Octamerella

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 sinusus, four on each side, and a narrow mid dorsal salient. The two ventral-most sinus pairs are typically the larges while the dorsal-most pair is short and wide, forming a circular opening. (Sweet, 1964)