62 THE LIFE OF CRUSTACEA 



Crab, Lithodes maia (Plate VIII.) belongs — seem at 

 first sight to have little resemblance to the Hermit 

 Crabs, for they have the abdomen very small, and 

 tucked up under the body as in the true Crabs. 

 Like the Porcellanidse, mentioned above, however, 

 the Lithodidae have only three pairs of walking legs 

 behind the chelipeds, the last pair being feeble and 

 usually folded out of sight within the gill chambers. 

 The relationship of the Lithodidae to the Hermit 

 Crabs is shown by the abdomen, which is more or 

 less twisted to one side, and has swimmerets only on 

 one side in the female, and quite wanting in the male. 



The Hippidea are curious little Crabs found burrow- 

 ing in sandy beaches in the warmer seas. They 

 have the abdomen tucked under the body, and the 

 legs flattened for shovelling the sand. 



The Brachyura, or true Crabs, form the fourth 

 section of the Reptantia, and are distinguished by 

 having the abdomen reduced to a tail-flap, which is 

 doubled up under the cephalothorax, and is usually 

 without any trace of the uropods which are present 

 in all the groups already mentioned, with the single 

 exception of the Lithodidae. At the sides of the 

 head the side-plates of the carapace become firmly 

 soldered to the *'epistome," a plate which lies in 

 front of the mouth, and in this way there is formed 

 the " mouth-frame," within which lie the jaws, 

 covered in by a pair of " folding-doors " formed by 

 the flattened third maxillipeds. 



