crioceras

from The Century Dictionary.

• noun A genus of tetrabranchiate cephalopods, of the family Ammonitidæ, or made type of a family Crioceratidæ, containing discoidal ammonites having the whorls discrete: so called from the resemblance to a ram's horn. The species are numerous. Also Criocera, Crioceratites, and Criocerus.