Gatunek typowy
Orbicula forbesii Davidson,1848; Silurian, Wenlock; England

Opis

Shell strongly dorsibiconvex to convexoplane, subcircular with ornament of both valves usually with well-developed, concentric fila; dorsal valve conical to subconical with apex variably positioned; ventral valve low subconical to gently concave, pedicle track narrow, closed anteriorly by listrium; foramen at posterior end of listrium as internal tube to open in front of posterior margin.

Synonimy

Zasięg czasowy

?Ordovician, Silurian–Permian; cosmopolitan (stratigraphic and geographic range uncertain)

Literatura