THE CRUSTACEA. Ill 



THE name Crustacea is derived from Crusta, a crust or hard 

 shell. The animals, which are annulose or articulated, with 

 jointed legs, possess a double or complete circulatory system, 

 and respire by means of bronchise, or gills. The external shell, 

 like that of insects, is composed of a dense horny substance 

 called chitine, often strengthened, as in the crab and lobster, 

 by the deposition of carbonate of lime. 



The body, being jointed, possesses considerable freedom of 

 motion. The typical number of rings is twenty-one, but these 

 are often soldered together, as we may observe in the crab, so 

 that their relations are obscured. The animal has the power 

 of casting the shell at intervals, and renewing it as the increased 

 growth of the body requires. Otherwise, from the unyielding 

 nature of the carapace, it could not grow. 



SPECIES OCCURRING AT SOUTHPORT. 



Long-legged Spider Crab (Stenorhynchus Phalangtum). This 

 curious species is sometimes found on the sands near low 

 water mark ; all the specimens we have found have been 

 weakly and damaged, though living. 



Slender Spider Crab (Stenorhynchus lenuirostris). Bears con- 

 siderable resemblance to the preceding, but is more 

 slender in its parts, and has little pubescence on the legs. 

 Less abundant than the former. 



Scorpion Spider Crab (Inachus Dorsettensis). In this species 

 the rostrum is much shorter than in the two preceding, 

 and the hue is much duller. 



Hyas araneus. A specimen was once found near where the 

 Whitworth guns were placed. When the legs were 

 extended it covered a space of four inches and a half 



