulosa C ookson & Eisenack 1971. Plate 13, fig. 12. [5],Wallodinium krutzschii (A lberti 1961) H abib 1972. Plate 13, fig. 15. [15].W. tuna (Cookson & Eisenack 1960a) Lentin & W illiams 1973. Plate 13, fig. 11. [13],

Green Algae

Prasinophyta Round 1971Cymatiospbaera pachytheca Eisenack 1957. [8].Pterospermella aureolata C ookson & Eisenack 1958. [6],P. australiensis D eflandre & Cookson 1955. [7].P. eurypteris Cookson & Eisenack 1958. [4].Scbizosporis reticulatus C ookson & Dettmann 1959. [2],Tasmanites sp. [II].

Chlorophyta Pascher 1914 Botryococcus sp. [1|.

Other miscellaneousForaminiferal linings. [12]. Scolecodonts. [16].

4. Descriptions and discussion of selected dinocysts

A question mark immediately following a genus may indicate that either the assignment was considered tentative by the author of the species or it has been questioned by Lentin & W illiams (1985) or ourselves. A short, selected synonymy is included where this is considered relevant to the discussion of a taxon. The descriptive terms used are in general accordance with W illiams et al. (1978) and Evitt (1985). The Kofoidian system of paratabulation is followed. Size ranges given encompass the smallest, largest and the mean (in brackets) ot all observed values. A low number of measurements means that either few specimens were encountered or, because of poor preservation, accurate determinations were difficult to obtain. Occurrences mentioned refer only to the Hurlands Farm Borehole.

Division Pyrrhophyta Pascher 1914Class Dinophyceae Fritsch 1929Order Peridiniales Haeckel 1894Family Ceratiaceae Lindemann 1928

Genus: Aptea Eisenack 1958T ype s p e c ie s : A. polymorpha Eisenack 1958.

Aplea polymorpha E isenack 1958 Plate 1, figs. 3, 6, 9, 11

1958 A. polymorpha Eisenack, p. 399, pi. 22, figs. 5-12.1971 A. polymorpha - Singh, p. 370, pi. 63, figs. 5-7.1974 A. polymorpha - D avey & Verdier, p. 641, pi. 91, fig. 1.1980a A . polymorpha - M organ, p. 14, pi. 1, figs. 7-14.1983 A. polymorpha - Duxbury, pi. 1, figs. 4, 5.

H o lo ty p e : Eisenack 1958, pi. 22, fig. 5. M arne, north Germany; late Aptian.

D im ensions: Width, 69 (80) 90 pm; length without operculum, 62 (71) 80 pm; height of ornament, 3-15 pm (10 specimens).

Remarks: Specimens referred to A. polymorpha are similar to the German type material in exhibiting an ambitus of variable shape, ranging from typically asymmetrical to more rounded antapically, with an antapical horn present as a slight bulge. The ornament is more or less dense and usually non-tabular. It consists of broad, spinose elements 3-15 pm high which are commonly flared proximally and distally to form discontinuous, striated crests with serrated to furcate margins. Perforate crests arising from a similarly perforated periphragm have also been observed in a few individuals with particularly pronounced ornament. Partial intratabular grouping of elements (cf. Morgan 1980a, pi. 1, figs. 7-11) has been noted on a few specimens.

Forms that are morphologically intermediate between A. polymorpha and C. compactum have been encountered (see also Singh 1971, p. 370). These are characterized by having a more rounded antapex and a stronger ornament on the peripheral margins than A. polymorpha. Similar individuals showing a pronounced reduction in mid-ventral and/or mid-dorsal ornamentation have been referred to C. compactum; they are comparable with forms described by Duxbury (1983) as “C. compactum extreme”.

O ccurrence: Atherfield Clay, Hythe Beds, Bargate Beds.

Aplea sp. A Plate 1, fig. 8

D escrip tion : The two specimens identified as Aptea sp. A exhibit an apical archeopyle and an asymmetrical hypocyst with a distinct left antapical protuberance. The thin-walled, microperforate periphragm is closely adpressed to the endophragm. It is extended into numerous, generally thin processes 7-13 pm in length with bi- or trifurcate distal tips. Occasionally the processes are fused to form broader elements. They are penitabular in distribution and most are proximally connected by low ridges. An offset parasulcal notch was observed, accessory archeopyle sutures denoting the presence of 6 precingular paraplates.

D im ensions: Length without operculum, 56 pm; width, 70 pm (1 specimen).Rem arks: This species differs from A. polymorpha in lacking the development of crests.O ccurrence: Hythe Beds, Bargate Beds.

Genus: Australisphaera D avey 1978 emend. H arding 1986 Type species: A. verrucosa D avey 1978.

Australisphaera fragilis Harding 1986 Plate 3, figs. 1, 5; Text-fig. 5

1986 A. J'ragrfis Harding, p. 100, pi. 16, figs. 6-9; pi. 17, fig. 9; text-fig. 2.

H olotvpe: H arding 1986. pi. 16, fig. 6. Warlingham Borehole, Surrey; late Hauterivian.

D escrip tion : An extremely thin-walled, ceratioid cyst possibly consisting only of autophragm. Apical horn, when present, prominent, rounded and closed distally. Lateral horns developed as paracingular extensions, frequently with a pronounced distal notch. Antapical horns present as low protuberances of autophragm, sometimes quite prominent, left usually more strongly developed than right which may be absent altogether. Autophragm appears smooth or scabrate. A weakly delineated paracingulum is commonly visible. Archeopyle is apical, type (tA). Six precingular paraplates and an offset sulcal notch are indicated by accessory sutures.

D im ensions: Length with operculum, 67-77 pm; length without operculum, 48-55 pm; width, 50-58 pm (5 specimens).

Remarks: Numerous specimens oi Australisphaera, generally in a crumpled and torn state of preservation, have been referred to this taxon. They are invariably characterized by having an extremely thin, flimsy phragma. H arding (1986) suggested that the wall consists of two closely adpressed layers. This is not readily discernible in the specimens examined in the present study; his emendation of the genus is, therefore, only tentatively accepted. Similarly, the surface ornament of short echinae or granules he has described is not visible on our specimens but may be expressed by the faintly scabrate appearance of some.

A. pseudovitrea sp. nov. is similar in outline but has a variably developed surface granulation. A. vitrea D uxbury 1983 frequently exhibits a positive ornament, well developed, digitate lateral horns and a prominent antapical horn.

O ccurrence: Weald Clay.

Australisphaera pseudovitrea L ister & Batten n . sp.Plate 3, figs. 2, 3; Text-fig. 6

1983 A. vitrea Duxbury pars, p. 26, pi. 3, fig. 5, non pi. 2 fig. 11.

D erivation o f nam e: Gk. pseudos - false, with reference to the close relationship of this species to Australisphaera vitrea Duxbury1983.

H olotype: Plate 3, fig. 3. Sample 98.00-98.50 m, preparation MCP1602/2, England Finder reference U40/3, MPK 5428; Weald Clay - Atherfield Clay junction; latest Barremian.

Text-tig. 5. Camera lueida drawings o f specimens o f Australisphatra fragilis Harding 1986 illustrating the generally crumpled nature o f the flimsy phragma, apical archeopyle, pronounced lateral paracingular notches and variably developed antapical horns; c. X 1100.

D iagnosis: Proximate, thin-walled dinoflagellate cyst, ceratioid in outline, possessing one apical, two lateral and usually two antapical horns. Apical horn prominent, distaliy rounded, occasionally pointed and closed. Lateral horns developed as extensions of paracingulum which is distaliy notched, sometimes displaying rudimentary, slightly tapered projections below lateral post-paracingular margin. Right lateral horn more pronounced than that on left. Conical, left antapical horn usually more prominent than right, which may be very reduced or absent. Horns sometimes present simply as low bulges of autophragm.

Autophragm exhibits a sparse granular ornament which is particularly concentrated at distal extremities of horns and also partly defines paracingulum. Isolated short, rod-like processes and linear or vermiculate arrangements of similar, distaliy linked elements also observed on some specimens. Parasulcal area occasionally indicated by a ventral furrow lacking ornament. Archeopyle apical, type (tA) with a free operculum; margin slightly

to moderately zigzag, accessory sutures indicating presence of six precingular paraplates and a deep offset sulcal notch.

D im ensions: Length with operculum, 54 (80) 100 pm; length without operculum, 51 (55) 60 pm; width, 55 (67) 77 pm (20 specimens).

Remarks: This species differs from the holotype of A. vitrea D uxbury 1983 and similar forms in lacking pointed, well-developed digitate projections on the lateral horns and high, granular processes at the distal extremities of these and the other horns.

O ccurrence: Weald Clay - Atherfield Clay junction.

Australispbaera vitrea D uxbury 1983 Plate 3, tigs. 4, 9, 12, 13; Text-tig. 6

1983 A. vitrea Duxbury, p. 26, pi. 2, tig. 11, text-fig. 8.

H olotype: Duxbury 1983, p. 26, pi. 2, fig. 11, text-fig. 8. Lower Gryphaea Beds, Ferruginous Sands Formation, Atherfield section. Isle of Wight; early Aptian.

D im ensions: Length without operculum, 53 (65) 77 pm; width, 65 (81) 92 pm (5 specimens).Rem arks: D uxbury (1983) emended the diagnosis of Australispbaera to include forms exhibiting high

“spinose” ornament, this being specifically excluded originally (D avey 1978, p. 892). The holotype of A. vitrea is characterized by having coarse, granular fringes at the distal extremities of the horns (see D uxbury 1983, p. 27, text-fig. 8).

The specimens identified as A. vitrea during the course of this study differ from the holotype in lacking high spinose ornament, indeed sculpture is often minimal or absent altogether- When present, it consists of sparse granules concentrated at the distal extremities of the horns and along the paracingulum. Rare specimens exhibit isolated rods of granules 4-5 pm high on the lateral and antapical horns. On the other hand the vitreous autophragm, the digitate, post-paracingular projections and the prominent left antapical horn are characters which conform with the diagnosis of A. vitrea. Some degree of intraspecific variation exists in the variable length of the postcingular digitations exhibited by individual specimens.

D uxbury’s paratype of A. vitrea (1983, pi. 3, fig. 5) is considered to belong to a different species. It has been included here in A. pseudovitrea sp. nov. because its lateral horns lack sharply digitate projections.

O ccurrence: Atherfield Clay.

Australispbaera sp. A Plate 3, figs. 10, 14

D escrip tion : A species of Australispbaera consisting of a thin-walled autophragm devoid of ornament, with long (25-40 pm), digitate, postparacingular horns and a similarly long (c. 40 pm), left antapical horn. Archeopyle type (tA).

D im ensions: Length without operculum, 82-95 pm; width, 70-75 pm (2 specimens).Remarks: This rare form has been excluded from Australispbaera fragilis H arding 1986 because o f the

greater length of its horns.O ccurrence: Weald Clay.

Genus: Cerbia Below 1981Type species: C. labulata (Davey & Verdier 1974) Below 1981.

Cerbia labulata (D avey & Verdier 1974) Below 1981 Plate 1, figs. 13, 14

1974 Cyclnmphelium la bn/a Him D avey & Verdier, p. 630, pi. 92, figs. 1, 4; pi. 93, tig- 6.1981 Cerbia tabulata (Davey & Verdier 1974) Below, p. 9, pi. 4, figs. 3, 5; pi. 12, fig. 20, text-figs. 6a-c, g. 1983 Cerbia labulata - Duxbury, p. 29, pi. 1, figs. 6, 9, 12; text-figs. 11, 12.

Text-fig. 6. Camera lucida drawings comparing Auslralisphaeru vitrei Duxbcky (A) with Australispbaeru pseudovitrcn n. sp. (B); ornament excluded, c. X 750.

H olotype: Davey & Verdier 1974, pi. 92, figs. 1, 4. La Bedoule, southeast France; late Aptian (Gargasian).

Rem arks: The specimens of C. tabulata encountered exhibit either a rounded or an indented, bilobed antapex. Their shape does not appear to be governed by the overall size of the cyst. This is contrary to D uxbury’s (1983, p. 29) suggested correlation of an indented antapex with smaller individuals and a more rounded antapex with larger specimens. The cysts display a clear paratabulation, typically outlined by penitabular spines 2-12 pm high, which appears to agree with the formula proposed by D uxbury (1983, p. 30, text-fig. 11) of 6", 6c, 5", Is, lp

t t t

Following a re-examination of Eisenack’s (1958) type material of the German Aptian, Sarjeant (1985) considered Cyclonephelium bystrix (Eisenack 1958) Davey 1978 to be a senior synonym of Cerbia tabulata on the basis of a paratabulation pattern exhibited by the holotype of Tenua bystrix. He accordingly reinstated the genus Tenua Eisenack 1958, emended it to encompass paratabular features, and placed Cerbia in synonymy. Sarjeant's illustrations of the ventral view of the holotype of T. bystrix (op. cit., pi. 10, fig. 5) undoubtedly demonstrate a very weakly defined paratabulation but this feature was previously recognized by Evitt (1961) and also by Sarjeant & Stover (1978) when Tenua was originally placed in synonymy with Cyclonephelium. It is not unusual to encounter a suggestion of paratabulation, especially in the paracingular area, in species referred to Cyclonephelium, as noted by Below (1981, p. 8). In contrast, the delimitation of paratabular fields of Cerbia tabulata is very clear and this distinguishes it from the weakly paratabulate Cyclonephelium bystrix. Furthermore, Sarjeant still apparently considered T. bystrix to encompass forms similar to T. byslricclla (Eisenack 1958) which was placed by Brideaux & McIntyre (1975) in synonymy with T. bystrix. This form definitely exhibits a marginate distribution of processes (Sarjeant 1985, pi. 10, fig. 6).

In view of the confusion, we prefer to retain the concept of the genus Cerbia. Hence, Sarjeant’s proposal that Cerbia tabulata should be considered a junior synonym of Tenua bystrix is rejected.

O ccurrence: Atherfield Clay (isolated occurrences), Hythe Beds, Bargate Beds.

Genus: Cyclonephelium D eflandre & C ookson 1955 emend. Stover & E vitt 1978 Type s p e c ie s : C. compadum D eflandre 8c Cookson 1955.

Cyclonephelium vannophorum Davey 1969 sensu Duxbury 1983 Plate 2, figs. 12, 13

1983 C. vannophorum - D uxbury, pp. 34, 35, pi. 3, fig. 16.

H olotype: Davey, 1969, pi. 9, fig. 3, pi. 11, fig. 11. Compton Bay, Isle o f Wight; Cenomanian.

D escrip tion : Cyst subspherical in outline with a low apical prominence and a rounded to slightly bilobed antapex. Ornament composed of very fine, rod-like elements which bifurcate and are often medially or distally confluent, sometimes forming a distal reticulum. Processes 2-8 pm high, frequently longer at apex and antapex, concentrated on margins of cyst but commonly encroaching onto mid-dorsal area, being reduced or absent in sulcal zone. Paracingulum occasionally weakly defined by aligned processes. Periphragm scabrate to faintly reticulate in some specimens. Six precingular, accessory archeopyle sutures discernible. Archeopyle apical, type (tA); operculum free but often remaining attached.

D im ensions: Length with operculum, 74 (79) 82 pm; width, 60 (69) 75 pm (10 specimens).Remarks: Specimens attributed to this taxon are closely comparable to the form of C. vannophorum figured

by D uxbury (1983, pi. 3, fig. 16). They are distinguished from the species C. vannophorum sensu stricto (D avey 1969) because the fan-shaped processes that are characteristic of the Cenomanian type species are lacking in the Aptian forms.

In size, shape and distribution of processes C. vannophorum sensu D uxbury is similar to the Cenomanian C. cbabaca Below 1981. The latter differs, however, in having finer, longer processes which are distally linked by trabeculae to form a delicate reticulate network covering the entire cyst; the distal reticulum of C. vannophorum sensu D uxbury is only partially developed. Specimens of C. palliatum (Brideaux 1977) Below 1981 are generally

distinguished in having a rugulate to imperfectly reticulate periphragm supporting low, discrete, baculate to bifurcate processes which only rarely are longer and distally fused at the antapex, but there does appear to be some morphological merging with C. vannophorum sensu D uxbury.

O ccurrence: Weald Clay - Atherfield Clay junction.

Genus: Muderongia C ookson & Eisenack 1958Type s p e c ie s : M . ntcwbaa Cookson & Eisenack 1958.

Muderongia sp. cf. M. simplex Alberti 1961 Plate 2, figs. 1, 5

D escrip tion : A species of Muderongia with lateral horns which are either short, broad and distally notched or narrower, longer and distally truncated. Antapical horn short, broadly based and tapered to a pointed, or with a rounded, closed distal extremity. A second reduced antapical horn may be present as a low bulge. Pericoels are present around peripheral margins of endocyst which is smooth to finely granular. Paracingulum and paratabulation weakly defined on dorsal and ventral surfaces of endocyst. A parasulcal notch offset from midline also occasionally discernible. Archeopyle apical, operculum free.

D im ensions: Length without operculum, 72 (78) 87 pm; width, 80 (85) 89 pm (3 specimens).Remarks: This taxon differs from typical representatives of M. simplex in exhibiting a weakly defined

paratabulation and lacking a second, prominent antapical horn. It resembles the specimens figured by Alberti (1961, pi. 2, figs. 5, 6) which have a very reduced, second antapical horn. M. slaurota Sarjeant 1966b does not display any paratabulation and has tapering, pendant, lateral horns. M. pariata Duxbury 1983 also lacks paratabulation and in addition has a more symmetrical ambitus, distally perforate horns and an open antapical horn.

O ccurrence: Atherfield Clay.

Genus: Odontocbitina D eflandre 1935 emend. Davey 1970 T ype s p e c ie s : O. operailata (O. Wetzel 1933a) D eflandre & C ookson 1955.

Odontocbitina sp. aff. 0. striatoperforata C ookson & Eisenack 1962Plate 2, fig. 2

1971 0. itriatopcrforata - Singh, p. 372, pi. 64, figs. 3, 4; pi. 65, figs. 1, 2.1976 0. opirculaia-O. costuta Alberti 1961 group - Norvick & Burger, pp. 86-94, pi. 14, figs. 1-4.

Rem arks: A number of the specimens of Odontocbitina encountered are considered to be morphological intermediates of the O. operculata-O. costata (including O. striatoperforata) complex as discussed by N orvick & Burger (1976, pp. 89-94). They are distinguished from 0. operculata by the presence of short rows of minor perforations in a median position in one or more horns and are similar to the specimen identified as 0. striatoperforata by Singh (1971, pi. 64, figs. 3, 4). One individual in particular has quite extensive, well-developed, longitudinally aligned perforations up to 4 pm in length in its lateral and antapical horns. Rare specimens also show prominent antapical and apical protuberances of the endophragm identical to those figured in C ookson & E isenack’s 0. striatoperforata (1962, pi. 3, figs. 16, 19) and as illustrated by N orvick & Burger (1976, p. 91, fig. 18). Although no taxonomic significance was attached to this feature by N orvick & Burger, they only seem to occur on perforated cysts in our material.

These intermediate forms differ from 0. striatoperforata sensu stricto in lacking the striae or ribs typical of that species and in having smaller perforations located in a more or less median position on the horn rather than in a proximal to median position as on the type material. We agree with Singh (1971) in rejecting Clarke & Verdier’s (1967) synonymy of 0. striatoperforata with 0. costata because the latter species is strongly ribbed and either lacks, or displays only isolated perforations.

Our specimens occur somewhat lower in the stratigraphic record than those from Australia recorded by N o r v ic k & B u r g e r . Although these authors noted (p. 91) that forms with ‘rare, irregularly distributed, smoothsided holes’, which they interpreted as thin zones in the periphragm, do occur in the Aptian and Albian of the Great Artesian Basin, specimens with linearly arranged perforations similar to those found in the Atherfield Clay and Hythe Beds of the Hurlands Farm sequence do not seem to occur below the Albian (see N o r v ic k & B u r g e r op. cit., p. 94, figs. 16, 19).

O ccurrence: Atherfield Clay, Hythe Beds.

Genus: Pseudoceratium Gocht 1957T ype s p e c ie s : P peltiferum Gocht 1957.

Pseudoceratium pdliferum Gocht 1957 Plate 2, fig. 4

1957 P. petliferum Gocht, p. 166, pi 18, figs. 1, 2.

H o lo ty p e : G ocht 1957, pi. 18, tigs. la -c . Emsland, northwest Germany; Hauterivian.

D im ensions: Length without operculum, 82 (91) 100 pm, with operculum (1 specmen), 188 pm; overall width, 47 (52) 58 pm; length of lateral horn, 10 (22) 38 pm, antapical horn, 15 (33) 50 pm and apical horn, t>0-68 pm (11 specimens).

Remarks: The length of the horns of the specimens of P. pdliferum encountered in the Hurlands Farm succession varies considerably. The numerous specimens in one Weald Clay sample (101.00-101.50 m) have noticeably longer than average horns: antapical, 30-50 pm; lateral, 30-38 pm; apical, 60-68 pm. In other samples antapical and lateral horns range from 10-22 pm and 10-15 pm respectively. A probable ceratiacean paratabulation is discernible in some specimens but in most, only the paracingulum and a strongly zigzag archeopyle margin are visible.

O ccurrence: Weald Clay, Atherfield Clay, Hythe Beds.

Family Gonyaulacaceae L in d e m a n n 1928 Genus: Achomosphaera E v it t 1963

T ype s p e c ie s : A. ramulijha (Deflandre 1927) Evitt 1963.

Remarks: This genus was created by E v it t (1963) to include cysts with Hystricbospbaera (now Spiniferites)' type processes but which lack the parasutural ridges of that genus. Its validity has been questioned because weakly defined parasutural features occur on some specimens of species referred to it including the type, A. ramulijera. As a result it was considered to be a junior synonym of Spiniferites by Reid (1974), May (1980) and D uxbury (1983). Despite the problems, we consider, however, that Achomosphaera is sufficiently distinct from Spiniferites to justify its retention. We have reservations about placing the two genera in synonymy in view of the occasional presence of some intratabular processes in A. verdieri and the possibility of their presence in the holotype of A. neptunii, which would exclude these cysts from Spiniferites. The absence of the ‘well-developed parasutural ridges or septa’ (E v itt 1963) characteristic of Spiniferites is therefore considered to distinguish Achomosphaera from this genus.

Achomosphaera neptunii (E is e n a c k 1958) D a v e y & W il l ia m s 1966a Plate 11, figs. 10, 12, 13

1958 Baltisphaendium nepluni E isenack, p. 399, pi. 26. fig. 7, text-lig. 8.1966a Achomosphaera nepluni (E isenack 1958) Davey & W illiams, p. 51. pi. 3, fig. 7; pi. 9, fig. 11.1983 Spiniferites neptunii (Eisenack 1958) Duxbury, p. 55. pi. 7. figs. 13, 14.1985 Spiniferites cf. heterostyhs (Heisecke 1970) Stover & Evitt 1978; Sarjeant, pi. 10, figs. 3, 4.

H olotype: E isenack 1958, pi. 26, fig. 7. M arne, north Germany; late Aptian.

Remarks; A number of the specimens of A. neptunii encountered exhibit weak parasutural, crest-like features. These have also been noted by W illiams 8c D avey (1966a) and D uxbury (1983) in assemblages from the Speeton Clay of eastern England and the Lower Greensand of the Isle of Wight respectively, and by Sarjeant (1985) on Eisenack’s paratype of A. neptunii. The cyst appears to consist of two extremely thin, closely adpressed layers with the processes arising from the periphragm. A narrow cavation extends along parasutural boundaries, formed either by wrinkling or tension of the periphragm between the wide bases of the gonal processes. In specimens lacking parasutural features the periphragm and endophragm may well be so closely adpressed between the processes that they are completely fused. The form and inconsistency of this character supports the retention of the species in Achomosphaera rather than its inclusion in Spiniferites.

Sarjeant (1985) transferred the paratype of A. neptunii to Spiniferites cf. beterostylis (Heisecke 1970) Stover & Evitt 1978 and the holotype to Florentmia' neptunii, thereby concurring with Evitt (in Stover & Evitt 1978) that the processes of this specimen are intratabular. Evitt’s interpretation was, however, considered untenable by Duxbury (1980) on the grounds that bi- and trifurcate processes are typical of parasutural areas. Both for this reason and because no specimen was encountered in the Hurlands Farm sequence which supports his tentative interpretation of the holotype, Sarjeant’s treatment of A. neptunii is not accepted.

O ccurrence; Atherfield Clay, Hythe Beds.

Achomosphaera verdieri Below 1982a emend. Lister & BattenPlate 11, figs. 6-9

1974 A. cf. neptunii (Eisenack 1958) - Davey & Vesdier, p. 628, pi. 92, fig. 2.1979a A . cf. neptunii (Eisenack 1958) - Davey, pi. 1, figs. 2, 3.1982a A. verdieri Below, p. 3, pi. 8, figs. 10, 11; text-fig. 1.

H olotype: Below 1982a, pi. 8, fig. 11. "Profil E”, Morocco; Albiau.

Em ended diagnosis: A two-layered proximochorate to skolochorate dinoflagellate cyst, ovoidal to subspherical in shape, occasionally surmounted by a small apical boss. Periphragm finely granulate to microre- ticulate bearing numerous, smooth to slightly fibrous processes which are occasionally simple and acuminate but usually bifurcate or trifurcate and sometimes with a secondary bifurcation. Position of processes usually parasutural; rarely, intratabular processes also present. Archeopyle precingular, type P3".

D im ensions: Length 48 (51) 55 pm; width, 38 (42) 45 pm; length of processes 5 (12) 20 pm (6 specimens).Remarks: The diagnosis is emended to include the presence of simple acuminate processes, illustrated by

Below (1982a, p. 3, text-fig. Id) but not mentioned in his diagnosis. They are generally few in number and intratabular but may be present along one side of the archeopyle margin or bordering the paracingulum. They are most common on cysts that have generally small processes and rare or absent when these are stout.

A few specimens were found which bear a small apical boss (surmounted by a stiff furcate spine in one individual; cf. Davey & Verdier 1974, p. 628) and display a large number of intratabular, simple processes, as well as clearly aligned bi- and trifurcate processes. These to some extent resemble Exochosphaeridium.

A. verdieri differs from A. neptunii in not being as large, and in bearing more numerous and smaller processes that are also sometimes intratabular.

O ccurrence: Atherfield Clay, Hythe Beds.

Genus: Apteodinium E isenack 1958 Type s p e c ie s : A. granulatum Eisenack 1958.

A. granulatum E is e n a c k 1958 emend. S a r je a n t 1985 Plate 5, fig. 17

1958 A. granulatum E isenack, p. 386, pi. 23, figs. 8-14.

1969 A. granulatum - Davey, p. 130, pi. 3, figs. 5, 6.1980a A. granulatum - Morgan, p. 15, pi. 1. figs. 15-17; pi. 2, figs. 1, 2.

H olotype: E isenack 1958, pi. 23, fig. 9. Marne, north Germany; late Aptian.

Remarks: The specimens of A. granulatum encountered are closely comparable to the holotype. They are characterized by having a pear-shaped to broadly oval ambitus, with a short conical, distaily pointed apical horn. The endophragm is smooth, closely adpressed to the periphragm and protrudes slightly into the apical horn. The periphragm is a thick, more or less dense, granular, spongy layer. Parasutures are absent and although a paracingulum is occasionally discernible on the surface of the cyst, it is more usually only observed in optical section as a slight indentation. The parasulcus is devoid of ornament. The structure of the periphragm was originally described by Eisenack as being ‘strongly granular’ and having an ‘alveolar structure’ (translation from German). This was confirmed by Sarjeant (1985) who described it as granular to tuberculate. Davey (1969, p. 130) extended the morphological range to encompass forms possessing short processes linked laterally. M organ (1980a) chose, however, to separate the strictly granular from the more reticulate forms, referring the former to A. conjunctum Eisenack & C ookson 1960, and the latter to A. granulatum. The granular appearance of Eisenack’s holotype of A. granulatum renders this approach untenable.

The Hurlands Farm specimens exhibit the complete gradation of periphragm sculpture described by Davey (op. cit.), ranging from very densely granular forms to those that are less densely but more coarsely granular to tuberculate, to individuals in which the granules merge to form a rugulate to imperfectly reticulate ornament.

It was noted in one assemblage that the development of parasutures defining a gonyaulacoid paratabulation in individuals with a more reticulate periphragm leads to specimens that can be identified as Cribroperidinium conjunctum (Eisenack & C ookson 1960) Helenes 1984, resembling particularly closely those illustrated by H elenes (1984, pi. 1, figs. 7-14). M organ (1980a, p. 15) noted that rare specimens of A. granulatum show ‘complete gonyaulacacean tabulation’; these are also probably referable to C. conjunctum. At the furthest extremity of the spectrum of reticulate forms, specimens are identifiable with Aldorfia vectensh Duxbury 1983.

O ccurrence: Hythe Beds, Bargate Beds.

Apteodinium maculatum Eisenack & C ookson 1960 Plate 5, figs. 13, 14

I960 A.1966b A.1975 A.1976 A.1980a A.1981 A.

maculatum E isenack & C ookson, p. 4, pi. 2, fig. I. maculatum - Sarieant, p. 205, pi. 22, fig. 1, text-fig. 54. maculatum - Brideaux & Mc Intyre, p. 20, pi. 5, fig. 1. maculatum - Norvick Sc Burger, p. 38, pi. 2. fig. 9. maculatum - M organ, p. 16, pi. 2, fig. 5.maculatum E isenack & C ookson 1960 subsp. maculatum Below, p. 26.

H olotype: E isenack & C ookson I960, pi. 2, fig. 1. Oodnadatta Borehole, South Australia; Albian.

Rem arks: Hurlands Farm specimens have been identified as A. maculatum even though they lack the circular markings exhibited by the holotype. In other respects they are similar to the type material. The ‘maculae’ or circular markings are of doubtful taxonomic significance although N orvick & Burger (1976) and Morgan (1980a) considered them to be of diagnostic value. The latter suggested that they originated from biological attack, but were unique to the species and therefore a primary feature. Similar markings have, however, also been seen on Cyclonephelium paucimarginatum C ookson & Eisenack 1962 by Below (1981) and appear to be present on the epicyst of Tricbodinium pelhtum Eisenack & Cookson 1960 (pi. 2, fig. 4). This suggests that their formation is secondary and hence cannot be a diagnostic character (cl. Sarjeant 1966b, Brideaux & McIntyre 1975, Below 1981).

A. maculatum differs from A. granulatum in having a thinner wall, a subcircular to oval outline, and an apical horn that is short, bluntly rounded and conical. In addition, the endocyst of A. granulatum usually protrudes slightly into the apical horn, whereas this does not occur in A. maculatum.

O ccurrence: Weald Clay, Atherfield Clay, Hythe Beds (isolated occurrences).

PalaeoniographicJ. Abt. B. Bd. 210 5

Genus: Baliacaspbaera Drugg 1970 T ype s p e c ie s : B. lompla D rucc 1970.

Batiacaspbaera sp. A Plate 5, figs. 5, 9

D escrip tion : A small, dorso-ventrally flattened spheroidal cyst with a moderately thick-walled autophragm (1-1.5 pm) and an ornament of dense granules which on some cysts lengthen towards the margins into short pila approximately 1 pm high. Archeopyle apical, margin zigzag, with accessory sutures indicating six precingular paraplates and a deep sulcal notch; paratabulation otherwise lacking.

D im ensions: Length without operculum, 28 (37) 47 pm; width, 35 (42) 46 pm (5 specimens). Rem arks: This cyst differs from B. saidensis Below 1981 by being smaller and in having a granular surface.

Membranosphaera sp. A Davey 1979a is similar but has a more complex, spinose ornament.O ccurrence: Hythe Beds, Bargate Beds.

Genus: Chlamydopborella C ookson & E isenack 1958 emend. Duxbury 1983Type s p e c ie s : C. nyei C ookson & Eisenack 1958.

Chlamydopborella nyci C ookson & E isenack 1958 Plate 9, figs. 4, 5

1958 C. nyei C ookson & E isenack, pp. 56, 57, pi. 11, figs. 1-3.1983 C nyei - Duxbury, pp. 41, 43, pi. 3, figs. 4, 8; text-fig. 19.

H olotype: C ookson & E isenack 1958, pi. 11, fig. 1. Roma Series, north Queensland, Australia; Aptian.

Remarks: A number of specimens of C. tiyei have fairly long apical horns similar to those described by D uxbury (1983). These are more common in the Hythe and Bargate Beds and are usually easily distinguished fromC. trabeculosa which was found to occur mainly in the Atherfield Clay. The latter has more densely distributed, finer processes and a more angular outline than C. nyei, which has a more rounded hypocyst and processes that are often open distally.

O ccurrence: Atherfield clay, Hythe beds, Bargate Beds.

Chlamydopborella sp. A Plate 9, figs. 6, 7

D escrip tion : Small, spherical, moderately thick-walled (1.5-2 pm) cyst. Endophragm and periphragm closely adpressed. Periphragm surface micropunctate bearing numerous, evenly distributed, non-tabular, short (5-6 pm) fine processes with briefly bifid distal tips. Occasionally remnants of an ectopbragmal membrane covering the process tips can be discerned. Archeopyle apical, operculum free; accessory sutures indicate the presence of six precingular paraplates and a sulcal notch.

D im ensions: Length without operculum, 30 (34) 37 pm; width, 30 (35) 42 pm (7 specimens).Rem arks: The smaller size, finer processes and less conspicuous ectophragmal membrane distinguish this

species from C/eistospbaeridium buguoniotii.O ccurrence: Hythe Beds, Bargate Beds.

Chlamydopborella spp.Rem arks: This category includes numerous fragmented specimens not readily identifiable with known

species.O ccurrence: Atherfield Clay, Hythe Beds, Bargate Beds.

Genus: Cleistosphaeridium D avey et al. 1966Type species: C. divtrsispinosum Davey et al. 1966.

Cleistosphaeridium sp. A Plate 9, fig. 13

D escrip tion : A species of Cleistosphaeridium with a subspherical ambitus and a smooth to scabrate autophragm which is densely covered by over 100 thin, simple, acuminate, distally closed, non-tabular processes 8- 12 pm long, generally distributed uniformly on each individual. Accessory archeopyle sutures on dehisced specimens indicate presence of six precingular paraplates; otherwise there is no expression of paratabulation.

D im ensions: Length 30 (34) 37 pm; width 30 (35) 45 pm (8 specimens).Remarks: This taxon differs from C.? multispinosum (Singh 1964) Brideaux 1971 in being generally smaller

and in having a smooth wall and non-fibrous processes.O ccurrence: Atherfield Clay, Hythe Beds.

Cleistosphaeridium sp. B Plate 9, tigs. 10, 11

D escrip tion : Skolochorate, spherical, moderately thick-walled (1.5 pm) cyst. Endophragm and periphragm closely adpressed. Periphragm surface microfoveolate, bearing numerous, evenly distributed, fine, simple, acuminate, distally closed hair-like processes 8-12 pm long. Archeopyle apparently apical, but obscured by damage.

D im ensions: Only one specimen was well enough preserved to allow measurements to be made; length, 38 pm (apex compressed); width 48 pm.

O ccurrence: Hythe Beds.

Genus: Coroni/era C ookson & Eisenack 1958 emend. M ay 1980T ype s p e c ie s : C. oceanica C ookson & Eisenack 1958 emend. M ay 1980.

Rem arks: Some difficulty has been encountered in determining the archeopyle type of this genus. It was not specified in the original diagnosis. D avey (1969) first interpreted it as apical. Later he (D avey 1974) emended the diagnosis to include the presence of a precingular opening but also suggested an alternative combination apical/ precingular archeopyle. N orvick & Burger (1976) were uncertain whether the archeopyle is a haplotabular, precingular type or whether the occasional apical breakages represent a true apical/precingular combination or are merely accidental rupturing. M ay (1980) emended the diagnosis of the genus to include a combination type (tA) a + P, and E vitt (1985, p. 154) listed Coronifera among the genera having more than one kind of archeopyle.

In the Hurlands Farm material, specimens of C. oceanica support M ay’s observation that precingular paraplate 3" is the main excystment aperture. Rupturing of the apical region, and even in one instance its entire removal, appears occasionally to have resulted from excystment. Other individuals show, however, a precingular type P3" archeopyle with no apparent apical breakage. Coronifera sp. A (see below) has a large, precingular archeopyle with no apical break but that of C. tuhulosa could not be determined. Breakages in the apical region of C. oceanica seem to have been incurred accidentally during excystment. The possibility exists, as suggested by N orvick & Burger (1976), that apparent variations in the morphology of the archeopyle type of Coronifera are manifestations of the vagaries of preservation of a structurally weak compound archeopyle. As relatively few specimens of Coronifera with archeopyles were encountered, M ay’s emendation is accepted at this stage with some reservation.

Coronifera oceanica Cookson & Eisenack 1958 emend. May 1980Plate 11, tigs. 2, 3

1958 C. oceanica Cookson & E isenack, p. 45, p). 12, figs. 5, 6.1969 C. oceanica - Davey, pi. 8, figs. 8, 11.1974 C oceanica - C ookson & E isenack, p. 72, pi. 24, fig. 15; pi. 28, figs. 13-15.

1974 C. octanica - Davey, p. 47, pi. 2, fig. 6.1976 C. octanica - Norvick & Burger, pp. 53-55, pi. 10, figs. 1, 2.1980 C. octanica - M ay, pi. 1, figs. 5-8.1984 C. octanica - Below, pi. 2, fig. 9.

H olotype: Cookson & Eisenach 1958, pi. 12, fig. 6. Carnarvon Basin, Western Australia; Albian.

Remarks; The Hurlands Farm specimens of C. octanica are very similar in appearance to those from Morocco figured by Below (1984) in that they possess a broad, almost parallel-sided antapical horn 10-14 pm wide. That of the figured holotype is long (17 jam) and narrow. C ookson & Eisenack’s concept of this taxon appears, however, to have changed with time because in 1974 they included in it specimens with broad, stubby antapical horns.

The closely related species C. tubulosa C ookson & Eisenack 1974 differs from the Hurlands Farm specimens of C. oceanica in having a generally narrow (4-7 pm) antapical horn. It is also distinguished by being ornamented with more sparsely distributed, often longer processes arising from a smooth periphragm, and the area around the antapical horn usually being devoid of them. The closely spaced processes arising from the granulate periphragm of C. octanica are commonly joined proximally by low ridges to form an incomplete reticulum. Although the two species can be difficult to separate and intermediate forms occur, the end members are quite distinct.

O ccurrence: Atherfield Clay, Hythe Beds.

Coroni/era tubulosa C ookson & E isenack 1974 Plate 11, fig. 4

1974 C.? tubulosa C ookson & E isenack, p. 73, pi. 28, fig. 12.1982a C. tubulosa - Below, p. 5, pi. 5, figs. 7, 8.1984 C. tubulosa - Below, pi. 2, fig. 10.

H olotype: Cookson & Eisenack 1974, pi. 28, fig. 12. Rivernook Bed, Victoria, Australia; Paleocene.

Rem arks: Cysts referred to C. tubulosa are similar to the holotype in having relatively sparse processes arising from a smooth periphragm, but the distal margin of the antapical horn is slightly serrated rather than smooth. In this respect they are comparable to Below’s specimens of the species.

O ccurrence: Hythe Beds, Bargate Beds.

Coroniftra sp. A Plate 11, fig. 5

D escrip tion : A species of Coroniftra with a two-layered body and a periphragm extended to form a striated tubular, parallel-sided, open-ended antapical horn with an incised distal margin. Periphragm smooth and densely covered in short, hair-like, flexuous, mostly simple, occasionally bifurcate processes. These are non-tabular in distribution but some alignment indicates position of paracingulum, and they are less dense in sulcal zone on ventral surface. Archeopyle large, interpreted as precingular, with no apical breakage apparent; operculum free.

D im ensions: Length of cyst body, 43 pm; width of cyst body, 50 pm; length of antapical horn, 10 pm (1 specimen).

Remarks: The very short processes distinguish this taxon from other species of Coroniftra.O ccurrence: Hythe Beds.

Genus: Cribroptridium N eale & Sarjeant 1962 emend. H elenes 1984Type s p e c ie s : C. sepimentum Neale & Sarieant 1962.

Cribropcridinium sp. cf. C. edwardsii ( C o o k s o n & Eisenack 1958) Davey 1969Plate 6, figs. 7, 8

Rem arks: Specimens assigned to C. sp. cf. C. tdwardsii are characterized by having smooth intratabular areas

and low, apiculate parasutural crests. They differ from the holotype of C. edwardsii in lacking prominent apical spines and in being less robust.

O ccurrence: Atherfield Clay, Hythe Beds, Bargate Beds.

Cribroperidinium spp.Rem arks: A number of morphotypes referable to the genus Cribroperidinium but which cannot be readily

placed in known species have been included here.O ccurrence: Weald Clay, Atherfield Clay, Hythe Beds.

Genus: Exochosphaeridium D avey et al. 1966 Type s p e c ie s : E. phragmites Davey et al. 1966.

Exochosphaeridium? sp. A Plate 10, tigs. 15, 16

D escrip tion : Subspherical, two-layered cyst surmounted by an apical prominence bearing a stiff, trifid- tipped process c. 5 pm long and 3 pm wide. Endophragm protrudes slightly into apical boss. Periphragm surface wrinkled and bears numerous flexuous, flaccid, non-tabular processes 5-12 pm long arising from flared bases, occasionally connected by a narrow pericoel between periphragm and endophragm. Paracingulum weakly indicated by vague alignment of processes. Archeopyle precingular.

D im ensions: Length, 58 pm; width, 52-62 pm (2 specimens).Rem arks: The presence of an apical boss surmounted by a stiff spine is characteristic of Exochosphaeridium,

but in other respects this taxon does not resemble any known species of that genus; hence the tentative reference to it.

O ccurrence: Atherfield Clay.

Genus: Conyaulacysta Deflandre 1964 emend. Sarjeant 1982 Type species: C. jurassica (Deflandre 1938) Norris & Sarjeant 1965 emend. Sarjeant 1982.

Gonyau/acystai kleithria Duxbury 1983 Plate 7, figs. 11-13

1983

Gonyaulacysta sp. cf. G. cassidata (Eisenack & C ookson 1960) Sarjeant 1966aPlate 7, fig. 10

Rem arks: The single specimen compared to G. cassidata exhibits the conspicuous apical cavation characteristic of the species. It differs from the holotype, however, in lacking serrated parasutural crests and a tuberculate endophragm, although this is possibly a function of preservation.

O ccurrence: Hythe Beds.

Genus: Hurlandsia Lister & Batten 1988 Type species: Hurlandsia rugarum (Piasecki 1984) L ister & Batten 1988.

Hurlandsia rugarum (Piasecki 1984) Lister & Batten 1988 Plate 7. figs. 20-23

1984 Mtndicodinmm rugarum P iasecki, p. 150, pi. 4, figs. 1-5, 7, 8, text-fig. 5.1988 H. rugarum (Piasecki 1984) L ister & Batten, p. 508, figs. 2A, B, 3A-F, 4A-D, 5A, B, F.

H olotype: P iasecki 1984, pi. 4, fig. 2, Jydegard Formation, Bornholm, Denmark; late Ryazanian - early Valanginian.

D escrip tion : Proximate cyst, angular to rounded hexagonal ambitus. Wall single-layered, faintly striated or scabrate, often folded and torn. An incomplete paratabulation of gonyaulacacean affinity is weakly defined by partially developed ridges or folds. A distinct, slightly laevorotatory paracingulum 4-5 pm wide is always present. A short, blunt apical horn, with three to four apical paraplates more or less clearly outlined, is usually visible but may be present only as a low prominence. Pre- and postcingular parasutures are generally incomplete