Wikipedia
Cumingsoceras
Cummingsoceras is a barrandeoceroid genus within the Tarphycerida, included in the family Uranoceratidae. Its shell is a rapidly expanding gyrocone of about 1.5 narrowly separated whorls.
The surface is faintly cancellated by slight longitudinal lines that cross growth lines which define a deep hyponmic sinus. The siphuncle is small, subcentral, and with recumbent necks.
Cummingsoceras is known from the middle Silurian of Indiana and Illinois.