These small intertidal crabs are characterized by the black tips of their chelipeds (claws) and bumpy carapace. They prefer to reside under rocks, especially those on gravel substrate. They are omnivores. Black-clawed crabs are frequently parasitized by a rhizocephalan barnacle which extends its body through the circulatory system as it grows and hijacks the reproductive system of the crab, replacing the crab's eggs with its own. (wallawalla.edu, Moran 2026)