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, ( Tyas coarctatus). 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 polyphemus, Fig. 25). 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 in 
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 
