Appearance
Like the other members of the family Cancridae, the slender crab has a very broad and oval carapace with dull, tooth-like protrusions toward the front of the carapace. Female crabs can be distinguished from males by a broad tail flap on their undersides, which are used for protecting their eggs when they are gravid. The slender crab carapace is usually olive brown, and its legs vary from yellowish brown to purple. M. gracilis only grows to a width of about 3.5 inches (9 cm) and resembles a juvenile M. magister (dungeness crab). Often the two species can be confused, as M. gracilis looks very similar to a juvenile Dungeness crab. They can readily be distinguished from each other, though M. gracilis has a notch behind the widest point of its carapace that M. magister lacks, and the top joint of its pincers are not serrated like those of M. magister.