540 



ZOOLOGY 



ECT. 



In the Bracliyura, or true Crabs, we reach the highest degree of 

 specialisation known among the Crustacea. The cephalothorax 

 (Fig. 427) is always of great proportional breadth, and is frequently 

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



B 



CLTLl.1 



FIG. 427. Cancer pagurus. A, dorsal ; B, ventral aspect, ant.l, antennnle ; ant.2, antenna; 

 abd.l, abd.S, <iJ></.7, abdominal segments; , eye-stalk ; l.l, l.Z, legs; ,,u^.J, third nuixilli- 

 pedes. (A, After Bell.) 



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

 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 ^leopods are much reduced, the male retaining only two 

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





