[3] The carapace is a badge-like shape similar to a police officer's badge or shield; hence the secondary name shield-backed crab.

The front of the crab has a protrusion called a rostrum, extending the carapace and is used in feeding.

It is found along the Pacific Coast of North America from southern Alaska to northern Mexico.

These crabs are also common in lower intertidal zones in beds of algae or eelgrass.

Adults are frequently eaten by cabezon, gulls, sea otters, and staghorn sculpins.

During this molt, the barnacle then pushes its reproductive sac through the crab's molt-softened carapace.

Females may carry eggs during most parts of the year[3] but are rarely seen in south Puget Sound in May, September, and October.

They begin bright orange, change to red as they mature, and hatch when they are a grayish purple color.

[4][3] This crab has a terminal molt which may end up covered with barnacles, limpets, or bits of algae.