TRACHELIPODA. 85 



low, without an umbilicus ; aperture semiorbicular and entire ; 

 iiinerlip depressed, septiform, acute, and frequently dentated or 

 crenated on the inner edge of the lip ; outer lip obtuse, and of- 

 ten provided internally with teeth. 



Neriia peloronta. — The Monstrous Nerita. Plate XII. 

 fig. 13. Thick, transversely sulcated ; ash-coloured, or reddish, 

 yellow, with variously coloured bands ; inner lip with two cre- 

 nulations, outer lip with two deep notches near its internal upper 

 edge, and a bloody mark at the base of the inner teeth. One 

 inch long. Inhabits the seas of South America. 



Genus 57 — NERITOIDES.— iSrown. 



Generic Character. — Shell strong, thick, subrotund ; spire de- 

 pressed ; aperture nearly round ; lip almost continuous, having 

 a slight groove only at its junction with the body ; no umbilicus. 



Neritoides litoralis. — The Shore Neritoides. Plate XIII. 

 fig. 24. Smooth, covered with an olive-green, yellow, brown, 

 or other coloured epidermis, sometimes beautifully banded or 

 chequered beneath it ; inside generally purplish-brown ; body 

 very large ; spire very short and depressed. Five eighths of an 

 inch long. Inhabits the shores of Northern Europe. 



Genus 58 — NERITINA.— Zawjorc^. 



Generic Character. — Shell thin, semiglobose, or ovate, flat- 

 tened below ; without an umbilicus ; aperture semicircular ; in- 

 ner lip flattened, and reflected on the columella, sometimes 

 slightly crenated ; outer lip destitute of teeth or crenulations on 

 its internal face ; aperture provided with an operculum, having 

 a lateral point. 



Neritina fiuviatilis. — The Fresh -Water Neritina. Plate 

 XII. fig. 14. Shell small, oval ; back convex, smooth, white, 

 variously speckled with black, or dark brown ; spire inclined, 

 lateral ; lip slightly denticulate. One third of an inch long. 

 Inhabits the rivers and streams of Europe. 



Genus 59.— NAVICELL A.— ZamarcA. 



Generic Character. — Shell elliptical or oblong ; convex above, 

 H 



