THE CRUSTACEA OF NEW JERSEY. 393 



eastern coast, the stone crab (Menippe) of the southern coast, 

 and the common crab (Cancer niagister) of the western coast, 

 are well known. 



Key to the families. 



a. Antennules folded transversely or obliquely transversely ; outer max- 

 illipeds usually not overlapping epistome. 



b. Last pair of legs not modified for swimming. pilumnid.^ 

 bh. Last pair of legs usually modified for swimming, last two joints com- 

 pressed, very broad and paddle-like. portunid/1-; 

 aa. Antennules folded longitudinally ; outer maxillipeds long, overlapping 

 epistome. cancrid^ 



Family PILUMNID.^. 

 The Mud Crabs. 



Carapace commonly transverse and convex, antero-lateral 

 edges arcuate, armed with several lobes, teeth or spines. Front 

 of moderate width, generally not projecting over first antenn3e 

 and bases of second, latter seldom excluded from inner hiatus 

 of orbits. 



These crabs are transversely oval or hexagonal, and are 

 without either projecting spines or natatory feet. They include 

 many small species living among rocks or sponges, under stones, 

 or in muddy places. Most of our forms occur on the oyster-beds 

 of the bays and sounds, where they live among the dead oyster- 

 shells, when the latter remain in clusters with the valves attached 

 though rigidly open. The crabs are slow in their movements, 

 and not agile. They apparently remain a long time in one place 

 and wait for such food as happens their way. They often live 

 in holes in the banks above the mark of high tide, like Uca and 

 Sesariiia. In deeper water they frequent almost any objects af- 

 fording some measure of concealment, such as dead shells, clus- 

 ters of oysters, corals, sponges, etc. Many are distinguished in 

 such habitats only with difficulty. 



