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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 embryological 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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