Orbtzr C. 



GASTEROPODA PECTINIBEANCHIATA. 



355 



an oval ; and its aperture iu the adult auinial is transversely toothed on each side. The cloak is suffi- 

 ciently ample to fold over and envelope the 

 shell, which, at a certain age, it covers with a 



A,,. 



Fig. 17A.— Cfpraea exanthema. 



layer of shell of another colour ; and from this 

 circumstance, joined to the change which the 

 aperture undergoes, the full-grown shell may he 

 mistaken for another species. The animal has 

 moderate tentacula, with the eyes at their ex- 

 ternal hases, and a thin foot without an oper- 

 culum. 



The colours of the shells are very beautiful, and 

 many species are found in our cabinets, though, with 

 very few exceptions, they all inhabit the seas of tro- 

 pical countries. [Bi-U2:uieres was of opinion that the 

 animal of the Cypraja, before it arrived at its complete 

 growth, abandons its shell several times, to form 

 another more fitted to its dimensions. This opinion 

 is now relinquished.] 



The Ovul^, Brug. — 

 Have an oval shell, with a narrow, lengthened 

 aperture, as in Cypraea, but without teeth on the columellar side ; the spire is concealed, and the two 

 ends of the aperture are nearly equally emarginated, or equally prolonged into a canal. Linnaeus con- 

 founded them with Bulla, from which they were properly separated by Bruguieres. Their snail has a 

 broad foot, an expanded cloak, which partly folds over the shell, a moderate and obtuse snout, and two 

 long tentacula, on which we find the eyes at about the third of their length on the outside. Montfort 

 restricts the name Ovula to such shells as are transversely denticulated on the outer hp ; and he names 

 those iu which the two ends of the aperture are prolonged into a canal, and the outer lip is plain, the 

 Volva. When this lip is also plain, without a prolongation on each side, he calls the genus Calpurna. 



Terebellum, Lam. — 

 Has an oblong [or subcylindrical] shell, with a narrow aperture, without plaits or gi'ooves, and 

 increasing regularly in width to the end opposite the spire, which is more or less salient, according to 

 the species. The animal is not known. [On account of its hidden spire, Montfort separates the 

 species named Convolutum, by Lamarck, to form his genus Seraphs, which seems to be unnecessary.] 



The Volutes {Valuta, Linn.) — 

 Vary in the figure of the shell and of the aperture, but are recognized by the emargination without a 

 canal which terminates it, and by the oblique plaits of the columella. 



Bruguieres first separated from them the Oliva, so named from the oblong or elliptical form of the shell, whose 

 mouth is straight, long, and sinuated opposite tothe short spine, and the plaits of the columella are numerous and 

 similar to striie. The whorls are separated from each other by a narrow groove. These shells do not yield in beauty 

 to the Cowries. Their animal has a large foot, the anterior part of which (in advance of the head) is .separated by 

 nn indentation on each side : the tentacula are slender, and the eyes are on their side near the middle of their 

 length. The proboscis, the siphon, and penis are tolerably long : they have no operculum. MM. Quoy and 

 Gaymard have observed at the posterior part of the foot an appendage, which is laid in the furrow of the whorls. 



The remaining species of the Volutes have been subdivided into five genera by M. de Lamarck. The Volcaria 

 Ecarly resemble Oliva in their oblong or cylindrical form ; but their aperture is narrow, and its anterior margin 

 rises even above the spire, which is extremely short. There are one or several plaits on the columella, ."'^eir 

 polish and whiteness has induced the natives of some countries to string them into necklaces. There is a small 

 fossil species in the environs of Paris. [According to Sowerby, Volvaria is entirely a fossil genus, of which two 

 species are found in the environs of Paris, and one in the London clay at Hordwell.] Valuta, Lam., has an ample 

 aperture, and a columella marked with some large plaits, of which the inferior is the strongest. Their spire varies 

 much in its prominence. Some (Cymhium, Montf. ; Cymha, Sowerb.) have the last whorl ventricose : their animal 

 has a large, thick, fleshy foot, without an operculum ; and over the head a veil, at the sides of which the tentacula 

 issue. The eyes are seated on this veil, exterior to the tentacula. The proboscis is of considerable length, and the 

 syphon has an appendage on each side of its base. The shells attain a great size, and several are very beautiful. 

 [" The shells are ventricose, light, and buoyant, floating when placed upon their backs on water, and having when 

 »o placed a boat-like appearance. Their apex is rude, and without regularity of shape. They are sombre, and, 

 tor the most part, uniform iu colour. They are covered with a smooth brown epidermis, which is, again, more or 



