BRACHYURA. gg 



liarities in the sternal plate and abdomen, which are of considerable 

 weight. While, in a large part of the species, the male abdomen is as 

 broad behind as the sternum, there are others in which it is much nar- 

 rower behind. The sternum may be narrow behind, with an abdomen 

 equally narrow at base — broad with an abdomen narrow at base — 

 broad with an abdomen broad at base; and these differences are of 

 much use in certain divisions of the species. 



From this review of the relative value of the distinctions among 

 the Brachyura, we may pass to the use of these differences in classifi- 

 cation. And, in the first place, we would express our high estimate 

 of the vast labour and profound researches in this department, of 

 Edwards, the eminent Zoologist of France, and first Crustaceologist 

 of the age. And if we venture to differ from him in any point, it is 

 with the consciousness of having been helped forward to our starting- 

 point by the results of his investigations. And as science with the 

 world, and least of all with him, is not at a stand-still, we may believe 

 that his own labours, if recently bestowed on the subject, would have 

 evolved many improvements, the long period of near twenty years 

 having elapsed since his system was published. 



We cannot omit to mention, also, the benefit derived from the 

 magnificent work of De Haan. We have admired the wonderful 

 fidelity of his plates, the thorough spirit of investigation displayed 

 throughout his princely volume, and the judgment with which he has 

 seized upon typical forms in instituting genera. We have observed 

 the large addition of facts developed by his investigations, and the 

 new light thrown upon the relations of many groups. Yet we shall 

 have to object to a defective system of arrangement and description, 

 especially as relates to the Brachyura, by which his types are often 

 thrown into wrong associations, and the groups they typify are laid 

 down with false limits. 



Among the distinctions pointed out in the foregoing review, we 

 place first those dependent on the branchial system. The characters 

 based on the opening of the efferent channel are fundamental in them- 

 selves, and the species of the two groups thus indicated, have wider 

 differences than any that may be found among the species in either 

 group. The Leucosoidea are thus strikingly distinct from all other 

 Brachyura. 



But we exclude from this division, as done by De Haan, the Cory*- 

 toid species, placed in the group by Edwards ; for these are Cancroid 



17 



