110 



ZOOLOGY 



ostreum (Fig. 105), found in the mantle chamber of the 

 oyster, is eaten by us together with the oyster or separately. 



FIG. 104. Platyonichus ocellatus, lady oral). Reduced to one-third. 



Photo, by W. H. C. P. 



The fiddler crabs are representative of the square crabs. 

 These are the familiar animals which crowd salt marshes 

 and run sideways to and from their burrows. One claw is 



much larger than the other. 

 When the crab is disturbed, 

 the large claw is brandished 

 in a manner which has been 

 likened to the movements of 

 a riddle as one plays upon 

 it. Crelasimus pugnax is the 

 most abundant species, and 

 ranges from Cape Cod to the Gulf of Mexico. Together 

 with Cambarus it does much damage by burrowing in the 

 levees of the Mississippi River (Fig. 100). 



FIG. 105. Pinnotheres oxtreum. X 4 

 From Rathbui). 



