552 



CRUSTACEA. 



sometimes with a claw; the other six feet with their last 

 joint fin-*hupeil. 



The genera are. Album-*, Hippa, and 



Kemiptt letludinariut, p>. 3U, f. 7. Lateral and middle an. 

 tenure short, bent, and nearly equal ; exterior fe*t-jawa arm. 

 -li;t|ied, ti-niiinat.-d by a hook , first pair of feet eudingiii point- 

 ed plates, the real with ciliated pointed fins. 



FAMILY II. PAGURII. 



Shell but slightly crusUceous ; two anterior feet didactyle ; 

 next four pain with long acute tarsi ; last four pairs smaller, 

 irrmiiiHting with a forceps ; nometimes u-ith a pointed hook. 



'I In- t-enera are, Hirffiis, and 



Pagunu laticauda, pi. 30, f. 8. Oblong ; tail, long, naked, 

 and rarely divided into segments; anterior feet with forceps, 

 mid unequal ; last four pairs very s.uall ; exteriur antennae 

 long ; interior, short, approximate. 



FAMILY III. PAI.IM-RINI. 



Terminated by a fan-shaped post-abdomen, produced by the 

 lateral appendage* of the last and preceding segments. 



There is but one genus : 



Paiinurut locutta, pi. 3n, f. 9. Outer antennae, very long, 

 spiued, or hairy ; two middle ones, shorter and bifid ; exterior 

 feet-jaws, formed like feet ; feet, middling lung, with short 

 claws : shell, somewhat cylindrical, and spiny ; abdomen, six- 

 jointed, elongated, with a termination consisting of five laminae, 

 tan-shaped ; eyes seated on peduncles. 



FAMILY IV. SYLLARIDES. 

 Having the peduncle formed like a depressed crest 

 The genera are, Thenus and Scyllarus. 



FAMILY V. GALATHIN.& 



Feet all alike, but the two anterior, which are didactyle. 

 The genera are, Eryon, Magalopa, Galathea. 

 PorceUana platychelet, pL 30, f. 10. Lateral antennae long, 

 setaceous, placed on the exterior side of the eyes: interme- 

 diate ones lit roove3 ; body, orbicular, somewhat depressed ; 

 tail, with a ciliated marL'in, and bent below ; ten feet, posterior 

 two small, anterior didactyle. 



FAMILY VI. ASTACIN*. 



Four or six of the anterior feet didactyle ; terminating abdo- 

 minal exterior leaflets, entire in some, and in others divided by 

 a suture. 



The genera are, Thala&sina, Gebia, Axius, Callianassa, Ne- 

 phrops, and 



Ait ana Marinut, pi. 30, f. 11. Antennae four, unequal, mid- 

 dle ones shortest ; peduncle, with scale-shaped teeth ; exterior 

 feet-jaws long, two first joints with stiff hairs ; body, oblong, 

 sub-cylindrical, with a projecting beak in front ; terminating 

 nix fan-shaped ; six anterior legs didactyle, first, long and 

 thick ; forceps, tuberculated and apined. 



FAMILY VII. CARIDES. 



Intermediate antennae placed above the lateral ones, pro- 

 truding with two or three filamentary terminations. 



The genera are, Penaeus, Stenopus, Alpbeus, Hippolyte, 

 Autonnmea, Gnathopbyllum, Hymenocera, Nika, Athanas, 

 Atya, Egeon. Crangon, Pandalus, Pasiphaea, and 



Paltemon Serratut, pi. 30, f. 12. Intermediate antennae con 

 listing of three filaments, one short and thick, two long and 

 setaceous; lateral ones longer than the body; four anterior 

 legs didactyle ; anterior, smaller than the second pair ; last 

 joint of exterior feet jaws shorter than the preceding; shell, 

 thin, elongated, cylindrical, with two sharp points before ; ros- 

 trum, long and serrated. 



FAMILY VIIL SCHIZOFUDA. 



Feet slender, filiform, fitted for swimming only ; none of 

 them hand-shaped, but having either a long, lateral appendage, 

 or deeply cleft, or multifid at their extremity. 



The genera are, Mysis, Zoea, and 



Nebalia Herbttii, pi. 30 , f. 13. Thorax having a movable 

 rostrum anteriorly ; anterior pair of legs simple and longest, 

 the rest approximate and simple ; the last joint cleft ; anten- 

 nae two, placed above the eyes, the last joint bifid and multi-ar- 

 ticulate. 



ORDER II. STOMAPODA. 



The branchiae suspended, in the form of tufts, on the lower 

 appendages of the post-abdomen ; head, distinct from the trunk, 

 urge, and separated into two parts ; shell, membranaceous ; in- 

 termediate antennae with two or three filaments at their termi- 

 nations ; six posterior feet filiform ; body terminated by a folia, 

 ceo us fin. 



FAMILY L U.NIPBLTATA. 



With an elongated and narrow body ; eyes and intermediate 

 antennas placed on an anterior elongation of the thorax ; ex- 

 terior feet-jaws, and four anterior limb?, terminated by a mono- 

 dactyle forceps ; the other six limbs fitted for swimming, with 

 the last joint brush-shaped ; lateral antennae having a scale at 

 the base ; intermediate ones trifilamentary. 



The genera are, SquiUa, Erichthus, and 



A'.ima hyalina, pi. 30 , f. 14. ' Shield and body much elongated ; 

 intermediate antennae seated on a very long three-jointed pe- 

 duncle, terminated by three filaments ; eyes, very large ; shell, 

 broade.-t behind ; first segment destitute of feet ; the next three 

 with very small limbs ; the five next segments provided with a 

 pair of oval plates. 



FAMILY II. BIPKI/IATA. 



Body, depressed, membranous, and thin ; tin. rax with twtu 

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

 the feet-jaws, and five pairs of transverse and angular feet ; 

 intermediate antennae with two filaments. 



It has but one genus, Phyllosoma, 



ORDER III. LJEMODIPODA. 



Head not distinct from the trunk ; the second and third seg- 

 ments, having four vesicular bodies under them ; antenna? four, 

 multi-articulate ; mandibles destitute 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 segments tm. 

 perfect, with a long, cylindrical, blunt termination, each pro- 

 vided with au elongated vesicle at the base. It has but one 

 genus. 



Cyamus ceti, pi. 30, f. 15. With a small, conical, truncated 

 head ; body, orbiculai depressed ; having ten segments ; eyea 

 compound; lateral antennae four, jointed and setaceous ; feet 

 eight, unguiculated, second and third segments with two pairs 

 of spurious ones, to which are attached the branchial vesicles. 



FAMILY II. FILIFORMIA. 



With an elongated, linear body, and narrow longitudinal seg- 

 ments ; limbs long and slender ; last portion of the upper an- 

 tennae jointed. 



The genera are Caprella, Proto, and Leptomera. 



ORDER IV. AMPHIPODA. 



Head separate from the segment, to which the anterior feet- 

 jaws are attached ; post.abdomen provided with branchial and 

 swimming appendages beneath. They are narrow, lengthened, 

 and multi-articulate, transversely striated, or branched ; man 

 dibles provided with palpi ; some of the feet having vesicles. 



FAMILY I. GAMMAKI*.*. 



Body posteriorly furnished with cylindrical or conical styli- 

 form appendages, or with none in some genera. 



The genera are Cerapus, Mellta, Amphithoe, Dexamine, 

 Gammarus, Pherusa, Orchestia, Talirus, Atylus, Corophium, 

 Podocerus, Jaf sa, Phronima, and 



Leucothoe articutota, pi. :-(>, f. 16. First pair of limbs didac- 

 tyle, with a double articulate thumb; second pair with a dilated, 

 compressed baud, the thumb of which is crooked ; abdominal 

 extremity bent downwards. 



FAMILY II. UBOPTERA. 



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. DECKMPEUES. 

 Animals provided with ten feet only. 

 The genera are Typhis, Anceus, anil Praniza. 



FAMILY IV. HETEROPA. 



With fourteen feet, in most instances all fitted for s wimmirg 

 on the four last only. 



The genera are lone, and 



Apseude talpat, pi. 30 , f. 17. Antennae four, two external 

 longest ; body elongated, of six joints ; tail elongated, consist- 

 ing of fifteen segments ; two anterior feet didactyle, last lour 

 ciliated, and directed backwards, fitted for swimming. 



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 de- 

 pressed, divided into from three to neven segments ; feet ten or 

 fourteen ; tail varying from one to nine segments, with brunch- 

 ials ; destitute of shell ; eyes granulated ; antennae 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. EPICARIDES. 



Body much depressed above, and concave below, having 

 neither eyes, antennae, mandibles, nor caudal fin. 



But one genus, Bopyrus. 



FAMILY II. CYMOTHOAUBS. 



Eyes and antennae four, sometimes indistinct; mandibles 

 horny ; feet fitted for walking and prehension ; posterior extre- 

 mity 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. 30 , f. 18. Upper antennae with two first 

 joints, broad and compressed; eyes large, somewhat convex; 

 tail foliaceous ; abaominal joints imbricated on their edges. 



FAMILY III. SPH*BOMIDES. 



Post-abdomen with three segments, the last with two leaflets. 

 The genera are Zuzara, Sphaeroma, Campecopea, Nde&a 

 Dviiamene, Cymodocea, and 





