Description
Males can easily be distinguished from the females by their differently shape carapace. When seen from above, the eyes of the male pea crab are visible, at the female the carapace is round and the eyes can not be seen from the top. The males also have a hard carapace, where the females have a more leather like shell. The male is smaller than the female.

Size
Females are 15 mm long and males only 8 mm.

Colour
The female is white, cream to brownish. The male is often darker with dark spots.

Habitat
Lives in clams and mussels, but also in sea squirts. They are no parasites, their are no negative consequences for the host. Whether the host has any profit from its guest, can be doubted.

Distribution
From south Scandinavia til south of Spain and the entire Mediterranean.