DECAPODA 



373 



Homarus, the lobster, differs from Nephrops in size, form of 

 chelae, etc. 



Palinurus, the crawfish or spiny lobster, one of the Palinura, differs 

 from the crayfishes and lobsters in having a small spine in place of 

 the rostrum, no antennal scale (exopodite), and no chela on any leg. 



Eupagurus (Fig. 278), the hermit crab, one of the Anomura, 

 lives in the empty shells of gastropod molluscs. It has a large, soft 

 abdomen, containing the liver and gonads, twisted to fit into the 

 shell, and without appendages on the right side, save for the uropods, 



Fig. 278. Eupagurus hernhardus, ^. ah. 2, third abdominal limb; tel. telson; 

 th.%, last thoracic limb: sc. scale of antenna. 



of which both pairs are present, roughened, and serve to hold on the 

 shell. The first three pairs of legs are as in a crab, the last two small 

 and chelate. 



Birgiis, the robber crab, is a hermit crab which has grown too 

 large to use the shells of molluscs, and has accordingly re-developed 

 abdominal terga. It lives on land in the Indopacific region, and is 

 adapted to aerial respiration by the presence of vascular tufts on 

 the lining of the gill chambers. Its Zoaeae are marine. 



Lithodes, the stone crab (Fig. 279 j, is by origin a hermit crab. 



