MALACOSTRACA 



309 



Sub-order Macrura. Abdomen long. Homarus (lobster) ; Neph- 

 rops (Norway lobster, sea crayfish); Astactis (fresh-water crayfish); 

 Palimirus (rock lobster), whose larva was long known as the glass- 

 crab (Phyllosoma) ; Pen^us^ a shrimp which passes through Nauplius, 

 Zoaea, and Mysis stages ; Lztctfer and Sergestes are also hatched at a 

 stage antecedent to the Zoaea ; Crangon vtdgaris (the British shrimp) ; 

 Palawan^ Pandalus, Hippolyte (prawns) ; Galathea (with the abdomen 



abd 



FIG. 163. Hermit-crab withdrawn from its shell. 



The anterior appendages are broken off. 



hd., Head; th., thorax ; abd. t abdomen. 



bent forwards) ; Pagurus> Eupagurus (hermit-crabs) ; Birgus latro (the 

 terrestrial robber or palm-crab), in which the upper part of the gill- 

 cavity is shut off to form a "lung," the walls having numerous 

 vascular plaits. 



Sub-order Brachyura. Abdomen short, and bent under the 

 thorax. It is narrow in the male, and does not usually bear more 

 than two pairs of appendages ; it is broader in the female, and 

 bears four paired appendages. The ventral ganglia have fused 



