CRUSTACEA PODOPHTHALMIA. 



Order I. EUBRANCHIATA. 



The subdivision of the Eubranchiata or Decapoda into three groups, 

 Brachyura, Anomoura, and Macroura, proposed by Milne Edwards, has 

 been mentioned. This arrangement has been objected to by some 

 authors, who recognise only the first and last groups as natural ; the 

 Anomoura being distributed between the others. On this subject we 

 offer the following considerations. In the course of our observations 

 we shall have to assume the correctness of the subdivisions of the 

 Brachyura, which subject is discussed on the following pages. 



The division Anomoura, was instituted for certain Decapoda having 

 an intermediate character between the Macroura and Brachyura. 

 When these two great groups are regarded in their embryogenic 

 relations, the propriety of recognising such a division seems to be 

 strikingly apparent. We observe, in this light, that the species are 

 like marks along the several lines, between the lower and higher of 

 these grades, some partaking nearly of the character of the higher 

 grade, others nearly of the lower ; yet they are so far distinct, that 

 the relation of the whole is better apprehended, if they are arranged 

 in a separate division — as a kind of transition class — than if the spe- 

 cies are divided, and merged in the two grand divisions. Viewing the 

 Eubranchiata in their relative grades, we naturally look upon the 

 Brachyura as having the higher position — as higher in space, if we 

 conceive the generic names as having a location ; and, the Macroura, 

 in a similar manner as having a lower position ; while between the 



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