REPORT ON THE CRUSTACEA MACRURA. :i 



In the following table (pp. 4, 5) 1 have brought together, in one general scheme, 

 an outline of the several classifications that have been adopted by the more distinguished 

 carcinologists, so fax as they relate to the Macrurous Crustacea. 



It is interesting to observe how closely these different systems correspond as to their 

 general conclusions, the chief points of distinction being with regard to those genera 

 which, while they resemble one group in external form, approach some other group in 

 some important structural character. 



The arrangement of Latreille agrees closely with that of De Haan, even to the intro- 

 duction of the phyllobranchiate families of the Paguridas and Porcellanidae among the 

 anomurous forms. 



The classification of Milne-Edwards differs in separating the Eryonidae, Scyllaridse, 

 and Palinuridae from the Astacidea, where all other authors, excepting Heller, place them, 

 and in grouping them along with the Galatheidae. 



Dana differs from the others in the exclusion of the Galatheidae and allied families 

 from the Macrura altogether, and in forming a sub-tribe to receive Poiasus and its allied 

 genera, among which he includes Stenopus. 



The more recent system proposed by Professor Huxley is almost identical with that 

 of Latreille, as given in Cuvier's Regne Animal, 2nd ed., vol. iv., 1829, and quoted by 

 Milne-Edwards in his Hist, des Crust., t. i. p. 217, differing only in the removal of 

 the family of the Penseidae from among the Salicoques, where all preceding authors, 

 excepting Dana, have placed it, and transferring the same to range with the Tricho- 

 branchiata, a section that corresponds with that of the " Homards " of Latreille, and is 

 synonymous with the three divisions — Astaciens, Thalassiniens, and Cuirasses of 

 Milne-Edwards — and with the Astacina of De Haan. It, moreover, corresponds with 

 the Astacidea, Thalassinidea, and Penseidea of Dana, and with the Loricata, Astacidea, 

 and Thalassinidae of Heller, whose classification is identical with that of Milne-Edwards, 

 excepting in the terms selected for the names of the separate groups. 



It would thus appear that the various systems of classification have failed to receive 

 acceptance by each successive naturalist, from the circumstance that the several tribes 

 or groups have received their distinguishing title from the most prominent or dis- 

 tinctive animal in its respective group or tribe, a circumstance that must render a 

 nomenclature very liable to be changed with any variation of individual thought, 

 dependent upon the opportunity of study, as well as with the increase of knowledge 

 through extension of research. 



The nomenclature recently suggested by Professor Huxley, being based upon the 

 structural character of the branchiae, appears not to be open to this defect. 



He has proposed that the Macrura be divided into three groups, — the Trichobranchiata, 

 the Phyllobranchiata, and the Abranchiata. 



Trichobi'anchiata are those that have the branchial plumes made up of long 



