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Show 340 MOLLUSCA. ONCHIDORA, Blainv. Only differs from Doris in the separation of the ~enital organs, the orifice of which communicates by a furrow runmng along the right side as in Onchidium(l). In the PLoCAMOCERos, Leuck. We find all the characters of the Onchidorce, in addition to which the anterior margin of their mantle is ornamented with numerous branched tentacula(2). PoLYCERA, Cuv. The branchire, as in Doris, on the hind part of the body, but more simple, and followed by two membranous la~ince, which cove~ t~em in moments of danger; anterior to the claVlform tentacula, s1mtlar to those in Doris, are four, and sometimes six others, simply point· ed(s). TRITONIA, Cuv. The body, superior tentacula and genital organs as in Doris; but the anus and the orifice through which the peculiar liquid is excreted, are on the right behind the organs of generation: the branchire, which resemble little trees, are arranged along the sides of the back, and the mouth, provided with broad membranous lips, is armed in· side with two horny and trenchant lateral jaws, which may be com· pared to a pair of sheep-shears. Trit. Hombergii, Cuv., Ann. du Mus., I, xxxi, 1, 2, and the lb ., Id., 3;-D. solea, ld., lb., 1, 2;-D. scabra, Id., lb., p. 446;-D. maculo.!a,Id., lb. ;-D. tomentosa, ld., lb. ;-D. nodo:Ja, Montag., Lin, Trans., IX, vii, 2;-D. marginata, Lin., Trans., VII, vii, p. 84;-D. nigricans, Otto., Nov. Act. Nat. Cur., XIII, part II, pl. xxvi, f. 1;-D. grandijlorq, Id., lb., XXVII, f. 3;-D. tigrina, SaY. Egyp., Gasterop., pl. i, p. 3;-D. concenlrisca, lb., f. 5;-D. marmorata, lb., f. 6, &c. , Prismatic species, where the mantle is almost as narrow as the foot: DoriJ lacera, Cuv., Ann. du Mus., IV, lxxiii, f. 1 and 2;-D. atromarginata, Id., lb ., lniv, 6;-D. pmtulosa, Id., lb., p. 473;-D. gracilis, Rapp., Nov. Act. Nat. Cur. XIII, part ll, pl. xxvii, f. 10. See also Van Hassel. Bullet. Univ., 1824, Octob., Zoo!., p. 235. ( 1) Onchidora Leachii, Blainv., Malac., pl. xlvi, f. 8. (2) Plocamoceroa ocellatus, Leuck., App. Ruppel., Invert., pl. 5, f. S. ( 3) Doria quadrilineata, MUll., Zoo}., Dan., I, xvii, 4-6, and better, .!b., cxxxviii, 5-6;-D. cornuta, lb., cxlv, 1, 2, 3;-D. jlava, Lin. Tl'ans., VU, vu, P· 84;-Polycera lineata, Risso, Hist., Nat., IV, pl. i, f. 5. GASTEROPODA NUDIBRANCHIAT A. 341 Journ. de Phys., 1785, October, pl. ii. A large species of a copper colour, from the coast of France. The same locality produces many others which vary greatly in size and the form of their branchice(l ); several of them are very small(2). THETHYs, Lin.(3) Two rows of branchice resembling branching tufts along the back, and a very large membranous and fringed veil on the head, which shortens as it curves under the mouth; this latter is a membranous proboscis without jaws; on the base of the veil are two compressed tentacula, from whose margin projects a small conical point. The orifices of the genital organs, of the anus, and of the peculiar fluid are situated as in the Tritonice. The stomach is membranous and the intestine very short. T. fimbria, L.; Cuv., Ann. du Mus., XII, xxiv( 4). Grey, spotted with white; a beautiful species from the Mediterranean. ScYLLJEA, Lin. Body compressed; the foot narrow and marked with a furrow which enables it to clasp the stems of the fuci; no veil; the mouth resembling a little proboscis; orifices as in Thethys; the compressed tentacula terminated by a cavity, from which issues a little uneven point, and two pairs of membranous crests on the back, the internal surface of which is furnished with pencils of filaments, which are the branchire. The middle of the stomach is invested with a fleshy ring, internally armed with horny and trenchant lamince, like knives. (1) Such are Trit. elegans, Desar. de l'Eg., Zool., Gaster., pl. 2, f. 1;-Trit. rubra, Leuck., App., Rupp., Invert., pl. 4, f. 1;-Tr. glauca, lb., f. 2;:-T. cyanobranchiata, lb., f, 3;-T. arborescens, Cuv., Ann. du Mus., VI, b:1, and three others, at least closely allied;-Doris arborescens, Strrem., Act. Hafn., X, ;• 5;Doria frondosa, Ascan., Act. Dronth., V, v, 2, and Doris ce1·vina, Bomme, Act. Fless., I, iii, 1. .. (2) Doris co1·onata, Bomme, lb., and Doris pinnati.ftda, Lin. Trans., VII, vu, which is closely allied to it;-Doria jimbriata, MUll., Zool. Dan., CXX~VIU, 2, and probably Dori.3 clavigera, Mull., lb., XVII, 1-3. Perhaps the Dorzs lacera, Zool. Dan., CXXXVIII, 3, 4, should also be referred to this genus. . . (3) From &e&uC~tv, a name employed by the ancients to designate the Ascidtre; Linnzus applied it to this genus. . (4) The difference observed between the Thethya jimbriata, Bohatsch., Amm. Mar., pl. v, and the 'l'hetltysleporina, Fab., Column., Ag., pl. xxvi, appears to me to be the result of a greater or less degree of preservation. |