NERITACEA. 201 



acute, consisting of few rounded whorls ; last whorl large, but 

 contracted near the aperture ; aperture small, oblique, rounded 

 anteriorly ; peritreme continuous, thin ; operculum spiral, horny, 

 with few volutions. — Obs. The distinguishing character of this 

 genus is the contraction of the last whorl near the aperture, in 

 which respect it is nearly resembled by the shell called Cyclostoma 

 lucidum. Two recent and one fossil species, all very minute, are 

 described by Sowerby in Loudon's Magazine of Natural History, 

 New Series. Fig. 305. 



NERINEA. Defr. Fam. Canalifera, Lam. — Bescr. Turrited, oblong, 

 sub-canaliculated, consisting of numerous whorls ; aperture with 

 a strong fold on the columella, one on the outer lip, and one on 

 the inner lip at the edge of the body whorl.— Obs. This genus is 

 only found in a fossil state usually in the Oolitic beds, it is not 

 resembled by any other ; the strong, prominent folds on the three 

 upper angles of the subquadrate aperture present a singular 

 appearance in a section. One species has been named N. Hiero- 

 glyphus. We give N. Goodhallii, fig. 374. 



NERITA. Auct. Fam. Neritacea, Lam. Hemicyclostomata, Bl. — 

 Bescr. Smooth or ribbed, semiglobose; spire short, sometimes flat, 

 consisting of few volutions ; aperture large, semilunar ; outer 

 lip thick, entire ; inner lip thickened, dentated at the edge, 

 spread over the body whorl, forming a flattened disc ; operculum 

 shelly, spiral, with an appendage by which it is locked under the 

 sharp edge of the columella. — Obs These marine shells are known 

 from Neritina by the thickness of the shell and the want of the 

 thick, horny, dark coloured epidermis ; from Natica by the flat 

 area produced by the spreading of the thickened columellar lip. 

 N. Peloronta, fig. 330. N. polita, fig. 329. 



NERITACEA. Lam. A family of the first order of Trachelipoda, 

 Lam. containing the following genera : 



1. Navicella. Apex terminal, not spiral ; inner lip septiform. 



Fig. 323. 



2. Nerita. Columellar lip septiform, edge with distinct teeth ; 



shell thick. Fig. 330. 



