History of British animals - University of Guam Marine Laboratory

318 MOLLUSCA. PECTINIBRANCHIA. Nerita.* Marine.NERITADjTC.••Nerita.Natica.Fluviaiile.Neritina.Gen. LVII. NERITA.— Pillar-lip flat, entering the cavity,entire behind.-270. N. littoralis.— Whorls five, nearly smooth, the outer lipthin 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 andstrong, variously coloured ;whorls increase rapidly, spire short, depressed,the separating line small ; aperture semicircular, but the pillaris more roundedanteally, where it joins the outer lip, than is usual in the genus; henceLamarck 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 considerablevariation in the shape, arising from the spire being more or less producedthe ; body-whorl round or compressed, and the outer lip retrally joiningthe 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 —Westcoast 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 littleraised, a black line round the junctions.EXTINCT SPECIES.1. N. lavigata.— Pointed, smooth; spire conical, with straight sides; baseconvex Sower. Min. Conch, t. cexvii. f. i.— Inferior Oolite.2. N. sintwsa Obtuse, uneven ; spire short, with convex whorls ; aperturewith 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 ; apertureorbicular, expanded;inner lip obscurely crenated, bearing one largetooth 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 Ancliff.