MOLLUSCA. 



It is probably analogous to an operculum, but does not exercise its functions, 

 being in a measure situated internally. The animal has long tentacula, at 

 whose external base are pedicles which support the eyes. They inhabit the 

 rivers of hot countries. In the 



CALYPTR.S:, Lamarck, 



We observe a conical shell, in the hollow of which is a little lamina that pro- 

 jects inwards, resembling the commencement of acolumella, and that interposes 

 itself between a fold of the abdominal sac. The branchia 1 are composed of a 

 range of numerous filaments, long and slender, like hairs. 



SIPHONARIA, Sorverby. 



The shell of the Siphonariae, which have recently been separated from the 

 Patella?, at the first glance seems very similar to a flattened Patella, with radia- 

 ting sulci ; but its margin projects rather more on the right side, and it is 

 excavated beneath by a slight furrow, which terminates at this prominence of 

 the margin, to which there is a corresponding lateral hole in the mantle, for 

 the introduction of water into the branchial cavity, placed on the back, that is 

 closed on every other point. The respiratory organ consists of a few small 

 lamella?, arranged in one transverse line on the roof of that cavity; the tenta- 

 cula seem to be wanting, the head being merely furnished with a narrow veil. 



SIGARETUS, Adanson. 



The shell is flattened, its aperture ample and round, and the spire very 

 moderate, its whorls rapidly enlarging and seen within, but concealed during 

 the life of the animal in the thickness of a fungous shield, which projects con- 

 siderably beyond it, as well as the foot, and which is the true mantle. Before 

 this mantle are an emargination and a semi-canal, which serve to conduct 

 water into the branchial cavity, and which form the passage to the following 

 family, but of which there are no impressions on the shell. The tentacula are 

 conical, with the eyes at their external base. 



CRYPTOSTOMA, Blainville. 



The shell, resembling that of a Sigaretus, with the head and abdomen, which 

 it covers, supported by a foot four times its size, cut square behind, and forming 

 before a fleshy oblong bundle that constitutes nearly one half of its mass. The 

 animal has a flat head, two tentacula and a broad branchial comb on the roof 

 of its dorsal cavity. 



FAMILY III. 

 BUCCINOIDA. 



THIS family has a spiral shell, in the aperture of which, near the extremity 

 of the columella, is an emargination or a canal for transmitting the siphon or 



