♦5 THE VOYAGE OF H.M.S. CHALLENGER. 



cylindrical filaments; Phyllobranchiata are those that have the plumes formed by a 

 series of foliaceous plates; Abranchiata are those that have no such branchial plumes 

 attached to the pereion. 



As most of the genera that belong to this last division possess branchiae attached to 

 some part or other, the term appears to be misleading. 



The Galatheidse and allied families that author separates from the rest of the Trieho- 

 branchiata, and ranges under the head Anomomorpha, which, except for the exclusion of 

 the Paguridae and the Porcellanidae, neither of which arc trichobranchiate, coincides 

 with the Anomaux of Latreille and the Anomala of De Haan. 



The Penaeidae, through the Stenopidae, are supposed to lead from the trichobranchiate 

 form to the phyllobranchiate. 



Observation on the structure of the branchiae of the Pemmdae, however evolved, 

 demonstrates the character of a plume that belongs to a group in which the development 

 is essentially distinct. Although I think we shall be able to show that the branchiae 

 of the Pengeidea as well as those of the phyllobranchiate division have their origin in 

 the trichobranchiate form, I shall, for the convenience of a general classification, range 

 in a separate division those Crustacea in which the branches of the various plumes divide 

 and subdivide in an aborescent manner ; the more so as those Macrura that possess this 

 kind of structure form a well-marked natural group. 



In this Report I therefore follow Dana in placing the Penaeidea in a separate division, 

 as they do not belong either to the Phyllobranchiata or to the Trichobranchiata. I 

 therefore classify them under the head of Dendrobranchiata, which corresponds closely 

 with the Penaeidea of Dana; while the Squillidse, Mysidae, &c, that is, the Schizopoda 

 originally, and later the Stomapoda of Latreille, Edwards, and De Haan, will lie 

 arranged under the head of Anomobranchiata, which term was first used by Dana, and 

 afterwards by Heller. It has, therefore, priority of date, and is less liable to misconcep- 

 tion than the term Abranchiata. 



The following classification of the Macrura — for much of the arrangement of which 

 I am indebted to the experience of all previous carcinologists, and which is based to a 

 large extent on the development and external evidence of the internal structure — will, 

 I think, be found to approximate the conditions required for a natural classification :— 



Suborder MACRURA. 



Trichobranchiata. Dendrobranchiata. Phyllobranchiata. Anomobranchiata. 



