. Bulletin of the British Museum (Natural History), Geology. 2o6 KIMMERIDGIAN DINOFLAGELLATES & ACRITARCHS than those of the specimens described earUer (overall length 65JX, breadth 42[i.) but its proportions are similar. Yet further specimens of this type must be located before nomenclatural proposals can justly be made. Gonyaulacysta sp. B Plate 4, figures 2-3, text-figure 10 Description: Only one specimen of this species has so far been observed. It possesses a subspherical cyst, bearing a moderately well developed apical horn. The strongly helicoid, laevorotatory cingulum divides the c


. Bulletin of the British Museum (Natural History), Geology. 2o6 KIMMERIDGIAN DINOFLAGELLATES & ACRITARCHS than those of the specimens described earUer (overall length 65JX, breadth 42[i.) but its proportions are similar. Yet further specimens of this type must be located before nomenclatural proposals can justly be made. Gonyaulacysta sp. B Plate 4, figures 2-3, text-figure 10 Description: Only one specimen of this species has so far been observed. It possesses a subspherical cyst, bearing a moderately well developed apical horn. The strongly helicoid, laevorotatory cingulum divides the cyst into two more or less equal parts: the hypotract is somewhat flattened at the antapex. The sulcus is sigmoidal and narrow. Tabulation: 4', 6", 6c, 5'", ip, ?ipv and i"". The apical plates i' and 4' are small and elongate; together with plates 2' and 3', they form the apical horn. The precingular plates are quite large. Plate 3" is lost in archaeopyle formation. On the hypotract, crests demarcate five postcingular plates. Plate i'" and 5'" are reduced because of the presence of posterior plates, but the other postcingular plates are large. A single antapical plate occupies the antapex. The wall is moderately thin, its surface finely granular and in part tuberculate. Crests on the plate boundaries are delicate; the denticulation is very deep, virtually giving the crests the appearance of a row of bifid spines. Figured specimen: sHde , Slide WB 15, from Geological Sui'vey Borehole, Warlingham, Surrey, at 2635 ft 3 in. depth. Middle Kimmeridgian (Elegans Zone).. 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)


Size: 1502px × 1664px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: ., bookauthorbritishmuseumnaturalhistory, bookcentury1900, bookcoll