232 POPULAR HISTORY OF THE AQUARIUM. 



are much mottled^ with whitish spots and darker markings 

 symmetrically arranged. 



The carapace is broader than long^ and widest in front. 

 The front edge between the eyes is five-lobed, and its con- 

 tinuation on each side of the eyes is notched into four or 

 five teeth. The front pincers are large, and all the claws 

 pointed. In the last pair of legs however may be observed 

 a disposition in the last joint and claw to spread and flatten. 

 For though the Common Crab does not swim, he some- 

 times gives a kind of swimming jump through the water, 

 using the hind legs as flappers. In the Swimming Crabs 

 we shall find this character developed more fully, and then 

 the liind legs are used as swimming paddles. 



Placing a Crab and a Lobster side by side, we should be 

 ready at first to pronouce them very different animals. Their 

 general figures are almost the opposites of each other; but 

 when we come to compare the parts we shall find the differ- 

 ence less than we suspected. The great dissimilarity of form 

 arises principally from this, — that in Crabs the abdominal 

 portion, or tail, is not largely developed, and instead of 

 being a free cylindrical body, moving in joints, it is flattened 

 and doubled up in front of the thorax, so that only one or 

 two narrow joints of it are seen from above ; whereas in a 



