590 



ZOOLOGY 



SECT. 



specialisation known among the Crustacea. The cephalothorax 

 (Fig. 468) is always of great proportional breadth, and is frequently 

 much broader than long. The abdomen, on the other, hand is greatly 

 reduced, its sternal region is uncalcified, and it lies permanently 



rrtazp 





FIG. 46^. Cancer pagurus. A, dorsal, B, ventral aspect, ant.l, antennule ; ant.2, antenna 

 abd.l, dbd.3, abd.7, abdominal segments ; S, eye-stalk ; l.l, 1.5, legs ; mxp.3, third inaxilli 

 pedes. (A, after Bell.) 



flexed in a groove on the very broad thoracic sterna, so as to be 

 often quite hidden in a view from above. In correspondence with 

 this the pleopods are much reduced, the male retaining only two 

 pairs as copulatory organs, the female four pairs for the attachment 

 of the eggs. The uropods are absent, so that there is no tail-fin 



