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Show 344 MOLLUSCA. ganization observed in Doris and Tritonia, but their branchire, instead of being placed on the back, resemble two long series of laminre, situated on the two sides of the body, under the projecting margin of the mantle. PHYLLIDIA, Cuv. The mantle naked, usually coriaceous, and without any shell; the mouth, a small proboscis, each side of which is furnished with a tentaculum; two others project from above two small cavities in the mantle. The anus is on the hind part of the mantle, and the genital orifices forward, under the right side; the heart near the middle of the back; the stomach simple and membranous, and the intestine short. Several species inhabit the Indian Ocean( 1 ). DIPHYLLIDIA, Cuv. The branchire similar to those of the Phyllidire, but the posterior part of the mantle more pointed; on each side of the semicircular head a pointed tentaculum and a slight tubercle; the anus on the right side(2). I ORDER IV. TECTIBRANCHIAT A(3). The branchire along the right side or on the back, composed of laminre more or less divided, but not symmetrical ; they are (1) Phyllidia trilineata, Seb., lll, i, 16; Cuv., Ann. du Mus., V, xviii, 1; and Zool., Voy. Freycin., pl. 87, f. 7-10;-Ph. ocellata, Cuv., lb. 7;-Ph. pmtulo&a, Id. lb. 8, and some new species. (2) Diphyllidia Brugmansii, Cuv. ;-Diphyll. lineata, Otto., Nov. Act. N~~· Cur., X, vii, or Pleuro-phyllidia, Meckel., G.erm. Archiv., VIII, p. 190,pl. u, delle Chiaie, Mem., X, 12. N.B. The Linguelle of Elfort, Blainv., Malac., pl. xi vii, f. 2, does not appear to differ from our first species. (3) M. de Blainville bas given to this order the name of MoNOPLJJtraouAJ· tttU.TA, GASTEROJ:'ODA TECTIBRANCHIA T A. 345 more or less covered by the mantle, in which a small shell is generally contained. They approach the Pectinibranchiata in the form of the organs of respiration, and like them inhabit the Ocean; but they are all hermaphrodites like theN udibranchiata and the Pulmonea. PLEUROBRANCHus, Cuv. The body equally overlapped by the mantle and by the foot, as if it were between two shields. In some species a little oval calcareous lamina is contained in the mantle, and a horny one in that of others; the mantle is emarginated above the head. The branchire are attached along the right side in the furrow, between the mantle and the foot, forming a series of pyramids divided into triangular laminulre. The mouth, a small proboscis, is surmounted by an emarginated lip and by two tubular and cleft tentacula; the genital orifices are before, and the anus behind the branchire. There are four stoli.lachs, the second of which is fleshy and sometimes armed with bony appendages, and the third, furnished internally with salient longitudinallaminre; the intestine is short. Various species inhabit both the Mediterranean and the Atlantic, some of which are large and marked with the most beautiful colours( 1 ). PLEUROBRANCHJEA, Meckel.-PLEUROBRANCHIDIUM, Bl. The branchire and genital orifices situated as in Pleurobranchus; but the anus is above the branchire, the margin of the mantle and foot project but little, and on the fore part of the former are four short, distant tentacula, forming a square that reminds the observer of the anterior disk of the Acerre. I can find but one stomach, which is merely a dilatation of the canal, with thin parietes. (1) Plet''~'Obranchua Peronii, Cuv., Ann. du Mus., V, xviii, 1, 2;-Pl. tubercu. latw, Meckel., Anat. Compar., I, v, 33-40; and some new species, such asthePleur. oblongus, Descr. de l'Eg., Moll. Gaster., pl. iii, f. l;-Pl. aurantiacw, Id., Uisso., Hist. Nat. Merid. IV, pl. i, f. 8;-Pl. lwnicepa, Cuv.;-Pl. Forakalii, Forsk., pl. xxviii, and Leuckard, App., Uuppel., An. Invert., pl. v;-Pl. citrinw, lb., f. 1. The genus LAMELLARIA, Montag., Lin. Trans., XI, pl. xii, f. 3 and 4, does not appear to me to differ in any essential point from Pleurobranchus; the same observation applies to the BERTHllLLA of Blainv., Malac., pl. xliii, f. 1. The latter it distinguished merely because the mantle is not emarginated above the head, as is ~he case in many species ofPleurobranchus. The Pl. oblongua would belong to 11' and even the Pl. lunicep8• Vot. II.-2 T . |