Octamerella is an extinct genus of prehistoric nautiloids from the oncocerid family Hemiphragmoceratidae that lived in what is now Europe and North America during the Middle Silurian.
Octamerella has a breviconic shell and a mature aperture that is contracted so as to have four pairs of dorsolateral sinuses, four on each side, and a narrow mid-dorsal salient. The two ventral-most sinus pairs are typically the largest, while the dorsal-most pair is short and wide, forming a circular opening.Sweet, 1964
References
Sweet, W.C. 1964. Nautilodea-Oncocerida; Treatise on Invertebrate Paleontology, Part K; Geol Soc of America and Univ Kansas Press, Teichert & Moore eds. Sepkoski, J.J. Jr. 2002. A compendium of fossil marine animal genera. D.J. Jablonski & M.L. Foote (eds.). Bulletins of American Paleontology 363: 1–560. Sepkoski's Online Genus Database (CEPHALOPODA) Fossilworks: Octamerella