110 SEA-SHORE LIFE 



abundant in Long Island Sound on seaweed-covered bottoms, where 

 it attains its maximum size. The backs of these crabs are covered 

 with hairs, and sea weeds, barnacles, and hydroids often grow upon 

 them. They are used only for bait. 



The Toad Crab, fllyas eoarctafiisj. This is a spider crab but 

 its body is relatively large and the legs slender and weak. It 

 spreads over not more than two and a half inches, and the back and 

 legs are often densely covered with seaweed which the crab affixes to 

 its body. It is abundant in shallow, rocky tide-pools from the Arctic 

 Ocean to New Jersey, but lives also in deep water off the coast, 

 where it crawls over rocky bottoms, and provides food for cod and 

 other fishes. It is the commonest spider crab along the New England 

 coast north of Cape Cod. 



The Horseshoe Crab, (Limulus polyphemas, Fig. 25 J. This 

 common animal lives in shallow water along our coast from Yuca- 

 tan to Maine, and is often called the king crab. It is, however, not 

 a crab but is probably a descendant of the long extinct trilobites, 

 and there is reason to believe also that it is related to the spiders 

 and scorpions. It lives off muddy or sandy shores, and is often seen 

 slowly gliding over the bottom or half buried within the mud. 

 The shell over the head and trunk is crescent -shaped, smooth 

 and dome -like with two valley-like furrows along the sides of 

 the back. The large lateral eyes are easily seen, but if we look 

 more closely we will also see two little median eyes farther for- 

 ward. Altogether the appearance of the head region of the horse- 

 shoe crab is quite similar to that of the trilobites which died out in 

 the age of the coal, although the trilobites probably had no median 

 eyes. The abdomen of the horseshoe crab tapers rapidly back- 

 wards and is composed of six fused segments ending in a long, 

 sharp, movable spine, so that the animal is about one foot broad 

 and two feet long. The females are larger than the males. There 

 are seven pairs of legs. The first six end in nipper-like claws 

 while the seventh gives rise to a whorl of oar-like flaps used m 

 pushing the creature over the bottom. The five pairs of append- 

 ages of the abdomen are leaf-like, and serve as gills and for swim- 

 ming. In late spring and early summer the horseshoe crabs come 

 up in pairs upon the beaches, and deposit their eggs in holes which 

 they scoop out in the sand and leave for the waves to fill. They 



