94 CRUSTACEA. 



rax, beneath which it is folded in repose, and not furnished 

 with a terminal fan-like tail. The common crab is an example 

 of this sub-order. 



2. Macroura, having the abdomen longer than the thorax, 

 beneath which it is not closely folded when at rest, and fur- 

 nished with a fan-like tail. The lobster, prawn, and shrimp, 

 are examples of this sub-order. 



M. Milne Edwards, one of the most celebrated of modern 

 crustaceologists, in a valuable work published at Paris, in 

 1834, has proposed the establishment of another or third 

 division, under the name of Anomoures, forming a passage 

 between the two other groups, and composed of various spe- 

 cies which appear to belong to neither, and which, if intro- 

 duced amongst them, would violate the spirit of all natural 

 arrangement. 



In the various animals which compose the sub-order 

 Brachyura, the shell or carapax which covers their bodies 

 also conceals the greatest portion of the abdomen, and is in 

 general of a square, oval, or rounded form, its transverse 

 diameter exceeding,or at least equalling, its length, its upper 

 surface exhibiting various areas divided by impressions, which 

 correspond for the most part with the insertion of the muscles 

 within the shell, and which form so many regions corre- 

 sponding with the internal organs immediately beneath the 

 different areas. The front of this shell bears a pair of eyes 

 placed on footstalks (marked c in the figure), and two pairs 

 of antennae (a, b), and beneath these is perceived a pair 

 of large, flat, and articulated pieces {d), which, when raised, 

 are found to conceal a very complex apparatus, composing 

 the mouth, and consisting of an upper lip and tongue, a 

 pair of horny mandibles bearing a jointed palpus, a pair of 

 internal* and external maxilla:, and three pairs of foot jaws 



* By some accident M. Edwards has described the internal maxillae as 

 the anterior foot jaws, p. 255. 



