Lopha species have thick, strongly ribbed shells with unequal valves.

Their widely-known fossils show a ribbed spiral-form shell, in the end compartment of which lived the tentacled animal.

Docidoceras has a broad,finely ribbed, evolute shell with a depressed whorl section.

It has a strongly ribbed shell, with the lower valve curving outwards and the upper valve being flat.

Individual animals have brown ribbed shells, which darken to black with age.

Wide, ribbed shells with a small beak projecting from the upper valve, the lower valve is deeply convex.

Since the shell grows at the margins, a ribbed shell is produced, with fine or coarse ribs according to the species.

Dactylioceras has a strong, ribbed shell.

The ribbed shells of this species attain a length of 10 cm.

The ribbed shells usually grow to attain a 10 cm length, and 13 cm at most.