THE CRAYFISH 



141 



their legs are very long and slender.^ These crabs frequent 

 oyster-ljeds and sea-l.)ottonis in general. When seen stalking 

 over such uneven surfaces, the advantage of these stilt-like 

 legs is at once evident. The surface of the bodj' of some 

 species of spider-craljs is hairy, entangling inorganic matter, 

 while hydroids, barnacles, and algae attach themselves to the 

 shell, so that the crab, when quiet, is concealed by them, while 

















.- »«-<«M 



Fig. 136. — The smaller spider-crab, LiMnia dubia. Two specimens lying on 



the beach. 



these attached organisms, in turn, gain bj' their association 

 with the crab most of the advantages of locomotion. Libin'ia 

 du'bia (Fig. ISC)), which ranges from Cape Cod to the Gulf 

 of Mexico, is the commonest of our species that undergo such 

 concealment. The great Japanese spider-crab is said to be 

 the largest of all the Crustacea, some individuals measuring, 

 from tip to tip of the first pair of legs, 18 to 20 feet. 



The edible crab is a tj^pical arched crab. It is so called 



iFig. 136. 



