44 JiOLLUSCA. 



PHYLLIDIA, Cuv. 



The mantle naked, usually coriaceous, and without any shell; the 

 mouth, a small proboscis, each side of which is furnished with a ten- 

 taculum ; 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*. 



DlPHYLLIDIA, Cuv. 



The branchiae similar to those of the Phyllidise, 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 sidef . 



ORDER IV. 

 TECTIBRANCHIATA J. 



Have the branchiae attached along the right side or on the back, 

 in the form of leaflets, more or less divided, but not symmetrical ; they 

 are more or less covered by the mantle, in the thickness of which a 

 small shell is generally contained. They are approximated to the 

 Pectinibranchiata by the form of the organs of respiration, and like 

 them inhabit the ocean; but they are all hermaphrodites like the 

 Nudibranchiata and the Pulmonea. 



PLEUROBARCHUS, Cuv. 



Have the body equally overlapped by the mantle and by the foot, as 

 if it were between two shields. In some species a little oval calca- 

 reous lamina is contained in the mantle, and a horny one in that of 

 others; the mantle is emarginated above the head. The branchiae 



* Phyllidia trilincata, Seb., Ill, i, 16; Cuv., Ann. du Mus., V, xviii, 1; and 

 Zool., Voy. Freycin., pi. 87, f. 710; Ph. ocellata, Cuv., Ib. 7; Ph. pustulosa, 

 Id. Ib. 8, and some new species. 



f Diphyllidia Bnigmansii, Cuv. ; Diphyll. Uneata, Otto., Nov. Act. Nat. Cur., 

 X, vii, or Pleuro-phyllidia, Meckel., Germ. Archiv., VIII, p. 190, pi. ii, delle 

 Chinie, Mem., X, 12. 



N.B. The Linguelle of Elfort, Blainv., Malac., pi. xlvii, f. 2, does not appear to 

 differ from our first species. 



J M. de Blainville has given to this order the name of MONOPLEUROBRAN- 



CUIATA. 



