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Gonyaulacysta fetchamensis

Gonyaulacysta fetchamensis Sarjeant, 1966

Now Cribroperidinium. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly (and now) Cribroperidinium.
Holotype: Sarjeant, 1966, pl.15, figs.1-2, text-fig.33 and Jan du Chêne et al., 1986, pl.20, figs.1-4
Locus typicus: Fetcham Mill, Surrey, England
Stratum typicum: Cenomanian

Original diagnosis: Sarjeant, 1966, 128
A Gonyaulacysta having an ovoidal theca with strong, blunt apical horn formed by periphragm only. Tabulation 3-?4", 1a, 6", 6c, 7""", 2p, 1""""; sutures in form of low but well-marked, rather fibrous crests giving rise occasionally to short, blunt spines. Cingulum narrow, strongly spiral; sulcus broad, sunken. Shell surface densely granular.
Dimensions: holotype: overall length 125 µm, breadth 108 µm; shell length 95 µm, breadth 98 µm; length of horn c.25 µm.

Original description: Sarjeant, 1966, p. 128-129
This species is extremely infrequent: of three specimens encountered, one (the holotype) is well preserved, the other two are severely damaged. The shell is broadly ovoidal, giving rise to a strong, blunt apical horn; this horn is formed by the periphragm only and constitutes what is effectively an apical pericoel. There are certainly three and possibly four apical plates, presence of a crest separating plates 3" and 4" being unconfirmed. Plate 1" is unusually large and club-shaped.
Six precingular plates are present, with plate 6" reduced to accommodate a subtriangular anterior intercalary plate. Seven postcingular plates are present.
Plates 1""" and 2""" are reduced to accommodate a large posterior intercalary plate, and plate 7""" is also reduced to accommodate a second, smaller intercalary plate. (The crest separating plates 5""" and 6""" is somewhat torn.) The antapex is occupied by a single plate of moderate size.
The cingulum is narrow, forrning a laevorotatory spiral such that its two ends differ in antero-posterior position by almost three times its width. The ends of the cingulum are widely separated by a very broad sulcus, which widens further in its posterior portion. The crests are fibrous in nature, with close-set slits in places: they give rise to occasional short spines. In the holotype a broken line of " tubercles ", like an embryonic crest, crosses plate 5"; this was not observed in the other specimens.
A precingular archaeopyle is formed by loss of the large plate 3". In the holotype, the region round the archaeopyle is somewhat folded.
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