Order 2. 



GASTEROPODA NUDIBRANCHIATA. 



343 



From the observations of Van Hasselt it seems that we must here ai'range 



The Scarabes, Montf. 



The shell is oval, and the aperture contracted by large teeth projecting from both the colaraellar side 

 as well as the outer lip : this lip is swollen, and as the 

 animal re-makes it after every half-whorl, the shell is most 

 protuberant on two opposite lines, and has a flattened 

 aspect. The animals live on aquatic plants in the Indian 

 Archipelago. 



The two genera which follow were misarranged among 



the Volutes. 



Auricula, Lam., — 



Differing from all preceding aquatic Pulmonea by having 



their columella striated with large oblique channels. Their 



shell is oval or oblong ; the aperture of the shape of the Bulimus or Limnseus ; the lip furnished with 



a varix. Several species are of considerable bulk ; but it is not ascertained if they live in marshes, 



like the Limnaius, or merely upon their margins, after the manner of the Succinea. 



[One species, according; to Lesson, lives in fresh water ; the others appear to be terrestrial, living- on rocks by 

 the sea-side.] AVe find only one in France, from the coast of the Mediterranean (Auricula myosolis, Drap.) The 

 male has two tentacula, and the eyes are at tlieir bases. [Cari/chium, Muller, answers so nearly to the description 

 of Auricula, that the genera ought probably to be conjoined. The typical species (C minimum) lives under leaves 

 in shaded woods.] 



The Melampes, Montf. {Conovulus, Lam.), 

 Like the Auricula, have prominent plaits on the columella, but their aperture has no varix, and its 

 inner lip is finely striated : the shell has somewhat the shape of a cone, of which the spire makes the 

 base. They inhabit the rivers of the Antilles. 



Fijf. 163. — Axiricula scarabffius 



THE SECOND ORDER OF THE GASTEROPODES. 



THE NUDIBRANCHIATA.* 



They have neither a shell nor pulmonary cavity, but their branchiae are exposed naked 

 upon some part of the back : they are all hermaphroditical and m.arine : they often swim in a 

 reversed position, the foot ajjplied against the surface, and made concave like a boat ; and 

 they assist their progress by using the edges of the cloak and the tentacula as oars. 



The Doris, Cuv., — 

 Have the anus in the posterior part of the back, and the branchiae are arranged in a circle round the 



anus ; and as each resembles a little arbuscule, they constitute alto- 

 gether a sort of flower. The mouth is a small proboscis, situated 

 under the anterior edge of the cloak, and is furnished with two small 

 conical tentacula. There are other two tentacula, of a conoid figure, 

 [and lamellated structure,] which issue from the superior and ante- 

 iii;. iii^— ii'Ti^ ■^'riiuta rior part of the cloak. The organs of generation have their orifices 



near to each other, under its right margin. The stomach is membranous. A gland, intimately inter- 

 laced with the liVer, sheds a peculiar secretion, that escapes outwards by a hole near the anus. Tlie 

 species are numerous, and some of them of considerable size. We find them on the sliores of every 

 sea.f Their spawn is shed in the form of a gelatinous ribbon, on rocks and sea-weeds, &c. 



The Onchidores, Blainv., only differ from the Doris in the wider separation of their sexual organs, whose orifices 

 communicate by a furrow drawn along the right side, as in the Onchidia. The Plocamoceres, Leuckard, have all 

 the characters of Onchidores, and moreover the anterior edge of tlieir cloak is adorned with numerous branched 

 tentacula. The branchiae of Poli/cera, Cuv., are like those of Doris, but simpler, and furnished with two mem- 



• My first four orders are joined together by M. de Blainvill* into 

 wliat he calls a sub-class, and names Pararephnluphora moiwica. Of 

 my Nudibranchjata he makes two orders : in the first {Cr/rlobrtinchi- 

 ala) he places the Dorides ; in the second {Pult/l/rririrhialn) the 

 Tiiloniu? and its allies, which he divides into two families, according 



as they have two or four tentacula. 



t The Scottish species are described by Dr. Johnston in the 1st 

 vol. of ilie Annals of Nfittirul History ; and Montatju has described ' 

 many British species in the Linnaan Transtictiont.-^Kv. 



