318 MOLLUSCA. PECTINIBRANCHIA. Nerita. 



NERITADjTC. 



* Marine. 

 Nerita. 

 Natica. 



•• Fluviaiile. 

 Neritina. 



Gen. LVII. NERITA.— Pillar-lip flat, entering the cavity, 

 entire behind. 



- 270. N. littoralis. — Whorls five, nearly smooth, the outer lip 



thin on the edge, thickened within. 



Nerita ex fusco-viridescens, List. An. Ang. 1G4, t. iii. f. 11, 12, 13. Conch, 

 t. Dcvii. £ 39-44 — N. litt. Linn. Syst. 1253. Mont. Test. Brit. 467. 

 — Common on sea rocks, covered with the tide. 



Length and breadth about three-quarters of an inch. Shell thick and 

 strong, variously coloured ; whorls increase rapidly, spire short, depressed, 

 the separating line small ; aperture semicircular, but the pillar is more round- 

 ed anteally, where it joins the outer lip, than is usual in the genus; hence 

 Lamarck has placed the shell in the genus Turbo (T. retusus. Hist. Vert. vii. 

 48.) ; a subperforation appears on the pillar. This shell is subject to consi- 

 derable variation in the shape, arising from the spire being more or less pro- 

 duced ; the body-whorl round or compressed, and the outer lip retrally join- 

 ing the upper or middle part of the whorl. 



271. N. Virginea, — Smooth, polished ; pillar-lip toothed. 



Nerita, List. Conch, t. Devi. f. 35. Turton's Conch. Diet. 127 — West 

 coast of Ireland. 



Breadth of those found bv Dr Turton hardly the eighth of an inch, pale, 

 ferruginous, with black zigzag lines running in various directions ; whorls lit- 

 tle raised, a black line round the junctions. 



EXTINCT SPECIES. 



1. N. lavigata. — Pointed, smooth; spire conical, with straight sides; base 

 convex Sower. Min. Conch, t. cexvii. f. i. — Inferior Oolite. 



2. N. sintwsa Obtuse, uneven ; spire short, with convex whorls ; aperture 



with a rounded sinus near the base, and an angular sinus near the middle. — 

 Soiver. Min. Conch, cexvii. f. 2 — Portland Oolite at Chilmarsh. 



3. N. globosa Subglobose, transversely sulcated ; spire apparent ; one tooth 



upon the inner lip ; outer lip plain within — Sower. Min. Conch, t. ccccxxiv. 

 ft 1.— London Clay. 



4. N. aperta Subhemispherical, smooth ; spire visible, depressed ; aper- 

 ture orbicular, expanded ; inner lip obscurely crenated, bearing one large 

 tooth Sower. Min. Conch, t. ccccxxiv. f. 2, 3, 4. — London Clay. 



5. N. minuta Hemispherical, smooth ; spire indistinct, aperture oval ; 



pillar-lip not toothed.—- Soiver. Min. Conch, t. cccclxiii. ft 3, 4. Oolite at An- 

 cliff. 



