Hemigrapsus nudus

The Purple Shore Crab

Phylm Arthropoda
Subphylum Crustacea
Class Malacostraca
Subclass Eumalacostraca
Order Decapoda
Suborder Pleocymata
Infraorder Brachyura
Family Grapsidae 
Genus Hemigrapsus
Species nudus

Description: Size up to 5.6 cm; color is dark purple, can occasionally be olive green or reddish brown; carapace has three teeth; pincers have distinct purplish-red spots; legs are hairless.

Habitat: Found on rocky or gravelly beaches.

Natural History: Feeds primarily on sea lettuce and other green algae, but also feeds upon dead animals. They contribute greatly to keeping the beaches clean by scavenging.