Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . X B. Fig. 19. Pterotrigonia rogersi (Kitchin), x 1. A-B. Dorsal and lateral views of PEM-1465 Lateral view of the lectotype in the South African Museum. LOWER CRETACEOUS TRIGONIOIDA FROM THE ALGOA BASIN 37 (H/L = 0,63-0,71) and posteriorly produced. Umbones prominent, broad,strongly incurved, situated about one-quarter of the shell length from theanterior, with slightly opisthogyrous beaks. Anterior margin broadly convex,flattish, passing into the very broad, gently convex ventral margin. The postero-dorsal margin
Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . X B. Fig. 19. Pterotrigonia rogersi (Kitchin), x 1. A-B. Dorsal and lateral views of PEM-1465 Lateral view of the lectotype in the South African Museum. LOWER CRETACEOUS TRIGONIOIDA FROM THE ALGOA BASIN 37 (H/L = 0,63-0,71) and posteriorly produced. Umbones prominent, broad,strongly incurved, situated about one-quarter of the shell length from theanterior, with slightly opisthogyrous beaks. Anterior margin broadly convex,flattish, passing into the very broad, gently convex ventral margin. The postero-dorsal margin is shallowly concave, and the respiratory margin subtruncate witha distinct posterior gape. The ligament pit is about 17 per cent of the shell length. The sunken escut-cheon is very broad, conspicuous, lanceolate, with fine, beaded, obliquelytransverse costellae that become obsolete before reaching the commissure. Inthe nepionic stages, the costellae of the escutcheon extend to the median longi-tudinal groove of the area, giving the inner area a beaded appearance for up to1
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Keywords: ., bookauthorsouthafr, bookcentury1800, bookdecade1890, bookyear1898
