GASTEROPODA. 



GASTRROSTKrs. 



composed of numerous leaflet* or fringe* (lanicres) ranged in |rallcl 

 order like the teeth of a comb (whence their name), are attached ujxra 

 one, two, or three line*, according to the genus, to the plafond of the 

 pulmonary cavity, which occupies the Ust whorl of the shell, and 

 Iiich forma a large opening between the border of the mantle and 

 the body. Two genera only (Cydotloma and l/cliria) have, in the 

 place of branchue, a vascular net covering the plafond of a cavity 

 i-iniilar in other respect* : theae are the only genera which breathe air ; 

 all the other* renpire water. 



All the Ptctinitranckiala have two teuUcula, and two eyes some- 

 time* carried on their proper peduncles, a mouth in form of a 

 proboscu, which it more or lee* elongated, and the *exe* separate. 

 The iutroiniMive organ of the male, which is attached to the aide of 

 the neck, cannot ordinarily be retracted into the body, but is reflected 

 in the branchial cavity, and is sometimes very large, as may be see* 

 in the figure of B*cci*M undalum [ENTOMOSTOMATA ; BuccTM'Mj, 

 which will give a general idea of the form of a marine Pectinibranchiato 

 Testaceous MoUosk with a tnrbinated shell Paludina, indeed, can 

 cause this organ to re-enter the body by an orifice pierced at its right 

 tentacle. The rectum and oviduct of the female creep also along the 

 right ride of the branchial cavity, and between them and the branchitc 

 it a particular organ composed of cellule* containing a very viscous 

 liquor, serving to form a common envelopment or case, which include* 

 the egg*, and which the animal deposits with them. Several of these 

 deposited ovaries present very complicated and singular forma, and 

 jiiay be often found on the sea-beach. 



The tongue of the Ptctinibranchiata is armed with small hooks, and 

 files down the hardest bodies by alow and repeated friction. 



The greatest difference among these animals consists in the presence 

 or absence of the canal formed by a prolongation of the border of the 

 pulmonary cavity of the left Bide, and which passes by means of a 

 similar canal, or by a notch in the shell, so aa to enable the animal to 

 respire without leaving the shelter of its shell. Some of the genera 

 again are without an operculum ; and the species also exhibit differ- 

 ence* in the filament*, fringes, and other ornaments exhibited on their 

 head, their foot, or their mantle. These mollusks are arranged under 

 many families, according to the form of their shells, which, generally 

 speaking, present a sufficiently constant relation to the form of the 

 animal. But the student should remember that this is not a rule 

 without exception, as Dr. Gray has pointed out in his interesting 

 paper in the ' Philosophical Transactions.' 



In this work the reader will find the numerous genera the leading 

 one* at l-at of this moot extensive order, principally under the 

 titles of the different families into which they have been separated by 

 coolagista, and sometimes under their generic appellations. 



7. Tubuliliranc/iiata. 



Cuvier consider* that this order should be detached from the 

 Peciinibranchiata, to which they nevertheless bear great resemblance, 

 because their shell (which is in the form of a tube more or less 

 irregular, the commencement of which only is turbinated or spiral) is 

 fixed to different foreign bodies ; they have in consequence no true 

 copulative organs, and fecundate themselves. Vtrmettu, Alayilut, and 

 .S//.,uura (all marine) belong to this order. 



8. Scutibrancitiato. (Paracepftalophora Jlermajihroditica, with 

 exception of the Chiton*, De Blainv.). 



Thi* order consist* of the Gasteropoda which bear a near relation- 

 ship to the Prctinibranchiata in the shape and position of the branchiic, 

 a* well as in the general form of the body, but which have the sexes 

 united in the same individual. The shells of this order are always 

 without an operculum, very wide in the opening (some of them may 

 be said to be almost all aperture), and many of them have shells 

 without any turbtnation, so that they cover the animal, and especially 

 it* branchiae, like a shield. The heart is traversed by the rectum, and 

 receives the blood by two auricles, a* in the generality of Bivalves. 

 Under this order Cuvier, in his hut edition of the ' Kcgne Animal,' 

 place* the II allot ida (Ear-Shells), Stonatia, Fiuurella, Emarginula, 

 and Parmopkontt. [Fisf BKLUD*; PATILLIDJC.] 



9. CyclvbrancMtala (Cerricolranchiata, Blainv.). 



Branchiic in form of small leaflets or little pyramids, attached in a 

 cordon more or lea* complete under the border* of the mantle, 

 nearly a* in the /*fmbra*ckiala, from which the Cydobrancluata are 

 distinguished by their hermaphroditism ; for they have no organ* of 

 copulation, and can reproduce the species without having recourse to 

 a second individual. The heart does not embrace the rectum, but it 

 varies in situation. [('IIITO.NID.K ; I'ATKI.I.IDJL] 



A general view of the structure and relations of the Shell-Fish is 

 given under Mou.rscx. 



The following is a synopsis of the families and genera of Gatteropoda 

 as given in Mr. Woodward's ' Manual of the Mollusca' : 



Order PUOSOBRAXCHIATA. 



Section A. Siphonottomala. 



Family 1. Ktrombid<r. 



Genera, Strombiu, Pleroctrat, Xottcllaria, Serapkyt. 

 Family 2. Hfurieid*. 



Genera, Uuref, Puania, Rantlla, Triton, Fatcioiaria, 

 Caneellaria, Tridtotropit, I'yrtda, Faint. 



Family 3. ]lcciid<r. 



Genera, Hutciimm, Pteudolira, Anulajc, Ualia, Tertbra, Eliunut, 

 Nairn, Phot, Kingimla (?), I'urpura, P*rpnrina. ilonocerot, 

 Pedienlaria, Ricinula, Planar it, Magiiut, Ctatit, Onitcia, Cithara, 

 Cauidaria, Dolittm, J/arjia, I'uiumbrlla, IMira, Ancillaria. 



Family 4. Coitl<r. 

 Genera, fount, Plturoloma. 

 l-'.iniily 5. Volutitlir. 

 Genera, Valuta, Cynba, Uitra, Volraria, Maiyintlla. 



Family 6. Cypntida. 

 Genera, Cyprtra, Erato, Orulmn. 

 Section B. ffolottomata, 



Family 1. ffatieida. 

 Genera, \alica, Sigarcttu, Lamellaria, Xarica, Vdutina. 



Family 2. PyramideUida. 



Genera, Pyramidella, (Miottomia, CktmU;ia, Stflina, Lojronema, 

 Mackrucktiltu. 



Family 3. Centkiada. 



Genera, Cerilhium, Potamidti, Nerituea, Ptutiijiella, Ai*rrlait, 

 Strulhiolaria. 



Family 4. Melaniada. 

 Genera, Mtlania, Paludoiniu, ifdanoptit. 



Family 5. TnrriteUida:. 

 Genera, Turritclla, Adit, Cireum, Vtrmclta, SUiquaria, Scalaria. 



Family 6. Litorinida. 



Genera, Lilorina, Solarium, Phonu, Lacuna, Lltiopta, Jiitioa, 

 Stenea, Truncatella, Lithoglypliut. 



Family 7. Puludinida:. 

 Genera, Paludina, Ampullaria, Amphibola, Valrata, 



Family 8. Ncritida;. 

 Genera, Xerita, PUtol**, Xtrtiina, Xaritella. 



Family 9. T*rbini<l<r. 



Genera, Turbo, PhatianeUa, Jmperator, Trochtu, Rottlia, Mono- 

 donta, Dtlphinnla, Adeorbit, Enompltaliu, Stomatella, Brodcrifin. 



Family 10. JJaliotidte. 



Genera, Halwtit, Stomatia, Satturella, Pleurotomaria, Murchitoiiia, 

 Trockoltma, Cimu, lantkina. 

 Family 11. J-'iaurellidtr. 

 Genera, Futurtlla, Punctunlla, Kimtda, Emanjiuvla, Parmopfiofut. 



Family 12. Calyptrceidtt. 

 Genera, Calyptrcea, Crepidula, Pdcopti*, J/ipponyx. 



Family 13. PuttUida. 

 Genera, Patella, Acmaa, Gadinia, Siyhonaria. 



Family 14. Dentaliadtt. 

 Genus, Dentalium. 



Family 15. ChUonida. 

 Genus, Chiton. 



Most of the families and more important genera are given under 

 their proper names in this work. 



GASTEROSTEUS, a genus of Fishes, with hard cheeks, belonging 

 to the division Acanthoi>teryyii. The common name of the specie* 

 in this country is Stickleback. This genus is distinguished by the 

 following characters : Anterior dorsal represented only by free spiuex ; 

 body generally scaleless, but protected more or less at the sidi-i l.y 

 shield-like platen ; ventrals reduced to a single spine ; head without 

 spines or tubercles ; brouchiostegous membrane with three rays. 



Several species of Stickleback are found in the ponds and streams 

 of this country, and one species is found in the salt-water ; they are 

 very active and voracious, and live upon aquatic insects and worm*. 



The most common species is the Three-Spined Stickleback (Hotter- 

 ottrut aculeatut. Linn.), which in distinguished by the body being pro- 

 tected at the side* with shield-like plates, and the possession of three 

 spines on the back. It is of an olive-colour above and silvery-white 

 beneath, and varies from 2 to 3 inches in length. In the breeding 

 season the male* assume a pink him on the under parts of the body, 

 and the general colouring of tUu upper parts is brighter, and often 

 green. According to Bloch this species spawns in April and June ; and 

 according to Cuvier in July and August 



The number of scaly plates varies in the sides of the body, and I* 

 supposed by some authors of high authority to afford specific charac- 

 ters. The following are the principal varieties or species established 

 by Cuvier and Yarrell chiefly upon this character. 



0. trackunu, Rough-Toiled Stickleback. (Yarrell, 'Brit FUhcx,' 

 vol. i. p. 76.) The scaly plate* extending the whole length of th<- 

 *ide* ; in number about 30. 



tt temiarmatut, Half-Armed Stickleback (Yarrell). Lateral plate* 

 extending to a vertical line joining the vent and commencement of the 

 soft dorsal ; in number from 12 to 15. 



O. liiurui, Smooth-Tailed Stickleback (Yarrell). Lateral plates 

 extending only a* far a* the end* of the i-ays of the pectoral film, 

 where these hut are laid bock. 



O. brachycentnu, Short-Spined Stickleback (Yarrell). Lateral plate* 

 not extending beyond the pectorals ; dorsal and ventral spines very 

 short 



The above are regarded as varieties of the Gatterottetu aculeaiut, 

 Linn., l.y Mr. Jenyn.-, who observes that that species " U subject to 



