GASTEROPODA NUDIBR ANCHIATA. 339 



ORDER TI. 



NUDIBRANCHTATA(l). 



The Nudibranchiata have no shell whatever ; neither are 

 they furnished with a pulmonary cavity, their branchiae being 

 exposed on some part of the back. They are all hermaphro- 

 ditical and marine animals, frequently swimming in a reversed 

 position, with the foot on the surface, concave like a batteaux, 

 and employing the margin of their mantle and their tentacula 

 as oars. In the 



Doris, Cuv.(2) 



The anus opens on the posterior part of the back, the branchiae being 

 arranged in a circle round it, under the form of little arbusculse, the 

 whole resembling a sort of flower. The mouth is a small proboscis, 

 situated under the anterior margin of the mantle, and furnished with 

 two little conical tentacula. Two other claviform tentacula arise 

 from the anterior superior part of the mantle. The openings of the 

 genital organs are approximated under its right margin. The sto- 

 mach is membranous. A gland interlaced with the liver excretes a 

 peculiar fluid through a hole near the anus. The species are nu- 

 merous, and some of them large. They are found in every sea, 

 where their ova, resembling gelatinous bands, are diff'used over 

 stones, sea-weed, &:c.(3) The 



(1) My four first orders are united by M. de Blainville in what he terms a sub- 

 class, designating them by the name of Pakacephalophoha Monoica. He makes 

 two orders of my Nudihranchiata; in the first, or the Ctclobhanchiata, he places 

 Boris and other analogous genera: in the second, or the PoLrBRANCiiiATA, are 

 Tritonia and the following genera, which he divides in two families, according to 

 the presence of two or four tentacula. 



(2) A name first applied by Linnseus to an animal of this genus, which, how- 

 ever, he characterized badly. It was afterwards extended by Muller and Grnilin 

 to almost the whole of the Nudlhrunchiuta, and i-estored by me to its original sig- 

 nification. 



(3) Species with an oval mantle projecting beyond the foot: Doris ven-ucosa, 

 L., Cuv., Ann. du Mus., IV, Ixxiii, 4, 5; — Doris argo, L., Bohatsch, Anim. Mar., 

 V, 4, 5; — Dm-is obvelata, Miill., Zool. Dan., XLVIII, 1, 2; — Dm-is fusca, Id., lb., 

 LXVII, 6, 9; — Doris sfeUata, Bomme, Act. T'less., I, iii, 4; — Doris pilosa, Miill., 

 loc. cit. LXXXV, 5—8;—D. Iwvis, Id., lb., XL VII, 3—5;—D. muricata. Id., 

 L'XXXV, 2— 4;— fl. tuberciilata, Cuv., Ann. du Mus., IV, Ixxiv, 5;—D. limbaia, 



