256 THE VOYAGE OF H.M.S. CHALLENGER. 



1852. Dana, James DwicxHt. 



On the Classification of the Crustacea Choristopoda or Tetradecapocla. The 

 American Journal of Science and Arts. Second Series. Vol. XIV. November, 

 1852. New Haven. Number XLI. Appendix, pp. 297-316. 



" The term Choristopoda, applied to the Tetradecapoda, alludes to the subdivision of the thorax 

 into segments, each devoted to a separate pair of legs ; this is a prominent peculiarity of tlie 

 species, distinguishing them from all the Podophthalmia, and with rare exceptions from the 

 Eutomostraca." 



" The Amphipoda are uniformly characterized by having — 



"1. The three posterior pairs of thoracic legs thrown backward and more or less obliquely 

 forward, and constituting one series, while the four anterior pairs are thrown forward and 

 outward, in another series ; this arrangement may be represented by the figures 4 : 3, 

 (or 2 + 2 : 3, as the four pairs of the first series are often in two sets of two pairs each). 



" 2. The branchial appendages thoracic. 



" 3. The abdominal members in two sets, the three anterior pairs subnatatory, the three 

 posterior styliform — an arrangement represented by the figures 3:3." 



From these he distinguishes the Isopoda, and places Arcturus, Tanais, &c., in an intermediate 

 group or tribe called Anisopoda. 



" The Amphipoda contain two prominent divisions, distinguished by the organs of the mouth, 

 the eyes and general habit, the Gammarus and Hyperia sections, as laid down bj' Edwards. 

 The addition of the La?mipoda to the Amphipoda introduces a third division. The sections 

 are hence : — 



" Subtribus I. CAPRELLiDEA.^Maxillipedes elongati, palpiformes. Caput oculique mediocres. 

 Abdomen obsolescens. 



"Subtribus IL Gammaridea. — Maxillipedes elongati, palpiformes. Caput oculique mediocres. 

 Abdomen appendicibus sex natatoriis sexque styliformibus instructum. 



" Subtribus IH. Hyperidea. — Maxillipedes abbreviati, lameUati, operculiformes. Caput grande, 

 oculorum corneis plerumque tectum. Appendices abdominales ac in Gammarideis, latins 

 lamellatae. 



"The Caprellidea have the habit of certain of the Anisopoda, and their short abdomen calls to 

 mind the Isopoda. They therefore properly stand first among the Amphipoda." 



The first subtribe, Caprellidea, contains : — Fam. 1. Caprellida;, with the genera, 1. Prota, 

 Leach; 2. Profella, Dana. "Mandibitlae palpigerje. Branchiffi segmentis 3tio itoque 

 affixae. Pedes 3tii 4tique obsoleti articulo Imo styliformi excepto. ; " 3. Caprella, Lamk.} 

 4. JEgina, Krdyer ; 5. Cercops, Kroyer ; 6. PofJalirius, Krciyer. Fam. 2. Cyamidfe, 

 with one genus Cymimn. 



On subtribe IT. Gammaridea, he remarks : — " [Among the Gammaridea, the author finds that 

 the posterior caudal stylets offer important characters for distinguishing natural groups or 

 genera, and uj)on this ground, some new genera have been recognized among the Corophida; 

 and Gammaridse, and others that have been rejected are sustained. Thus Ipliimedia is 

 distinct from Amphithoe, Mxra and Dercothoe from Gmnmanis, etc.]." He then gives 

 Fam. 1. DulichidiB. G. 1. Dulichia, Kroyer. Fam. II. Cheluridw. G. 1. Chelura, 

 Philippi. Fam. III. Corophidae. Subfam. 1. Clydoninoe. — " Styli caudales sex simplice.s, 

 subulati." Chjdonia, Dana, Amer. J. Sci. [2], viii, 140. 



"Subfam. 2. Corophina?. Antenna3 plus minusve pediformes. Styli caudales Imi 2dique 

 biramei. A. Digitus nullus 2-articulatus. 1. Styli caudaleg Stii miiiuti, simplices, 2di 

 Imique ranw externa adtriformi." G. 1. CoropMum, Latr.; G. 2. Siplionacetes, Kroyer. 

 " 2. Styli raudaJeK Stii nmiufi, dx exserti, dmpliees, 2di Imiqiie ramis extus nnn pirxcipue 



