272 . MARINE INVERTEBRATES 



thicker than the other two. The abdomen is broad, covering the whole 

 under side of the body, and is marked off with prominent raised ridges 

 diverging from the center line. The legs are all beset with long, rough 

 spines. Habitat, the northwest coast. Taken from the stomachs of fishes 

 off Monterey, California. (Plate LXII.) 



SUBORDER BRACHYUBA 

 THE CRABS 



This group contains the true crabs, which are the highest of 

 the Crustacea. In form they are quite the reverse of the first 

 group. In the Macrura except in the anomalous forms 

 the body is long and cylindrical and the abdomen extended, but 

 in the Brachyura the body is flat and broad and the abdomen 

 short and reflexed. Crabs of this suborder inhabit all seas of the 

 globe, and are found from the shore to great depths. Some spe- 

 cies live on land, some on the shore, some in deep water. Some 

 forms burrow in the sand ; others live under stones and boulders, 

 or conceal themselves in crevices of rocks or in the cavities of 

 sponges. They are divided into many families, and creep, climb, 

 swim, or burrow, their structure being modified to their respec- 

 tive modes of life. There is also great variation in their shapes 

 as well as in their color and markings. This diversity is so great 

 and peculiar that it seems as though each one were more curious 

 than tke others. 



In crabs the cephalothorax is depressed and often broader than 

 long. The abdomen is relatively small and is folded under the 

 thorax, lying in a groove which it fits so perfectly as to be quite 

 hidden from above. The appendages of the abdomen are much 

 reduced in number. The male has two pairs ; the female has four 

 pairs, which it uses for carrying its eggs. The first pair of walk- 

 ing-legs are comparatively large, and end in chelae, or pinching- 

 claws. The other eight legs terminate in simple points, except 

 in the swimming varieties, when the fifth pair is flattened to form 

 fins, or swimming-paddles. The eye-stalks are long and fit into 

 sockets on the carapace. Both pairs of feelers are small. The 

 antennules are frequently folded into small grooves. The exter- 

 nal or third pair of maxillipeds are broad and flat, and cover the 

 mouth-parts like a lid, or operculum. 



