Gatunek typowy
Orthis irregularis Roemer, 1844; Mid Devonian (Givetian); Gerolstein, Germany.

Opis

Ventral valve moderately to strongly convex profile and dorsal valve first flat but geniculate anteriorly with unequally parvicostellate weak ornament; ventral muscle field weakly impressed anteriorly with bilobed diductor scars separated by low, wide myophragm; denticles along most of valve width; erect and posteriorly directed cardinal process lobes; field of dorsal muscle bounded by low ridges and one pair of dorsal side septa present with anterior ends sometimes curve out laterally; weak dorsal median ridge developed centrally.

Synonimy
Chuanostrophia Xian in Xian et al., 1988

Zasięg czasowy

Devonian (Emsian to Givetian); Euroasia.

Literatura