6o THE LIFE OF CRUSTACEA 



The other tribe belonging to this section is the 

 Eryonidea, comprising a number of small lobster-like 

 forms living in the deep sea. They have pincer- 

 claws on the first four, or on all five, pairs of legs, 

 and they are of special interest on account of their 

 geological antiquity. 



The section Astaciiva contains only a single tribe, 

 Nephropsidea, formed by the true Lobsters and the 

 fresh-w^ater Crayfishes. They have pincer-claws on 

 the first three pairs of legs, and the first pair are 

 much larger than the others. 



The third section of the Reptantia, the Anomura, 

 comprises forms in which the abdomen is variously 

 modified, being either bent upon itself or, if extended, 

 more or less soft and feebly armoured. The last pair 

 of legs are commonly reduced in size, and not used 

 in v^alking. The members of the four tribes com- 

 posing the section differ widely in their general 

 appearance. 



The Galatheidea (Plate VL) are small, flattened, 

 lobster-like animals which have the abdomen bent 

 under the body. In one family {Porcellanidcs) the 

 animals have quite the appearance of little Crabs 

 (see Fig. 41, p. 113), but they may be distinguished 

 from the true Crabs (Brachyura) by the fact that 

 there are only three pairs of walking legs behind the 

 great chelae, the last pair of legs being very small 

 and carried folded up at the sides of the body, or 

 even within the gill chambers. 



