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Show 378 MOLLUSCA. TEREBRA, Brug. The aperture, emargination and columella of a t1·ue Buccinum; but the general form is turriculated, that is to say, the spire is length-ened into a point( 1 ). In the CERITIIIUM, Brug., Very properly separated from the M UREX of Lin nee us, we observe a shell with a turriculated spire; the aperture is oval, and the canal short, but well marked, and reflected to the left or backwards. The animal has a veil on its head, and is furnished with two separated tentacula, on the side of which are the eyes, and with a round, horny operculum. Many are found fossil(2). M. Brongniart separates from the Ce-rithia the PoTAMIDA, Brongn. Which, with the same form of shell, has a very short and scarcely emarginated canal, no sulcus on the upper part of the right margin, and the external lip dilated. The Potamidce inhabit rivers, or at least ~heir mouths, and fossil specimens are found' in strata, which contain other fresh-water or land species only(3). The genus ( 1) The whole of the last subdivision of the Buccina, Gmelin, such as, Buccinum maculatum, L., 846, 74;-Bucc. cre:nulatum, L. List., 846, 75;-Bucc. dimidi· atum, L., List., 843, 71;-Bucc. subulatum, L., List., 842, 70, &c. M. de Blainville separates from them the genus SuBULA, which he founds on a difference in the animal, and moreover on the presence of an operculum. (2) Murex vertagus, List., 1020, 83;-.M. aluco, List., 1025, 87;-M. annuklru, Martini, IV, clvii, 1486;-M. cingulatus, lb., 1492;-.M. terebella, Id., clv, 1458, 9;-.M. fuscatus, Gualt., 56, H;-.M. granulatus, l\1:\rtini, IV, clvii, 1483;-M. moluccanus, lb., 1484, S. &c., with the numerous fossil species described by M. de Lamarck, Ann. du Mus. M. Deshayes has separated from the Cerithia, under the name of NEVINEA, some small species, where the margin is prolonged into the aperture, and divides it into three distinct orifices. It is also near the Cerithia that we must place several fossil shells, which form th~ genus NERINl:A of M. Deft·ance, and which is distinguished by strongly marked phcre on each whorl and on the columella, the centre of which, besides, is hollow throughout. Nine species are already ascertained. (3) R~e ~rongn., Ann. du Mus., XV, 367. In this subg·enus should be placed the Oerzth~u":" atrum, Brug., List., pl. 115, f. 10;-0er. palustre, f. lb., 836, f. 62;-.?· muncatum, lb., 121, f. 17, &c., and among the fossils, the Potami®La· marki~, Brongn., loc. cit. pl. xxii, f. 3. GASTEROPODA FECTINIBRANCIIIATA. 379 ~UREx, Lin.(l) Compt'ises all those shells in which there is a salient and straight canal(2). The animal of each subgenus is furnished with a proboscis, long approximated tentacula on the external side of which are the eyes, and with a horny operculum; the veil on the head is wanting; and, the length of the siphon excepted, it otherwise resembles that of the Buccina. B1·ugiere divides them into genera, which have been since subdivided by Messrs Lamarck and Montfort. The MuREx, Brug. Includes all those which have a salient and straight canal, with varices across the whorls(3). Lamarck appropriates this name to those in which the varices are not contiguous on two opposite lines. If their canal be long and slender, and the varices armed with spines, they become the MUilEx, properly so called, of Montfort( 4). When, with this long canal, the varices are mere knobs, they form the BnoNTis, Montf.(s) Some of them, which, with a moderate canal, have projecting tubes that penetrate into the shell between spiny varices, constitute the TYPHis, Montf.(6) When, instead of spines, the varices are furnished with plicated lamellce, alashed, or divided into b1·anches, they are the CHIOORAOEA, Montf.(7) Their canal is long and moderate, and theil· foliaceous productions vary infinitely in figure and complication. When, with a moderate or short canal, the varices are mere knots, (1) This great genus forms the family SxPHONOSTOMA, Blainv. ~2) To which Linnreus also added several Purpurre in which the, canal is not saltent, and all the OeritMa in which it is recurved. (3) Varices are knobs with which the animal borders its mouth, at each interruption in the growth ofits shell. (4) Murex tribulus, List., 902, 22;-Mur. brandaris, List., 900, 20;-Mur. cornutUB, List., 901, 21 ;-Mur. senegale:nsis, Gm., and the costatus of No. 86, Adans. Seneg., VllJ, 19. (5) Murex haustellum, List., 90J, 23;-Mur. caudatus, Martini, Conch., lli, f. 1046,1049;-Mur. pyrum. (6) Murex tubifer, Roissy, Brug., Journ. d'Hist. Nat., I, xi, S: Montfort, 614 (7) ltfurex ramosus, List., 946, 41, and all its varieties; Martini, III, cv, ex, cxi; -Mur. scorpio, Martini, cvi;-Mu1·. saa;atilis, l\1tu'tini, cvii, eviii, and several others not yet well characterized. |
