METAZOA CRUSTACEA. 359 



Ixa (No. 880) is protected by a sharp pointed spike 

 which extends outward on either side of the cephalo- 

 thorax. The arms are flattened vertically so that the 

 movable jaw of each claw moves up and down instead of 

 horizontally. These organs when at rest are folded over 

 the front of the ventral side of the carapace and have the 

 same knobs and markings, as seen in No. 870. 



Maia squinado Latr. (No. 88 1), has a spiny and hairy 

 cephalothorax that is pointed in front and extremely nar 

 row behind where it passes into the flat and spineless but 

 hairy abdomen. The arms in Maia are surprisingly 

 small and weak, while the claws are almost wholly free 

 from spikes and hairs, although the walking-legs are all 

 hairy. According to Leach, Maia is extremely- common 

 in deep water and is called by the fishermen the thorn- 

 back. This same author states that the young often 

 approach the shore. 



Belonging to the same family of spider crabs as Maia 

 is Hyas araneus Leach (No. 882) , which has a carapace 

 without spines and the four pairs of walking-legs well 

 developed. 



The reduction of the walking-legs is carried still further 

 in Lambrus (No. #83). Although most of these organs 

 are wanting in the specimen, yet enough of one leg is left 

 on the right side to show how short, small, and smooth 

 they have become. The arms, on the other hand, are 

 more than three times the breadth of the cephalothorax. 

 and are provided with spines from one end to the other, 



Another peculiarly modified form is Cryptopodia forni- 

 cata M. Edw. (No. 884), in which nothing but the cara- 

 pace, arms, and small, partly hidden eyes are to be seen 

 in a dorsal view. The walking-legs are wholly concealed 

 by the carapace that is greatly extended laterally. The 

 eyes are protected by the flattened rostrum which has a 

 row of tiny dots along its edge. 



The fiddler crab, Gclasimus vocator Martens (No. 885), 

 is a small crab with a quadrangular cephalothorax and in 



