What is "monocyrtoceras"

Monocyrtoceras is an armenoceratid, ( Cephalopoda), from the Middle Silurian of North America, (Wisconsin), with a gently curved shell and a siphuncle like that of Elrodoceras.

According to Teichert, 1964, in the Treatise part K, Monocyrtoceras along with Elrodoceras and Armenoceras forms one of the two branches of the Armenoceratidae.