. Bulletin of the British Museum (Natural History), Geology. . Fig. 13. Gonyaulacysta sp. A. Tabulation and the archaeopyle formation (plate 3" remains attached). Left, ventral view ; right, dorsal view. xc. 1280. undescribed species of Gonyaulacysta. These two specimens differ from all previously described species in their tabulation and spiny surface. Gonyaulacysta sp. B (PL 6, fig. 3 ; Text-fig. 14) Description. The broadly ovoidal theca terminates in a poorly developed apical horn. Tabulation: 4', la, 6", 6c, 6" ', lp, lpv and 1" ". Spiny crests of moderate height
. Bulletin of the British Museum (Natural History), Geology. . Fig. 13. Gonyaulacysta sp. A. Tabulation and the archaeopyle formation (plate 3" remains attached). Left, ventral view ; right, dorsal view. xc. 1280. undescribed species of Gonyaulacysta. These two specimens differ from all previously described species in their tabulation and spiny surface. Gonyaulacysta sp. B (PL 6, fig. 3 ; Text-fig. 14) Description. The broadly ovoidal theca terminates in a poorly developed apical horn. Tabulation: 4', la, 6", 6c, 6" ', lp, lpv and 1" ". Spiny crests of moderate height rise up on the plate boundaries. A slightly helicoid, laevorotatory cingulum of moderate breadth divides the theca into two unequal parts: the epitract is larger than the hypotract, almost § of the shell length. The hypotract is dome-shaped. The sulcus is moderately broad, extending on both epitract and hypotract to the same length. The surface of the shell is densely granular. Apical plate 1' is elongate, its anterior and posterior ends being narrow ; together with plate 3', it forms the apical horn. Plate 2' is quite large ; 4' is the smallest of the apical plates. The single anterior intercalary plate ia is large ; as a result plate 6" is reduced. Plate 1" is long and narrow ; plates 2", 3", 4" and 5" are large. Plate 1" 'is quadrate, as small as the single sulcal plate. All the other postcingular plates are relatively large. Posterior intercalary plate ip is small and triangular,. 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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