Charactoceras estonicum Foerste 1924

Genus Charactoceras Foerste, 1924 Type species Trochoceras (?) baeri Meek & Worthen, 1866, Richmond, Indiana, USA, Whitewater Formation, late Katian, Ordovician; by original designation. Diagnosis Closely coiled, rapidly expanding conchs with dorsally impressed whorl cross section, with flattened venter and rounded sides that converge towards the dorsum; sutures essentially straight laterally but forming broad ventral and dorsal lobes; surface with transverse growth lines that form distinct hyponomic sinus on venter, and transverse ribs in early stages only; siphuncle between center and venter, with cyrtochoanitic septal necks, empty; segments expanding slightly within camerae.” (Adopted from Sweet 1964a.)