362 



MOLLUSCA. 



duce the water to tlie branchial cavity placea upon the back, and closed in every other place. The 

 respiratory organ consists in a few small leaflets, attached in a ti-ansverse line to the bottom of that 

 cavity. The animal appears to have no tentacula, but only a narrow veil upon the head. There are 

 species in which the shell shows no appeai-ance of the groove, and would perfectly resemble a Patella 

 were it not that its vertex is turned backwards. [We must observe, says Rang, that we have seen 

 young Patelte to have the character of Siphonaria, and to preserve traces of it at a more advanced age: 

 it is only then provisionally that we adopt this genus, and assign it a place among the Inferobranchiata.] 



SiGARETUs, Adans. 

 The shell is flattened, with an ample round aperture, and an inconsiderable spire, whose whorls enlarge 

 very rapidly, and are visible on the inside. It is hidden during life in the fungous shield of the animal, 

 which projects considerably beyond it, as well as the foot, and is the true mantle. We observe in front 

 of this mantle an emargination and a semi-canal, the use of which is to conduct water into the branchial 

 cavity, but which leave no impressions on the shell. The structure indicates a transition to the following 

 family. The tentacula are conical, with the eyes at their exterior base : the penis of the male is very 

 large. 



There are species on our own coasts. [This remark is erroneous, unless we consider Cuvier's Sigaretus the 

 same as Pleurobranchus. See some remarks on the confusion in the nomenclature of this genus by Mr. Gray, in 

 the Zool. Journ. i. p. 428.] 



Coriocella, Blainv., is a Sigaretus with a horny and almost membranous shell, like that of Aplysia. 



The Cryptostoma, Blainv. — 

 Has a shell very similar to Sigaretus, supported, with the head and abdomen (which it covers), on a foot 

 four times its size, cut square behind, and which produces in front a fleshy oblong part that constitutes 

 nearly one half of its mass. The animal has a flat head, two tentacula, a broad branchial comb on the 

 roof of its dorsal cavity, and the penis under the right tentaculum, but I have not seen any emargination 

 in the cloak. 



THE THIRD FAMILY OF THE PECTINIBRANCHIATA,— 

 The BucciNOiDES,* — 

 Have a spiral shell, the mouth of which has, near the end of the columella, a sinus or canal, for the 

 passage of the siphon or tube formed by an elongated fold of the cloak. The greater or less length of 

 this canal when it exists, the greater or less width of the aperture, and the various forms of the 

 columella, afford characters for a division of the family into genera, which can be grouped in various 

 ways. 



The Cones {Conus, Linn.) — 



Are so named from the conical figure of their shells. The spire, 

 either flat or sUghtly raised, forms the base of the cone, whose 

 apex is at the opposite extremity : the aperture is narrow^ 

 rectilinear, or nearly so, extended from one end to the other, 

 without protuberance or fold, either on the columella or the 

 margin. The animal is of a thinness proportioned to the aper- 

 ture through which it issues : its tentacula and proboscis are 

 much elongated, and we find the eyes near the apex of the 

 former, on the outside : the operculum, seated obliquely on the 

 hinder part of the foot, is narrow, and too short to close the 

 mouth of the shell. 

 The shells of this genus are in general beautifully coloured, whence 

 Fiji'. 175.— Tonus Eeiieraiis. jt happens that they crowd our cabinets. Our seas produce only a 



very few species, [of which there is a full enumeration in Lamarck's Histoire naturclle des Animaux sans veriebres.'] 



The Cowries (Cypresa, Linn.) — 

 Have also a [concealed or] very short spire, and a narrow aperture extending from one end to the 

 other ; but the shell, which is ventricose in the middle, and almost equally narrowed at both ends, forms 



* Coequal with the Faracephalaphora dioica siphonobrauchiata Qi 



t M. de Blainville unites in one family, n^aaeA Angyostomn, the 

 C0UU6, Cypraa, Ovula, Tcrebellum, and Voluta. In pl.icing; here the 



genera with a narrow ajierture, we do not intend to say that they i 

 nearest in affinity to the preceding family ; but we place them ti 

 because they exhibit the characters of the siphouifcrous tribes in I 

 most distinct manner. 



