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Show ' 432 MOLLUSCA. CLASS V. BRACHIOPODA( I). The Mollusca Brachiopoda, like the Acephala, have a hilobed mantle which is always open. Instead of feet they are provided with two fleshy arms, furnished with numerous fila· ments, which they can protrude from, and draw into the shell. The mouth is between the base of the arms. Neither their organs of generation, nor their nervous system are well known. All the Brachiopoda are invested with bivalve shells, fixed and immovable. But three genera are known. LINGULA, Brug. Two equal, flat, oblong valves, the summits of which are at the extremity of one of the narrow sides, gaping at the othet· end, and attached between the two summits to a fleshy pedicle, which suspends them to the rocks; the arms become spirally convoluted pt·e· viously to entering the shell. It appears that the branchire consist of small leaflets, disposed around the internal face of each lobe of the mantle. But a single species-Lingula anatina, Cuv., Ann. du Mus., I, vi, Seb., III, xvi, 4, is known. It inhabits the Indian Ocean, and has thin, horny and greenish valves(2). (1) M. de Blainville has given to my BnA.cHioroDA. the name of P ALLIOBRU· cuu.·u, and makes an order of them in his class of the AcEPHALoruoxu. (2) Linnceus, who knew but one of the valves, called it Patella unguis. Solander and Chemnit:z:, who were aware of its having two, called it, the one, Mytilus lingua, and the other, Pinna unguis. Brugieres knew its pedicle, and consequently made a genus of it by the name of LINGULA, Encyc. Method., Vers, pl. 250. It is singular that before us, no one had remarked that it is well figured with its pedicle by Seba, loc. cit. B RACHlOPODA. 433 TEREBRATULA, Brug. Two unequal valves u~ited by a hinge; the summit of one, more salient than the other, IS perforated to permit the passage of a fleshy pedicle which attaches the shell to rocks, madrepores, other shells, &c. Internally, a small bony piece of frame-work is observed, that is sometimes very complex, composed of two branches which articulate with the unperforated valve and that support two arms edged all round with a long, close fringe, between which, on the side next to the large valve, is a third, simply membranous and much longer appendage, usually spirally convoluted, and edged, like the arms, with a fine and close fringe. The mouth is a small vertical fissure between these three large appendages. The principal part of the body, situated near the hinge, contains the numerous muscles which reach from one valve to the other, and between them are the viscera, which occupy but little space. The ovaries appear to be two ramified productions, adhering to the parietes of each valve. I have not yet been able to ascertain exactly the position of the branchire. Numberless 'ferebratulce are found fossil or petrified, in certain secondary strata of ancient formations(!). The living species are less nurnerous(2). The shell of some is transversely broader or longer, in a direction perpendicular to the hinge, with an entire or emarginated contour, with two or several lobes; some of them are even triangular; the surface is smooth, sulcated in radii, or veined; they are thick or thin, and even diaphanous. In several of them, in lieu of the hole in the summit of the thin valve, there is a notch, and this notch is sometimes partly formed by two accessory pieces, &c. It is probable that when better known their animals will present generic differences. Already in the SPIRIFER, Sowerby, Two large cones have been recognized, formed of a spiral thread, which appear to have supported the animal(s). In (1) M. Defrance distinguishes upwards of two hundred. (2) .!lnomia awbinata, Gualt., 96, A;-.lln. aurita, Id., lb., B;-.lln. retusa,·-.lln. truncata, Chemn., Vill, lxxvii, 711;-.lln. capensis, lb., 703;-.ll.n. pubescens, ld., lxxviii, 702;-.lln. detruncata, lb., 705;-.lln. sanguinolenta, lb., 706;-.lln. vitrea, lb ., 707, 7'09;-An. dorsata, lb., 710, 711; .lln. psittacea, lb. 713; .lln. cranium, &c. For the fossil species see Encyc. Method. Vers, pl. 239-246. (3) For this genus see Sowerb., Min. Conch. and the article Spirijere o£ M. Defrance, Diet. des Sc. Nat. t. L. VoL. Il.-3 E |