50 MOLLUSCA. TRCHELIPODA. 



rounded, obtuse, diaphanous and extremely brittle ; aperture sub- 

 triangular, with a notch in the margin of the upper lip. 1 inch 

 long. Atlantic and Mediterranean seas Lister, pi. 572, fig. 24. 



FAMILY VI. NERITACEA. 



Shell fluviatile or marine, semiglobular or oval, without columel- 

 la, and the left margin edged and transverse ; an operculum. 



Gen. 55. NATICA, Lam. Nerita, Lin. 



Shell subglobose, umbilicated ; aperture entire, half rounded ; 

 inner lip oblique, not dentated, callous, the callosity modi- 

 fying the umbilicus, and sometimes covering it ; right margin 

 edged, smooth within ; an operculum. 



The Naticae are marine shells, the greater part smooth, ornamented with agreeable 

 colours, and all umbilicated, although their umbilicus is more or less obstructed, 

 concealed or covered by the callosity of the left margin, according to the species. They 

 differ from the Neritae by their umbilicus, by the pillar not being toothed, and by their 

 margin, which is always smooth interiorly. The opening is semicircular, and the 

 operculum is generally stony and solid The foot of the animal is shorter than the 

 shell ; its head is cylindrical and notched by a furrow ; and it has two long and 

 pointed tentacula, with the eyes sessile at their base. The species are numerous, and 

 the greater part live in the seas of warm climates. 



N. glaucina, Lam. Shell smooth, with a rather obtuse spire, glau- 

 cous, yellowish brown, or purplish flesh colour, with a row of darker 

 spots or streaks on the shoulder ; umbilicus partly closed by the 

 lip, which is gibbous and of two colours. 1 to 1 1 inch long. In- 

 habits European coasts. B Brown's Illust. pi. 43, fig. 1, 2, 8, 10. 



N. albumen, Lam. Shell depressed, convex, suborbicular, of a red- 

 dish yellow above, white beneath ; spire oblique, rounded; um- 

 bilicus somewhat heart-shaped and nearly filled up with a flat- 

 tened callosity- 1 1 inch in diameter. Inhabits Indian seas Rumph. 



Mus. pi. 22, fig. B. 



N. mamilla, Lam. Shell oval, ventricose, convex, depressed, with 

 the spire prominent, the umbilicus closed, and the aperture ovate; 

 colour snow white or yellowish brown, glabrous. 1^ inch long. 

 Inhabits West Indian seas Lister, pi. 571, fig. 22. " 



N. canrena, Lam. Shell umbilicated, smooth, and the spire slightly 

 mucronated ; umbilicus gibbous and bifid ; colour chestnut-brown, 

 with red and white bands, but varying extremely in the markings, 

 according to the age of the shell. 1| inch to 2 inches long. In- 

 habits Indian Ocean D'Argenv. pi. 7, fig- A. 



Gen. 56. NERITA, Lam. Lin. 



Shell solid, semiglobular, flattened below, not umbilicated ; aper- 

 ture entire, semicircular ; inner lip flattened, septiform, edg- 

 ed, often dentated, the teeth or crenulations on the interior 

 face of the outer lip. 



The Neritse are all marine shells, solid, thick, and agreeably coloured. They 

 are remarkable for their oblique columella, relative to the axis of the shell, which gives 

 the opening a semicircular form. The spire is scarcely elevated beyond the last 

 whorl, and the operculum is sometimes horny, sometimes calcareous, and semilunar. 



