It was first described to science by Johan Hjalmar Théel in 1886[1] reporting on the sea cucumber specimens brought back by the Challenger expedition.

[5] This is a shallow water species living on rocky bottoms in the intertidal zone, often in association with mussel beds.

Its close association with mussel beds, including those of Mytillus californianus, suggests that feces from these bivalves may form an important part of its diet.

The skin of the females in contact with the egg mass is highly vascularized, suggesting that the adult provides nutrients to the developing young.

This latter species extends from the southernmost range of the tiny black sea cucumber in British Columbia to Southern California.

Detailed examination of the bony plates in the skin, the ossicles, suggests a gradual change over the geographic range of the two species, rather than a sharp difference at the boundary between the two.