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 largest, while the dorsal-most pair is short and wide, forming a circular opening.