108 



ZOOLOGY 



seen stalking over such uneven surfaces, the advantage of 

 these stilt-like legs is at once evident. The surface of the 

 body of some species of spider-crabs is hairy, entangling 

 inorganic matter, while hydroids, barnacles, and algse attach 

 themselves to the shell. Libinia emarginata and dubia, 

 the former ranging from Maine south, and the latter from 

 Cape Cod to the Gulf of Mexico, are our two species which 



FIG. 101. Libinia dubia. One-third nat. size. Photo, by W. H. C. P. 



undergo such concealment. The great Japanese spider- 

 crab is said to be the largest of all the Crustacea, some 

 individuals measuring, from tip to tip of the first pair of 

 legs, 18 to 20 feet. 



The edible crab is a typical arched crab. It is so called 

 because the carapace is arched in front. The carapace is 

 also broader than long, and narrower behind than in front. 



