Cyclostomiceratidae

Cyclostomiceratidae, from Ancient Greek κύκλος (kúklos), meaning "circle", στόμα (stóma), meaning "mouth", and κέρας (kéras), meaning "horn", is an extinct family of Early Ordovician, (Cassinian), ellesmerocerid cephalopods characterized by short, essentially straight shells, a fairly rapidly expanding phragmocone and a ventral siphuncle in which septal necks are almost non-existent and connecting rings are thick and layered. As typical of the Ellesmerocerida, chambers are short, septa close spaced.