3 io 



MANUAL OF ZOOLOGY. 



mentary as in Crabs. Further, the abdomen does not ter- 

 minate posteriorly in a caudal fin, as in the Lobster. The 

 development in the Anomura appears invariably to take place 

 through Zoea-forms. 



The entire group of the Anomura must be regarded as an 

 artificial assemblage, composed of modified forms of both the 

 Macrura and the Brachyura. 



The most familiar of the Anomura are the Hermit-crabs 

 (Paguridce). In the common Hermit-crab (Pagurus Bernhar- 

 dus] the abdomen is quite soft, and is merely enclosed in a 

 membrane, so that the animal is compelled to protect itself by 

 adopting the empty shell of some Mollusc, such as the common 

 Whelk, which it changes at will when too small. The Hermit 

 is provided with a terminal caudal sucker, and with two or 



Fig. 159. Brachyura. The Spiny Spider-crab (Maza squinadd). 



three pairs of rudimentary feet developed upon the abdomen, 

 by means of which he retains his position within his borrowed 

 dwelling. The abdominal appendages, however, are mostly 

 unsymmetrical. The carapace is not strong, but the claws are 



