DESCRIPTION OF GENERA AND SPECIES. 



Class CRUSTACEA. 



Subclass MALACOSTRACA. 

 Thoracipoda, H. Woodward. 



Order EDEIOPHTHALMA, Leach, 1815. 



TetradecajJodes, do Blainville, 1816. 

 Arthr'ostraca, Burmeister, 1837. 

 Choristopoda, Dana, 1846. 



Suborder AMPHIPODA, Latreille, 1816.' 

 Tribe I. AMPHIPODA GAMMARINA. 



Head not coalesced with the first segment of the perseon. 



Perason of seven distinct segments, very rarely reduced to six {Dulichia) by the 

 coalescence of the last two. 



Pleon of six distinct segments bearing ajDpendages, and the telson ; rarely with two 

 (Atylus), or with three (Goplana), of the segments coalesced, or with only five distinct 

 segments and five pairs of appendages (Dulichidse); the telson (probably) never absent.^ 



Eyes generally two, sometimes four (Ampelisca) or none {Byhlis ahyssi, Sars, &e.), 

 seldom very large or projecting much above the surface of the head ; generally with many 

 component ocelli, sometimes simple (Ampeliscidse). 



Antenna, two pairs ; the proportions not constant ; the upper often having a 

 secondary flagellum, well-developed or rudimentary, but very rarely [Gammarus 

 sarmatus, Dybowsky) of great length. 



Maxillipeds generally with two pairs of plates, neither pair coalesced, and a four- 

 jointed palp ; the palp rarely with only three joints {Normania), or only two {Lafystius). 



' For definitions, see Glossary, and Notes on Latreille, 1816 (p. 95), 1817 (p. 95), 1829 (p. 137) ; Burmeister, 1837 

 (p. 170) ; Milne-Edwards, 1840 (p. 184); Dana, 1852 (p. 256); Claus, 1880 (p. 508), 1884 (p. 553) ; Gerstaecker, 1886 

 (p. 579). 



2 But see, in Bibliograph)-, Notes on Icridium, Grube, 1864 (p. 348), Ichthyomyzocus, Hesse, 1873 (p. 417, and in 

 Appendix), the Orchestidie, Zaddacli, 18"(8 (p. 485). 



(ZOOL. CHALL. EXP. — PART LXVII. — 1887.) XxX 7G 



