antennu.l 

 epistome 



postorbital tooth 

 .anterolateral teeth. 



VENTRAL 



Figure 2. — Diagram of crab in dorsoventral views showing structures and terms used in key. 



KEY TO MARINE DECAPOD CRUSTACEANS OF THE NORTHEASTERN UNITED STATES, 



INSHORE AND SHELF WATERS 



General form shrimplike, usually compressed (if depressed, with pleura of second abdom- 

 inal segment overlapping those of first segment); abdomen well developed; pleopods 



always present and in full number (5 pairs), used for swimming shrimps 



Suborder Natantia 



General form lobsterlike or crablike, usually depressed; abdomen either well developed 

 (asymmetrical in a few species adapted for living in moUusk shells) or greatly reduced 



in size; pleopods often reduced or absent, not used for swimming lobsters; mud 



shrimps; hermit, porcellanid. and mole crabs; true crabs Suborder Reptantia 



18 



2 (7 ) Pleura of second abdominal segment not overlapping those of first segment 



Section Penaeidea 3 



