Nerita. 



MOLLUSCA. 



91 



Spherical, depressed, smooth ; spire short, consisting of two 

 inflated volutions, their upper edges furnished with a concave, 

 transversely striated groove or band, with a blunted apex ; um- 

 bilicus large, circular, gradually expanding into the base of the 

 body. 



Found in the Gault at Folkstone, Kent. 



22. Natica ELEGANS_The Elegant Natica, pi. XXXIII.* 

 fig. 21. 



Natica elegans. Sowerby, Geo. Trans. IV. 2nd scries, p. 

 347, pi. 23, fig. 3. 



Oblong, smooth ; spire small, with four flat-sided volutions, 

 their upper edges a little rounded, ending in an acute point ; 

 aperture somewhat more than two-thirds the length of the 

 shell. 



Found in the Portland Stone, Vale of Wardour, South Wilt- 

 shire. 



23. Natica carinata. — The Keeled Natica, pi. XXXIII.* 

 fig. 22, 23. 



Natica carinata. Sowerby, Geo. Trans. IV. 2nd series, p. 

 343, pi. 18, fig. 8. 



Shell transversely ovate ; body very large, flattened above ; 

 spire small, with two volutions, placed obliquely to the base of 

 the shell, and obtuse at the point; body provided with five pro- 

 minent and rugged keels, which terminate on the margin of the 

 widely expanding outer lip, and forming a scolloped edge; aper- 

 ture very large, semilunar ; inner lip very broadly reflected on 

 the columella. 



Found in the Sands of Blackdown, Devonshire. 



24. Natica granosa. — The Granular Natica, pi. XXXIII.* 

 fig. 24, 25. 



Natica granosa. Sowerby, Geo. Trans. IV. 2nd series, p. 

 343, pi. 18, fig. 7. 



Subglobose ; body very large, much inflated, and covered 

 with numerous, regular, spiral, rounded ridges, which are cros- 

 sed by many longitudinal strisD, or lines of growth, producing 

 rounded granulations ; spire small, consisting of three well 

 rounded, rapidly diminishing volutions, ending in a sharp point; 

 aperture oblong, slightly twisted, contracted above, and orbicu- 

 lar below; outer lip much dilated; inner lip broad, with a large 

 open umbilicus behind it. 



Found in the Sands at Blackdown, Devonshire. 



Genus XLIV.— NERITA._ia;«arcA. 



Shell solid, generally thick, semiglobular, or obovate ; 

 spire very short ; base of the body for the most part flat- 

 tened beneath, but destitute of an umbiUcus ; aperture 

 semicircular; margin of the outer lip sharp, and crenu- 

 iated, or toothed on the inner side ; pillar lip generally 

 oblique, flattened, sharp on the margin, which lies ob- 

 lique to the axis of the shell, and for the most part den- 

 tated or crenated; a small prominence exists at the lower 

 extremity of the inner lip, between which and the inner 

 lip the small appendage to the operculum slides, as the 

 animal opens or closes the aperture for egress; moving 

 in the same manner as a door on its hinges, when the 

 animal protrudes its body ; operculum testaceous. 



Neuita costata. — The Ribbed Nerita, pi. XLIV. fig. 

 Sowerby, V. p. 94, pi. 463, fig. 5, 6. Fle- 



1. 

 1,2. 



Nerita costata. 

 ming, p. 31!i. 



Shell nearly globular; spire much depressed, consisting of 

 two volutions, with a canaliculate suture; whole surface covered 

 by nmnerous, thin, sharp, longitudinal ribs ; aperture ncarlv 

 orbicular, much expanded ; outer lip rather thickened ; pillar 

 somewhat produced, and obtuse, and nearly divided by a slight 

 sinus into two blunt teeth. 



Found in the Oolite at Anclifle. 



2. Nerita l^vigata. — The Smooth Nerita, pi. XLIV. 

 fig. 3, 4. 



Nerita Icevigata. Sowerby, III. p. 31, pi. 217, fig. 1. Fle- 

 ming, p. 318. 



Subglobose, smooth, glossy ; spire conical, consisting of two 

 slightly divided, flat-sided volutions ; body invested by a sub- 

 central, nearly obscure, transverse sulcus ; base convex ; aper- 

 ture sublunate, its width greater than its length ; outer lip 

 smooth-edged ; columella obscure. 



Found in the Oolite at Dnndry. 



3. Nebita minuta — The Minute Nerita, pi. XLIV. fig. 

 5, 6, 7. 



Nerita minuta. Sowerby, V. p. 93, pi. 463, fig. 3, 4. Fle- 

 ming, p. 318. 



Orbicular, smooth; spire obscure, much depressed, consisting 

 of one volution and a half; aperture oval; outer lip blunted; 

 pillar lip destitute of any appearance of teeth. Diameter not 

 an eighth of an inch. Fig. 7, natural size. 



Found in the Oolite at Ancliffc. 



4. Nekita aperta The Open Nerita, pi. XLIV. fig. 



8,9. 



Nerita aperta. Sowerby, V. p. 30, pi. 424, fig. 2, 3, 4. 

 Fleming, p. 318. 



Suborbicular, smooth, with acutely zigzag brown lines, which 

 are equal in thickness to the white intervals between them ; 

 spire depressed, with two volutions; aperture wide, semilunate; 

 outer lip much thickened, its edge sharp and even ; inner lip 

 broadly reflected on the columella, its inner edge obscurely cre- 

 nated, and furnished with one large tooth. 



Found in the London Clay at Cowell Bay, Isle of Wight. 



5. Nerita globosa The Globular Nerita, pi. XLIV. 



fig. 10, 11. 



Nerita glolosa. Sowerby, V. p. 29, pi. 424, fig. 1. Fle- 

 ming, p. 318. 



Suborbicular ; spire hardly elevated above the body, with two 

 volutions ; aperture somewhat orbicular, within which, near its 

 lower end, a lamclliform tooth ; outer lip thin, destitute of cre- 

 nulations; pillar lip narrowly reflected on the columella above, 

 but wider below, provided with one very obtuse tooth near its 

 upper end ; whole surface transversely sulcated. 



Found in the London Clay, Hampshire. 



6. Nerita spirata. — The Short-spired Nerita, pi. XLIV. 

 fig. 24, 25. 



Nerita spirata. Sowerby, V. p. 93, pi. 463, fig. 1, 2. Fle- 

 ming, p. 319. 



Subglobose, smooth ; spire very small, in proportion to the 

 size of the shell, consisting of two volutions, and with an 

 obscure canal round their base ; body extremely large, broadly 



