ANNULOSA: CRUSTACEA. 



231 



development in the Anomura appears invariably to take place 

 through Zoea/-forms. . 

 ■ The most familiar of the Anomura are the Hermit-crabs 

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

 dus)\h& 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 

 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 



Fig. 75. — Brachyura. The Spiny Spider-Crab (.^a/a f^/rtwrtrfip). 



ivell developed, one being always larger than the either. Other 

 forms of the Anomura are the Sponge-crabs {Dromia), the 

 Grab-ldbsters (Forcellance), and the Tree-crabs (Btrgus). 

 : Tribe C. BiUChyura. — The " short-tailed " Decapods, or 

 Crabs, are distinguished from the two preceding tribes by the 



