OCR Text |
Show 402 MOLLUSCA. pointed ears, and a more oblique shell. The vestige of a tooth, of which traces are visible in the Pintadinre, is observed on the hinge, befo1·e the ligament. One species, Myt-ilus hirundo, L., Chemn., VIII, lxxxi, 722- 728, that inhabits the Mediterranean, is remarkable for the. pointed ears which extend its hinge on each side. Its byssus is coarse and stout, resembling a little tree( 1 ). PINNA, Lin. The Pinnre have two equal valves, forming a segment of a circle, or resembling a half-opened fan, which are closely united by a liga· ment along one of their sides. The animal, the C:fnM.lERA, Poli, is elongated, like its shell; the lips, branchire, and other parts are in the same proportion. The mantle is closed along the side of the liga· ment; the foot resembles a little conical tongue excavated by a sui· cus; it is furnished with a small transverse muscle situated at the acute angle formed by the valves, near which is the mouth, and with a very large one in their broader portion. By the side of the anus, which is behind this large muscle, is a conical appendage, peculiar to the genus, susceptible of expansion and elongation, the use of which is unknown(2). The byssus of several species of Pinna is as fine and brilliant as silk, and is employed in fabricating the most precious stuffs. Such is the P. nobilis, L., Chemn. VIII, lxxxix; which is moreover re· cognized by the valves being roughened with recurved and semi· tabular plates. It remains half buried in the sand, and anchored by its byssus(3). In the AReA, Lin. ( 4) The valves are equal and transverse, that is to say, the hinge occu· pies the longest side. It is furnished with a large number of small teeth, which interlock with each other, and, as in the subsequent ge· nera, with two fasciculi of transverse and nearly equal muscles, in· (1) Several species are now made of it. See Lam., An. sans Verteb., VI, part I, p. 146, et seq. (2) M. Poli calls it also an abdominal trachea, just as erroneously as he applies the same name to the foot of the Pectines, &c. (3) The whole genus Pinna may remain as it is in Gmelin: it is well to remem· ber, however, that some of his species may be found to form but one. See also Lam., An. sans Vert., VI, part I, p. 130, et seq., and Sowerb., Gen. of Shells, No. XXVI. ( 4) M. de Blain ville forms his family of the Anc.&cE.& or PouonoN'l':ES, from the genus Anc.&. ACEPHALA TESTACEA. 403 serted into the extremities of the valves, which serve to close them. In the ARoA, Lam., Or the Arcre propedy so called, the hinge is rectilinear, and the shell most elongated in a direction parallel to it. The summits are generally convex, and curve over the hinge, but are separated from each other. The valves do not close perfectly in the centre, because there is a horny plate or tendinous fillet before the abdomen of the animal(!) that serves for a foot, and by which it adheres to submerged bodies. They are found in rocky bottoms near the shore, and are usually covered with a hairy epidermis. They are not much esteemed for the table. Some species are found in the Mediterranean(2), and a great many fossil, in strata anterior to chalk, particularly in Italy. Certain Arcre in which the teeth of the two ends of the hinge assume a longitudinal direction, are distinguished by Lamarck under the name of CuouLL1EA(3). We ought also, it is probable, to separate the species with well marked ribs, and completely closing and interlocking edges; for we must presume that their animal is not fixed, but rather resembles that of a Pectunculus( 4 ). We have a still better warrant for removing the .llrca tortuoaa, Chemn., VIII, liii, 524, 525, in its fantastic figure and unequallv oblique valves( 5). • PEoTuNouLus, Lam. The hinge forming a curved line, and the shell lenticular; the valves always close completely, and their summits are approximated. The animal, AXIMEA, Poli, is furnished with a large compressed foot ~ith a double inferior margin which enables it to crawl. They live m ooze. Some species are found on the coast of France(6). (1) The DAPHNE, Poli. (2} .llrca Nom, Chemn., VII, liii, 529, 531;-.flrca barbata, Id., liv, 535, 537;./ l..ovata, lb., 538;-Jl; magellanica, lb. 539;-.fl. reticulata, lb. 540;-.fl. candida, ld., lv, 542, 544;-.fl. indica, lb., 543;-.f.l. cancellata, Schrred., Intr., III, ix, 2. (3) .llrca cucullata, Chemn., VII, liii, 526, S28;-Cuculla3a crassatina, Lam., Ann. du Mus., VI, 338. (4) .llrca antiquata, L. Chemn., VII, lv, 548, 549;-.fl. senilis, ld., lvi, 554, 556; ;.!l.:gra~sa, lb. 557;-Jl. corbiculata, lb., 558, 559;-.9.. rlwmboi"dea, lb., 553;. Jamauensis, List., 229, 64. (S) It forms the genus Tnxsxs, Oken. ./1 (6) .llrca pilosa, L., Chemn., VII, lvii, 565, 566;-.0.rc. glycime1is, lb., 564;~ decus3ata, lb., 561;-.9.. requilatera, lb., 562;-.9.. undata, Jb., 560;-.fl. mamw· r a, lb., 563;-.9.. pectunculus, Id., I viii, 568, 569;-.fl. pectinata, Jb., 570, 571. |