DECAPOD CRUSTACEA. 167 



some economic value as food, but all of them are important 

 as scavengers. In America " soft-shelled crabs" are 

 prominent in our markets at the proper season of the year. 

 During the rest of the time this crab, known as the "blue 

 crab," has as hard a shell as any crab, but when the proper 

 moment comes the shell splits across the hinder margin, 

 and out from this opening comes the body covered only 

 with the thinnest skin, and at this time alone is it a " soft 

 shell." All other crabs molt or shed their skin in the same 

 way, the new skin rapidly growing hard again, but the 

 blue crab is the only one taken in sufficient abundance 

 at this time to be of economic importance. 



