Genus Rizosceras Hyatt, 1884

Type species

Orthoceras indocile Barrande, 1866 from Kocorc, Bohemia, Czech Republic, Middle Silurian; by original designation.

Diagnosis

Compressed, rapidly enlarging, straight to faintly curved brevicones with hyponomic sinus and distinct, faintly rugose transverse surficial ornament; siphuncle ventrally positioned near conch margin; septal necks cyrtochoanitic; siphuncular segments cardioid in dorsoventral section. (Adopted from Sweet 1964b.)