170 



SYSTEMATIC ZOOLOGY 





The true crabs (Figs. 163 and 164) are mostly marine, though 

 some occur in fresh water, some live on sandy beaches just 

 above the water, while some in the tropics are essentially land 



a.Ttl.1 



Tnazp 



Fig. 163. Cancer pagurus. A, dorsal aspect : B, ventral, ant.r, antennule ; ant. 2, antenna; 

 abd.i, j, 7, abdominal segments; E, eye stalk: /./, I.5, legs; mxp, third maxillipeds. 

 (From Parker and Haswell's Manual.) 



animals, going to the sea only during the breeding season, when 

 they frequently migrate thither in very large numbers. The 

 largest crab known is found in Japan ; the body is about thirty 

 centimeters in diameter, but the legs are so long that when 



