OUR CARCINOLOGICAL FRIENDS. 101 



six pairs of legs. The food, which consists of va- 

 rious small animals, largely worms, is conveyed to 

 the mouth by one or more of the foot-pincers, where 

 it is closely rasped and triturated by the rubbing 

 together of the spiny basal joints of the legs. 



The horseshoe crab {Limulus polyphemus) prefers 

 for its habitat the protected bays and estuarine 

 waters, where it burrows in the sand or mud just 

 sufficiently to cover its body. In this operation of 

 burrowing the head is the excavating organ, while 

 the feet and tail, firmly pressed backward, are the 

 force. When placed on its back the animal has 

 some difficulty in at first righting itself, but by 

 arching upward the carapace, at the same time re- 

 ceiving assistance from the tail, it soon recovers 

 itself. 



The horseshoe crab so closely resembles in ap- 

 pearance and structure the ancient trilobites, whose 

 remains are so numerously buried in the older rock- 

 deposits of our earth, that there are strong grounds 

 for concluding that the latter were the true pro- 

 genitors of the modern race, a conclusion that has 

 been strongly reinforced by the embryologi .al study 

 of the two types. The young Limulus, in fact, so 

 nearly resembles the young of certain forms of 

 trilobites as to be barely distinguished from them ; 

 at this period the spine is still wanting. Subse- 

 quent moulting of the carapace is preceded by a 

 splitting of the latter along its border, the animal 

 drawing itself through the opening thus made. 



This species is found abundantly along the coast 

 from Maine to Florida. Where left exposed on 



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