Rodzaj Proacirsa Cossmann, 1912
Gatunek typowy Opis The protoconch consists of about 1.5 whorls, is heterostrophic and almost coaxial. The early teleoconch has two or three spiral ribs; the adapical rib is distinctly weaker than the abapical spiral ribs. The spiral ribs are intersected by numerous axial ribs; the intersections are more or less nodular. After a few teleoconch whorls, the ornament fades. Only in some cases, remains of a spiral ornament are present on the last whorls. The base is moderately convex and is ornamented with broad spiral ribs. Synonimy Zasięg czasowy Early Jurassic (Pliensbachian) - Early Cretaceous (Valanginian). Literatura Cossmann, M. 1912. Essais de paléoconchologie comparée, vol. 9. 215 pp. J. laMarre & Cie., Paris. |
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