GASTEROPODA NUDIBRANCHIATA. 



351 



From the observations of Van Hasselt it seems that we must here arrange 



The Scarabes, Montf. 



The shell is oval, and the aperture contracted by large teeth projecting from both the coluraellar 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 obUque channels. Their 

 shell is oval or oblong ; the aperture of the shape of the Bulimus or Limnaeas ; the hp furnished with 

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

 like the Limnreus, 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.] We find only one in France, from the coast of the Mediterranean {Auricula myosotis, Drap.) The 

 male has two tentacula, and the eyes are at their bases. [Carychium, MuUer, answers so nearly to the description 

 of Auricula, that the genera ought probably to be conjoined. The tyi>ical 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. 



Fig. 1C3. — Auricula scarabeeus 



THE SECOND ORDER OF THE GASTEROPODES. 



THE NUDIBRANCHIATA.* 



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

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

 reversed position, the foot applied against the surface, and made concave hke 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 branchise 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- 

 Fig. i64.-i)oris cornuta 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 hver, sheds a peculiar secretion, that escapes outwards by a hole near the anus. The 

 species are numerous, and some of them of considerable size. We find them on the shores 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 se.xual organs, whose orifices 

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

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

 The branchiae of Polycera, Cuv., are like those of Doris, but simpler, and furnished with two mem- 



tentacula. 



'ille into 



• My first four orders are joined together l)y M. de Bla 

 what he calls a sub-class, and names Paracephatophora tnonoicti. Of 

 my Nudibranchiata he makes two orders : in the lirst {Cyctobranchi- 

 atir) he places the Dorides ; in the second {Pult/bratirhitilii) the 

 Tritoniie and its allies, which he divides into two families, according 



as they have two or four tentacula. 



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

 vol. of tlie ^nnah of Katuriil Hialory ; and Montagu has dcscril>cil 

 many British species in the Liuuctan Transactions. — Ko. 



