. Bulletin of the British Museum (Natural History) Geology Supplement. n8 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS Gonyaulacysta episoma sp. nov. PL 13, figs. 9, 10 ; Text-fig. 27 Derivation of name. Greek, episomos, bulky, fat—referring to the rotund shell shape. Diagnosis. A Gonyaulacysta with spherical to broadly ovoid shell with strong apical horn of moderate length. Tabulation 4', ia, 6", ?5c, 6'", ip, 1 , 1"". Crests consisting of rows of thin spinelets connected distally by trabeculum ; an extremely delicate membrane stretching between spinelets and trabecula.
. Bulletin of the British Museum (Natural History) Geology Supplement. n8 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS Gonyaulacysta episoma sp. nov. PL 13, figs. 9, 10 ; Text-fig. 27 Derivation of name. Greek, episomos, bulky, fat—referring to the rotund shell shape. Diagnosis. A Gonyaulacysta with spherical to broadly ovoid shell with strong apical horn of moderate length. Tabulation 4', ia, 6", ?5c, 6'", ip, 1 , 1"". Crests consisting of rows of thin spinelets connected distally by trabeculum ; an extremely delicate membrane stretching between spinelets and trabecula. Cingulum strongly spiral ; sulcus broad and short, stretching from about mid-point on epitheca to about mid-point on hypotheca. Surface densely granular ; very few spines occasionally present. Horn with trifurcate appearance produced by high crest bounding plate 4'. Holotype. () slide ¥.51730(1). Speeton Clay, Shell West Heslerton Borehole No. 1, West Heslerton, Yorks., at 19-25 metres depth, Lower Cretaceous (Upper Barremian). Dimensions. Holotype : overall length So[i, breadth 74^ ; shell length yo\L, breadth 68[jl ; horn lOfx in length ; crests in height ; cingulum \i broad. Range of dimensions : overall length 80-95^, horn length io-i8[jl, breadth 6o-8o[x. Description. An abundant species at this horizon, some 30 specimens having been examined. All show some degree of distortion as a result of compression of the originally spherical, fairly thin-walled shell. The horn is short, strongly tapering and pointed ; it is tipped by plate 4', the high crest bounding this plate producing a. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London : BM(NH)
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