148 



NATURAL HISTORY. 



mass of a sponge. One species occurring in the Eastern seas always bears 

 a larsre sea-anemone on its back. Doubtless this association of forms works 

 to the advantage of all concerned, — sea-anemone, sponge, or hydroids 

 tend to conceal the crab from its many enemies, while at the same time 

 they obtain many a good meal from the crumbs dropped from the crab's 

 dinner. A somewhat similar condition occurs in the genus Hypoconclia, 

 the two species of which inhabit the seas of tropical America. Their 

 backs are not hardened ; but are soft like the abdomen of the hermit-crab, 

 and hence need protection. This is effected by hiding the body beneath a 

 shell (hypo-concha) of some bivalve mollusc, and this shell is borne about 

 wherever the crab may wander. In the true hermit-crabs the coiled abdo- 

 men and its calcareous plates are well adapted to take a firm hold of the 

 shell which protects their weak point, and in Hypoconcha there are means 

 for holding the protective valve in place. The hinder part of the body i3 

 shaped to fit in the angle beneath the hinge of the shell, while two pairs 

 of feet are bent upwards and hold the shell down in much the same way 

 that a man holds his hat on his head in a high wind. 



The spider-crabs receive their common 

 name from their spider-like appearance. 

 The body is comparatively small, while 

 in most cases the legs are long and slen- 

 der, frequently far exceeding those shown 

 in our cut. Of the spider-crabs there is an 

 immense series, almost all of them being 

 inhabitants of the warmer seas. One of 

 them (Macrocheira) we have already 

 referred to as the largest of all crusta- 

 ceans. It occurs in the seas surround- 

 ing the islands of Japan, and seems to 

 be somewhat rare. 



Most common along our Northern 

 Atlantic and Pacific coasts are the species 



Fig. 131.— Spider-crab (Inachodes hemphilli) r,f ,.^r.l- n ^k, „„/] 1 1 / n \ 



of the Pacific coast. ot iock-crabs and shore-crabs ( Cancer) f 



large, heavy forms which possess but 

 little to interest any except the professional student except in edible qual- 

 ities ■ but in this point they excel, as is well recognized on the Pacific 

 coast, while on the shores of the Atlantic they are largely neglected, a fact 

 which may be due to the abundance of other edible forms. Among these 

 others may be mentioned the celebrated 'soft-shelled crabs' so highly 

 esteemed by epicures. These are merely specimens of a species of swim- 

 ming-crab (Neptunm) taken immediately after the molting, and while the 



