CRUSTACEA. 



577 



FAMILY II. BIPELTATA. 



Body depressed, membranous, and thin; thorax with 

 twin shields; anterior, very large, oval; posterior one 

 supporting the feet -jaws, and five pairs of transverse 

 and angular feet ; intermediate antennae with two fila- 

 ments. It has but one genus, Phyllosoma. 



ORDER III. LuEMODIPODA. 



Head not distinct from the trunk; the second and 

 third segments, having four vesicular bodies under 

 them; antennae four, multi-articulate; mandibles desti- 

 tute of palpi ; post-abdomen short. 



FAMILY I. OVALIA. 



An oval body with transverse segments ; limbs strong, 

 of medium length; those of the second and third seg- 

 ments imperfect, with a long, cylindrical, blunt ter- 

 mination, each provided with an elongated vesicle at 

 the base. It has but one genus. Cyamus ceti, pi. 23, 

 f. 15. 



FAMILY H.--FILIFORMIA. 



With an elongated, linear body, and narrow longi- 

 tudinal segments; limbs long and slender; last portion 

 of the upper antennae jointed. The genera are, Caprella, 

 Proto, and Leptomera. 



ORDER IV. AMPHIPODA. 



Head separate from the segment, to which the an- 

 terior feet-jaws are attached; post-abdomen provided 

 with branchial and swimming appendages beneath. 

 They are narrow, lengthened, and multi-articulate, 

 transversely striated, or branched; mandibles provided 

 with palpi; some of the feet having vesicles. 



FAMILY I. GAMMARIN^E. 



Body posteriorly furnished with cylindrical or conical 

 Etyliform appendages, or with none in some genera. 

 The genera are Cerapus, Melita, Amphithoe, Dexamine, 

 Gammarus, Pherusa, Orchestia, Talirus, Atylus, Coro- 

 phium, Podocerus, Jassa, Phronima, and Leticot/toe ar- 

 tlculosa, pi. 23, f. 16. 



FAMILY II. UROPTERA. 



Lateral appendages at the posterior extremity of the 

 body, in the form of leaflets, and acting as fins. The 

 genera are Hyperia and Phrosine. 



FAMILY III. DECEMPEDES. 



Animals provided with ten feet only. The genera 

 are Typhis, Anceus, and Praniza. 



FAMILY IV. HETEROPA. 



AVith fourteen feet, in most instances all fitted for 

 swimming on the four last only. The genera are, lone, 

 and Apseude talpas, pi. 23, f. 1 7. 



ORDER V. ISOPODA. 



Having a distinct head; mandibles devoid of palpi; 

 three pairs of jaws, the lower ones appearing like two 

 small feet united at their base, or a lip having two palpi ; 

 body somewhat depressed, divided into from three to 

 seven segments; feet ten or fourteen; tail varying from 

 one to nine segments, with branchials; destitute of 

 shell; eyes granulated; antennas generally four. 



SECTION I. AQUATICA. 



Antennae four, anterior with three or four joints; 

 sometimes without antennae ; lower appendages of post- 

 abdomen usually vesicular, having no openings for the 

 entrance of air. 



FAMILY I. EPICAIUDES. 

 Body much depressed above, and concave below, hav- 



ing neither eyes, antennae, mandibles, nor caudal fin. 

 But one genus, Bopyrus. 



FAMILY II. CYMOTHOADES. 



Eyes and antennae four, sometimes indistinct ; mandi- 

 bles horny; feet fitted for walking and prehension; pos- 

 terior extremity with a fin on each side: post abdomen 

 with four or six segments. The genera are, Cymothoe, 

 Cirolana, Eurydice, Nelocira, Limnoria, Scrolls, and 

 JEga. Marginata, pi. 23, f. 18. 



FAMILY III. SPEUEROMIDES. 



Post- abdomen with three segments, the last with two 

 leaflets. The genera are, Zuzara, Sphseroma, Campe- 

 copea, Naesa, Dynamene, Cymodocea, and Anthura gra- 

 cilis, pi. 23, f. 19. 



FAMILY IV. ASELLOTA. 



Last abdominal segment devoid of swimming afpen- 

 dages. The genera are, Asellus, Janira, and Jiera. 



FAMILY V. IDOTEIDES. 



Branchial appendages situated under the post-abdo- 

 men, covered by the valves of the last segment; four 

 antennae in a transverse line, lateral ones with a fila- 

 mentous termination: post- abdomen of three segments. 

 The genera are, Idotea, and Stenosoma lineare, pi. 23, 

 f. 20. 



SECTION II. TERRESTRIA. 



The two intermediate antennae hardly visible, one or 

 two jointed; post-abdomen of six segments; posterior 

 margin of the last with two or four cleft styles. 



FAMILY VI. ONISCIDES. 



Consisting of the true Oniscae. The genera are, Ligia, 

 Philoscia, Qniscus, Porcellio, and Armadillo Vulyaris, 

 pi. 23, f. 21. 



ORDER VI. LOPHYROPODA. 



Head not distinct from the trunk; eye, or eyes, com- 

 pound and sessile; shell sometimes of two pieces, usually 

 large; no palpi on the mandibles; jaws destitute of 

 branchiae ; feet variable in number, fitted for swimming, 

 simple, or branched, or formed of hairy laminae, organs 

 of respiration supposed to be situated in them. 



FAMILY I. UNIVALVIA. 



Shell in one piece, the most part of the body being 

 uncovered. Cyclops quadricornis, pi. 23. f. 22. 



FAMILY II. OSTRACODA. 



Shell either folded in two, or in the form of two valves 

 united by a hinge, and enveloping the body. The genera 

 are Polyphemus, Daphnia, Lynceus, Ceytherina, and 

 Cypris ornata, pi. 23, f. 23. 



ORDER VII. PHYLLOPODA. 



Head not distinct from the trunk; eyes sessile, smooth, 

 and approximate; antennae very short; shield crusta- 

 ceous, free behind; mandibles two; destitute of palpi; 

 the first pair of feet oar-shaped, the other sixty set in 

 pairs, and fitted for swimming. 



FAMILY I. ASPIDIPHORA. 



Eyes not placed on peduncles. The genera are, Lim- 

 nadia and Apus. 



FAMILY II. CERATOPHTHALMA. 



Having no shell, and the eyes seated on peduncles. 

 The genera are, Artemia and Branchipus staynahs, pi. 

 23, f. 24. 



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