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Show 320 MOLLUSCA .. CLASS II. PTEROPODA(!). The Pteropoda, like the Cephalopoda, swim in the ocean, but being deprived of feet, can neither fix themselves to other bodies, nor crawl. Their organs of locomotion consist of fins placed like wings on the two sides of the mouth. But few and small species are known, all of them hermaphrodites. CLIO, Lin.-CLIONE, Pall. Body oblong, membranous, without a mantle; head formed of twCY rounded lobes, whence originate small tentacula; two small fleshy lips, and a little tongue on the front of the mouth; the fins covered with a vascular net-work which acts as branchire, the anus and geni· tal orifice under the right one. Some authors consider them as pos• sessing eyes. The external envelope is far from being filled with the viscera; the stomach is wide, the intestine short, and the liver voluminous. Clio borealis, L. This species, which is the most celebrated, is found in astonishing numbers in the arctic seas, furnishing, by its abundance, food for the whales, although each individual is hardly an inch long(2). Brugiere has observed a larger and not less abundant species in the Indian Ocean; it is distinguished by its rose colour, emar· (1) M. de Blainville unites my Pteropoda and my Ga8teropodaina. single class, \thich he calls P AR.A.CEl'UALOl'ltOnA, of which my Pteropoda form a particular order, under the name of Al'ononnANCHIAT.A.. This order is divided into two families; the Tltecosoma, which are furnished with a shell, and the Gymnosoma which are not. (2) The Clio borealis of Pallas (Spicil., X, pl. 1, f. 18, 19), the Clio retusa of Fabl'icius (Faun. Groen., L., 334), and the Clio lamaci~ of Phips (Ellis, zooph., pl. 15, f. 9, 1, 10), of which Gmelin makes as many different species, appear to be this same animal. PTEROPODA. 321 ginated tail, and the division of the body, by grooves, into six lobes, Encycl. Meth., PI. of the Mollusc., pl. lx:x.v, f. 1, 2. CYMBULIA, Peron. A cartilaginous or gelatinous ~nv~lope .resembling a galley, or rather .a sa.bot or wooden shoe! bnsthng With small points disposed in Jongitudm~l rows •. The ammal has two large wings composed of a vascular u.ssue~ wluc~1 are its branchire and fins; between them, 011 the open .side, IS a third and smaller lobe with three points. The mouth with two small tentacula is situated between the wings towards the closed side of the shell and above two small eyes, and the genital ~pertur~, when.ce issues a small peni~ in the shape of a little proboscis. It IS so diaphanous, that the heart, brain, and viscera can be distinguished through the envelopes( 1 ). PNEUMODERMON, Cuv. The Pneurnoderma begin to be a little further removed from the Elias. Their body is oval, without a mantle and without a shell· the branchire are attached to the surface and composed of little Ia~inre arranged in two or three lines so disposed as to form an H on the part opposite to the head. The fins are small; the mouth furnished with .two small lips and two buncHes of numerous tentacula, each termmated by a sucker, has a little lobe or fleshy tantaculum beneath( 2). Pneumodermon Pe1·onii, Cuv. Ann. du Mus., IV, pl. 59; and P.eron, I~., ::CV, pl. 2. Not more than an inch long. This spectes, which 1s the most common, was captured in the Ocean by Peron. LIMACINA, Cuv. The Limacinre, according to the description of Fabricius, should be clos~ly related to the Pneumoderma; but their body terminates in a spirally convoluted tail, and is lodged in a very thin shell formed . (1) See Peron, Ann. Mus., XV, pl. iii, f. 10-11. N.B. In the fig. of Cymbulia, given by Blainville, Malac., XLVI, the position of the animal in the shell is directly the reverse ()f the true one. Our description is founded upon the recent and repeated observations of M. Laurillard. (2) M. de Blainville once thought that the fins supported the branchial tissue, and that what I lnwe considered as branchire is another kind of fin. In this case :~e analogy with the Clios would have been greater; but since then, (Malacol., p. 3) that gentleman has adopted my views. VoL. II.-2 Q \ |