Description:
The common mud crab, Panopeus herbstii, also known as the Atlantic mud crab, grows to 1.4 - 2.5 inches in carapace length.  Color is olive-brown to gray or slate.  Chelae are generally darker in color than the carapace, and sometimes spotted in a brown-red color along the uppermost half.  The fingers of the chelae are black, with the moveable finger of the major claw having an enlarged white tooth at its base. The lower portions of the chelae are light in color, and may be shades of pink, yellowish or purple-red.  First and second teeth of the carapace are coalesced and separated by a shallow, rounded notch, with other teeth somewhat curved toward the anterior.  The fifth tooth is significantly smaller than the forth, and is hooked forward. Lower outer surfaces of the palms are lightly colored in

Habitat:
Common mud crabs are associated with muddy or hard bottom types in the shallow intertidal and subtidal zones to depths of approximately 60 feet.  They occur on mudflats, oyster reef, rock or shell rubble and are also observed among mangrove roots, on coral reefs, and in seagrasses. 

Similar Species:
The knotfinger mud crab, Panopeus lacustris, is similar in size and appearance to common mud crabs.  However, its first and second carapace teeth, while coalesced, are separated by a deep, rounded notch;  and its other carapace teeth tend toward being rectangular at their tips. 

Range:  
The common mud crab ranges from approximatly Boston, Massachusetts south to Bermuda, Florida, the West Indies, and the Gulf of Mexico to Brazil.