576 



SUPPLEMENT. 



for locomotion, but, being situated near the 

 mouth, assist in the operation of feeding. 



The nervous system consists of a ganglion 

 or brain situated above and before the intes- 

 tinal canal, with a continuous elongated double 

 chord, having ganglions placed on the lower 

 surface of the body, extending, in some in- 

 stances, its whole length ; while in others, it 

 consists of a central medullary circle, with 

 radiated elongations. 



Many of the crustaceous animals have an 

 acute faculty of sight ; a number of them also 

 possess the senses of smell and taste; but from 

 their shelly envelope their sense of feeling 

 must be very blunt : while their touch must 

 be very sensible, from the number of tentacula 

 possessed by many of them. 



Lamarck divides the Crustacea into five or- 

 ders. 



ORDER I. DECAPODA. 



The head is not distinct from the trunk; branchiae 

 formed like leaflets, close to the base of the four feet- 

 jaws, and hidden under the sides of the shell. 



SECTION I. BRACHYURA. 



Branchiae, seven on each side, moving on a common 

 axis; post-abdomen, bent underneath; generally re- 

 ceived into a cavity beneath the prae abdomen; without 

 a fin at the termination. 



FAMILY I. QUADRILATERA. 



Thorax nearly square, frequently heart-shaped; an- 

 terior angles expanded ; posterior extremity transverse- 

 ly truncated; front protruded, more or less inclined; 

 none of the feet terminated by a fin. The genera of 

 this family are Octypoda, Gelasimus, Myctris, Pinno- 

 therel, Gecarcinus, Plagusia, Grapsus, Gonoplax, Thes- 

 phusa, and Eriphia. TM'phusafluviatilis, pi. 23, fig. 1. 



FAMILY II. ARCUATA. 



The shell anteriorly arched, to nearly the centre of 

 the sides ; posteriorly narrowed and truncated. The 

 genera are, Pilumnus, Cancer, Pirimela, Atelecyclus, 

 Podophthalmus, Lupa, Portunus, Thia, and Portunus 

 corrugatus, pi. 23. f. 2. 



FAMILY III. ORBICULATA. 



Orbicular, narrowed before, usually with two furrows ; 

 exterior feet-jaws with their third joint triangular. The 

 genera are, Matuta, Orithyia, Corystes, Leucosia, and 

 Hcpatus. Leucosia Urania, pi. 23, f. 3. 



FAMILY IV. CRYPTOPODA. 



Nearly triangular; vaulted, and dilated at the pos- 

 terior angles, for the feet in repose : with large, crested, 

 and compressed forceps. The genera are, CEthra and 

 Calappa tuljerculata, pi. 23, f. 4. 



FAMILY V. TRIGONA. 

 Subovoid or triangular ; anterior extremity compressed 



Leptopodia, Pactolus, and Lithodes. Pisa tetraodon, 

 pi. 23, f. 5. 



FAMILY VI. NOTOPODA. 



Having two or four posterior feet, inserted on the 

 back, or somewhat above the line of the rest, The 



genera are, Homola, Ran'ma, Dromia, and Donppe. no- 

 dulosa, pi. 23, f. 6. 



SECTION II. MACROURA. 



Bodies longer than in former section; post-abdomen 

 carinated above; antennae terminated by filaments. 



FAMILY I. HIPPIDES. 



Last abdominal segment lengthened, and foliaceous; 

 two anterior feet, tapering; frequently with a monodac- 

 tylous hand; sometimes with a claw; the other six feet 

 with their last joint fin-shaped. The genera are, Al- 

 bunea, Hippa, and Remipes testudinarius, pi. 23, f. 7. 



FAMILY II. PAGURII. 



Shell but slightly crustaceous; two anterior feet di- 

 dactyle ; next four pairs with long acute tarsi ; last four 

 pairs smaller, terminating with a forceps; sometimes 

 with a pointed hook. The genera are, Birgus, and Pa- 

 (jurus laticauda, pi. 23, f. 8. 



FAMILY III. PALINURINI. 



Terminated by a fan-shaped post-abdomen, produced 

 by the lateral appendages of the last and preceding 

 segments. There is but one genus: Polinurus locustu, 

 pi. 23, f. 9. 



FAMILY IV. SYLLARIDES. 



Having the peduncle formed like a depressed crest. 

 The genera are, Thenus and Scyllarus. 



FAMILY V. GALATHIN.E. 



Feet all alike, but the two anterior, which are diduo- 

 tyle. The genera are, Eryon, Magalopa, Galathea. 

 Porcellana platycMes, pi. 23, f. 10. 



FAMILY VI. ASTACIN.E. 



Four or six of the anterior feet didactyle; terminating 

 abdominal exterior leaflets, entire in some, and in others 

 divided by a suture. The genera are, Thalassina, Gebin, 

 Axius, Callianassa, Nephrops, and Astacus Marinus, pi. 

 23, f. 11. 



FAMILY VII. CARIDES. 



Intermediate antennae placed above the lateral ones, 

 protruding with two or three filamentary terminations, 

 The genera are, Penaeus, Stenopus, Alpheus, Hippolyte. 

 Autonomea, Gnathophyllum, Hymenocera, Nika, 

 Athanas, Atya, Egeon, Crangon, Pandalus, Paaipheea, 

 and Palcemon Serratus, pi. 23, f. 12. 



FAMILY VIII. SCHIZOPODA. 



Feet slender, filiform, fitted for swimming only; one 

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

 appendage, or deeply cleft, or multifid at their extrem- 

 ity. The genera are. Mysis, Zoea, and Nelalia Herbtttii. 

 pi. 23, f. 13. 



ORDER II. STOMAPODA. 



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

 lower appendages of the post-abdomen; head, distinct 

 from the trunk, large, and separated into two parts; 

 shell, membranaceous; intermediate antennae with two 

 or three filaments at their terminations ; six posterior 

 feet filiform; body terminated by a foliaceous fin. 



FAMILY I. UNIPELTATA. 



With an elongated and narrow body; eyes and inter- 

 mediate antennae placed on an anterior elongation of 

 the thorax; exterior feet-jaws, and four anterior limbs, 

 terminated by a monodactyle forceps; the other six 

 limbs fitted for swimming, with the last joint brush- 

 shaped; lateral antennae having a scale at the base; in- 

 termediate ones trifilamcntary. The genera are, Squilla, 

 Erichthus, and A lima Ifyufina, pi. 23, f. 14. 



