CRUSTACEA. 



205 



These singular organs, although entitled to be 

 considered as jaws, so far as their use would indicate, 

 are no less obviously merely modifications of jointed 

 feet ; they are, therefore, termed " foot-jaws." ' 



FlG. 158. COMMON LOBSTEK. 



The pair of legs which comes next are developed 

 to a size far surpassing that of the other limbs, and 

 are endowed with proportionate strength. Each of 

 these robust extremities is terminated by a pair of 

 strong pincers (chelce) ; but the two differ in their 

 structure, and are appropriated to Afferent uses. 

 That of one side of the body has the opposed edges 

 \ of its terminal forceps provided with large, blunt 

 tubercles, while the opposite claw is armed with 

 sharp teeth. One claw, in fact, is used as an anchor, 

 by which the lobster holds fast by some submarine 

 fixed object, and thus prevents itself from being 

 tossed about in an agitated sea ; the other is a cutting 

 instrument for tearing and dividing prey. 



