218 ANIMALS OF THE SEASHORE 



Reptantia 



Lobster and crab-like forms; divided into four 

 groups : 



1. PaUnura: Abdomen extended; rostrum short 

 or wanting; cheliped (large claw) absent. Not 

 represented in this region — Spiny Lobster. 



2. Astacura: Abdomen extended; rostrum short; 



cheliped present. Lobster. 



3. Anomura: Abdomen usually bent under cephalo- 



thorax or more or less spirally twisted and con- 

 cealed in a shell; last pair of thorasic legs re- 

 duced in size and extended upwards. Hermit 

 Crabs, Hippa, etc. 



4. Brachyura'. Abdomen shorter than cephalothorax 



and permanently folded under it; no uropod 

 (tail fin). True Crabs. 



According to older classification the two divi- 

 sions were Macrura and Brachyura — the former in- 

 cluding the shrimp, lobsters, hermit crabs and the 

 like, while the latter included the true crabs. The 

 term Macrura is not used today while the term 

 Brachyura is still used for the crabs but is a sub- 

 division of Reptantia. 



Natantia 



(True Shrimp) 



Crago septemspinosus Say . (Shrimp) 



(Crago vulgaris Verrill) 



Fig. 39 



The common shrimp of the New Jersey coast. 

 It occurs in great numbers in shallow water from 



