Cyrtogomphoceras Foerste 1924

Genus Cyrtogomphoceras Foerste, 1924 Type species Oncoceras magnum Whiteaves, 1890, East Selkirk, Selkirk Member, Red River Formation, late Katian, Ordovician, by original designation Diagnosis Compressed endogastric cyrtocones with fusiform outline in lateral view; rapidly expanding in adoral part of mature phragmocone and/ or basal part of mature body chamber; mature body chamber gibbous, conically contracted; aperture with hyponomic sinus; sutures with shallow lateral lobes, sloping increasingly toward the antisiphuncular side of the conch in later growth stages; siphuncle large, not strictly marginal, with short cyrtoconic septal necks, thick connecting rings, and endosiphuncular bullettes, cameral deposits absent. (Adopted from Teichert 1964b.)