300 On the Classification of the Crustacea Choristopoda. 
Subtribus IL. ArcrunrpsE, vel Axwrsoropna IporxrcA.— Appendices duse. postice 
abdominales lamellatze et bene opereuliformes, appendices branchiales tegentes. 
Subtribus IIL "TAxArpEA, vel Awisoropa ONrscrcA.— A. ppendices duze postiez ab- 
dominales plus minusve styliformes, subterminales, interdum obsoletze. 
Tribe 3. Amphipoda.—Tlhe Amphipoda contain two prominent di- 
visions, distinguished by the organs of the mouth, the eyes and general 
habit, the Gammarus and Hyperia sections, as laid down by Edwards. 
The addition of the Leemipoda to the Amphipoda iced a third 
division. "Phe sections are hence :— 
Subtribus L. CaenELLIDEA.—Maxillipedes elongati, palpiformes. Caput oculique 
mediocres Abdomen obsolescens. 
Subtribus Il. GAwwaRrpDEA.—Maxillipedes elongati, palpiformes. Caput oculique 
mediocres. Abdomen appendicibus sex natatoriis sexque styliformibus instructum. 
Subtribus IIL. HyrrgrpzA.—Maxilipedes abbreviati, lamellati, opereuliformes. 
Oaput grande, oculorum corneis plerumque tectum. Appendices abdominales ac in 
Gammnarideis, Yatius lamellatze. 
The Caprellidea have the habit of certain of the Anisopoda, and 
their short abdomen calls to mind the Isopoda. "They therefore prop- 
erly stand first among the Amphipoda. 'The Caprellids like the species 
of Arcturus and 'l'anais, cling and stand upon seaweeds, etc., by their 
six hinder legs, while the body and the other legs are extended, for . 
the purpose of capturing their food and conveying it to the mouth. 
In the following synopsis of the Families, Subfamilies and Genera, 
some new genera are included, discovered by the author in the course 
of the cruise of the Exploring Expedition under Capt. Wilkes. 
TRIBUS I 
ISOPOD A. 
SubtrbusI. IDOTZEIDEA.* 
Fam. I. IDOTZEIDZE. 
Pedes fere consimiles, plus minusve ambulatorii. 
G. 1. Iporza, F'abr.— Antenna externe longiores, flagello multiartieulato confectze, 
(2. EporrA, G'uerin.— Antenne externz internis parce longiores, flagello pauci- 
articulato confectz, basi paulo longiore quam basis internarum. 
G. 3. Emicusowra, Dana.— Antenne externe internis multo longiores, geniculatze, 
6- articulatz, flagello carentes. Pedes subsequi consimiles. 
G. 4. Orzawnss, Dana.—Antenne externe multo longiores, 5—-6- articulatz, non 
geniculatz, flagello carentes. Pedes 4ti 3tiis valde breviores, et 4ti 5ti 66i 'Imi 
longitudine sensim inerescentes. JAbdominis opercula laminam appendiculatam 
ad artieulationem gerentia. De: 
G. 5. ErrzLxs, Dana.—Antennce breves, longitudine subsque; externe flagello 
carentes, non geniculate. Pedes subzqui. FO 
Fam. 2.  CHZETILIDJE. 
Pedes 6ti longissimi, setiformes et multi-artieulati. 
G.1. Cuzrmi, Dano.--AÀntennse lm longiores, superiores, 2d flagello ue 
artienlato confect». Pedes Imi breves, non unguiculati. A bdominis Ko 
laminam appendiculatam ad artieulationera gerentia, 
* "The genera Jrichsonia, Cleantis, Epel; ys and Chotilia, axe described. by the 
author in this Journal, [2,] viii, 424, 1849. 
