GASTEROPODA NUDIBRANCIIIATA. 



351 



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



The Scarabes, Montf. 



The sliell is oval, and the aperture contraeted hy Large teeth projecting from both the columellar 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 misari'auged among 

 the Volutes. 



Auricula, Lam.. — 

 Differing from all precc<hng aquatic Pulmonea by having 

 their columella striated with large oldique channels. Their ■ n. i"o. 



shell is oval or oblong; the aperture of the shape of the Culimus or Liranasus ; the lip furnished with 

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

 like the Limnajus, 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, livin;^; on rocks hy 

 the soa-side.] We find only one in France, from the coast of the Mediterranean {Aiuicula myosotis, Drap.) Tlie 

 male has two tentacula, and the eyes are at tlieir bases. [C'arj/c/num, IVIuller, answers so nearly to the description 

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

 in shaded woods.] 



The INIelampes, i\Iontf. {Conovulns, Lam.), 

 Like tlie Auricula, have prominent plaits on the cohmrelia, hut their aperture has no varix, and its 

 inner li[) is linely striated : the shell has somewhat the shape of a cone, of which the spire makes the 

 base. They inhabit the rivers of the Antilles. 



THE SECOND ORDER OF THE GASTEROPODES. 



THE NUDIBRANCHIATA.* 



They have neither a shell nor pulmonary carity, but their branclii;c are exposed naked 

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

 reversed position, the foot a])plied against the surface, and made concave like a boat ; and 

 they assist their ]n-ogress by using the edges of the cloak and the tentacula as oars. 



The Doris, Cuv., — 

 Llave the anus in the posterior part of the hack, and the brand. ia; are arranged in a circle round the 

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

 gether a sort of flowc)'. The mouth is a small proboscis, situated 

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

 conical tentacula. There arc other t\\'o tentacula, of a conoid figure, 

 [and lamellated structure,] whicli issue from the sujierior and ante- 

 j.il:. ii;i — o..ris c innitii rior part of thc cloak. Tiie organs of generation have tlieir orifices 



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

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

 species are numerous, and some of them of considerable size. We find tlieni on the shores of eveiy 

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



'I'lie Oncliidores, Blainv., only differ from the Doris in the wider sepnration of their sexual organs, vhosc orifices 

 communicate by a farrow drawn alonf?; the ri^ht side, as in the Onchidia. The Plocamoceres, Leuckard, have all 

 tlu' characters of Onchidores, and moreover the anterior edfre of tlieir cloak is adorned with numerous branched 

 tciit:iri|ia. The branchiffi of Po/y""''") Cuv., are like those of Doris, but simpler, and furnished with two mem- 



• Mv r.r>t Intir onU-rs nr^' j.-iiiiL^ri louu-ther t>7 M. de Dlalnville i 

 lat liL- P.M-i n siLl,-i la^;, ;Mid iianic-s Pararrj/hnluphdra miy7inii;a. 

 ,- NudiltrnfLCliirttti liu ninliea two orders : in the first {Cj/chibrrini 

 ■i\ lie places the Derides; in the seeond [Ptili/brinirhiijt'^) 

 iloiii;e and its allies, which he divides into two latiiilies, accord 



ts thej" have two or four tentaenla. 



t The Scottish species are deserihed by Dr. Johnston in the Ist 

 vol. of the ,;»»«/,> „f X.ituT.il Hiatary : and Montnijn has dcscrihed 

 nany British species in the L'mnaan Truuaacliuni. — h"3. 



