284 MARINE INVERTEBRATES 



FAMILY MAIIDJE 



The members of this family are known as " spider-crabs." 

 Their bodies are thick and more or less round in form, narrowing 

 in front to along, beak-like projection. The surface is generally 

 rough and irregular, having tubercles, spines, prickles, and hairs. 

 The legs are long. These crabs are often covered with seaweeds, 

 hydroids, and other organisms, which they gather with their long 

 and flexible chelipeds and place upon their backs, presumably to 

 conceal themselves from their enemies. They seem to select, 

 instinctively or with reason, such tilings as will bear transplant- 

 ing, sometimes using sponges and polyps which are not destroyed 

 by being torn apart, and they also select their dress with refer- 

 ence to its masking uses. A Hyas covered with bright-colored 

 algae was seen to remove them and replace them with sponges, 

 when transferred to the locality of the latter, where the 

 former did not grow. The animal takes in his claw the object 

 he has gathered, and first holds it to his mouth, where it is 

 moistened with a secretion of mucus or cement, and then places 

 it on his back. If it does not hold, the operation is repeated, 

 often several times, a new spot on the shell being selected each 

 time. It has also been found that the coats of these crabs are 

 covered with hairs which are differently arranged in different 

 genera, some being hooked, others serrated, etc., and that 

 these aid in holding the transplanted organisms in place. The 

 crab is sometimes so covered with these growths as to be entirely 

 concealed beneath them. It is a sluggish animal, and inhabits 

 shallow water along the whole of the Atlantic and Pacific coasts 



GENUS Libinia, 



L. dubia, L. emarginata. These two species inhabit the Atlantic 

 coast, and are found on muddy shores and flats, among decaying sea- 

 weed, in eel-grass, and even beneath the surface of the mud. They are 

 covered with hairs, and sometimes have planted on their backs algae, hy- 

 droids, and even barnacles. The legs of L. emarginata often spread a foot 

 or more. The males are much larger than the females. The species ranges 

 from Maine to Florida. L. dubia does not extend north of Cape Cod. 

 It is found more commonly than L. emarginata in very shallow water 



