GASTEROPODA PECTJNIBRANCHIATA. 253 



tube, which is itself but an elongated fold of the mantle. The greater or less 

 length of the canal, when there is one, the size of the aperture, and the form 

 of the columella, furnish the grounds of its division into genera, which may be 

 variously grouped. 



CONUS, Linnceus. 



So called from the conical shape of the shell; the spire either perfectly flat, or 

 but slightly salient, forms the base of the cone, the apex being at the opposite 

 extremity; the aperture is narrow, rectilinear, or nearly so, extending from 

 one end to the other without enlargement or fold, either on its edge or on the 

 columella. The thinness of the animal is proportioned to the narrowness of 

 the aperture through which it issues; its tentacula and proboscis are highly 

 protractile; the eyes are placed on the outer side of the former, and near the 

 point; the operculum, situated obliquely on the hind part of the foot, is too 

 narrow and short to close the whole of the aperture. 



The shells of this genus, being usually ornamented with the most beautiful 

 colours, are very common in cabinets. The seas of Europe produce very few. 



CYPB^EA, Linnaeus. 



The spire projecting but little, and the aperture narrow and extending from 

 one extremity to the other ; but the shell, which is protuberant in the middle, 

 and almost equally narrowed at both ends, forms an oval, and the aperture in 

 the adult animal is transversely wrinkled on each side. The mantle is suffi- 

 ciently ample to fold over and envelope the shell, which at a certain age it 

 covers with a layer of another colour. The animal has moderate tentacula, 

 with the eyes at their external base, and a thin foot without an operculum. 



The colours of these shells, also, are extremely beautiful; they are common in 

 cabinets, though with very few exceptions they all inhabit the seas of tropical 

 countries. 



OVULA, Brugueir. 



The shell is oval, and the aperture narrow and long, as in Cypra?a,but without 

 plicae on the side next to the columella; the spire is concealed, and the two 

 ends of the aperture equally emarginated, or equally prolonged in a canal. The 

 animal has a broad foot; an extended mantle, which partly folds over the shell; 

 a moderate and obtuse snout; and two long tentacula, on which, at about the 

 third of their length, are the eyes. 



TEREBELLUM, Lamarck. 



An oblong shell, with a narrow aperture, without plicae or wrinkles, and in- 

 creasing regularly in width to the end opposite the spire, which is more or less 

 salient, according to the species. The animal is not known. The 



VOLUTA, Linnceus, 



Varies as to the form of the shell and that of the aperture, but is recognised 

 by the emargination without a canal which terminates it, and by the salient and 

 oblique plicae of the columella. From this genus Brugueir first separated the 



