7 8 Descriptive Zoology. 



Crabs. Though differing considerably in appearance, 

 crabs have the same essential structure as crayfishes and lob- 

 sters. The cephalothorax is broad instead of being rela- 

 tively long and narrow. The abdomen is kept folded under 

 the cephalothorax, and is not used in swimming, almost its 

 only use being to protect the eggs in the female. As in the 

 preceding forms, there is the hard protecting crust ; stalked 

 eyes; several mouth parts ; five pairs of large thoracic ap- 

 pendages, the first pair armed with big pinchers ; gills on 



FIG. 50. SHRIMP. 



the sides under cover of the carapace ; and the same general 

 manner of life. Crabs are great scavengers ; and if, while 

 at the seaside, one wishes to clean a skeleton, if he puts it 

 into a box guarded by slats, with spaces just wide enough 

 to let crabs in, they will do the rest. Crabs may be caught 

 by tying a piece of meat to a string and letting it down off 

 almost any wharf or rock into the water. When the crab 

 takes hold with the pinchers he will usually hold on till he 

 reaches the surface ; and while he may be lifted out on the 

 wharf or bank, it is safer to use a net when he is brought 

 to the surface. Though most crabs are good to eat, and 

 many kinds are so used, the one most eaten is the blue crab 



