NICANIA. 215 



3. Neeitista. Shell thin ; eolumellar lip septiform, edge 



denticulated ; generally a thick, dark coloured epidermis. 

 Fig. 324 to 326. 



4. Natica. Having an umbilicus behind the eolumellar lip, 



with a spiral callosity. Fig. 327, 328. 



5. Neeitopsis. Edge of the eolumellar lip with a deep 



notch. Fig. 331. 



6. PiLEOLUS. PateUiform ; apex central ; eolumellar lip sep- 



tiform, leaving the aperture small. Fig. 322. 



7. Janthiita. Columellar lip linear; aperture angulated. 



Fig. 333. 



NEEITELLA. Humph. 1797. Neeitina, Lamarck, 1822. 



NERITINA. Lamarck, 1822. Neeitblla, Humph. Fam. 

 Neritacea, Lam. — Bescr, Thin, semigloboae, obliquely oval, 

 smooth, flattish in front ; spire short, sometimes depressed, con- 

 sisting of few rapidly increasing whorls ; aperture semicircular ; 

 outer lip thin, sharp ; eolumellar Hp broad, flat, its inner edge 

 straight, denticulated ; operculum testaceous, semicircular, sub- 

 spiral, with an articulating process on the inner edge. — Obs. 

 This genus of fresh-water shells differs from Nerita in the 

 minuteness of the denticulation of the columeUar, as well as in 

 the characters mentioned in our observations upon the latter 

 genus. N. Spinosa, (Clithon, Montf.) fig. 352. IST. virginea, fig. 

 324. N. perversa. Lam. (Yelates, Montf.) fig. 326. The Mono- 

 graph, in PL 10 of the Thesaurus Conchyliorum, contains 116 

 species. Our Plate xv. fig. 324, 325. 



NEEITOPSIS. Gray. Fam. Neritacea, Jj^m.—Descr. Sub- 

 globose, thick, cancellated ; spire short, composed of few 

 rapidly increasing whorls ; aperture transverse, sub-orbicular; 

 outer lip thickened vrithin; columellar lip thick, rather flat, 

 with a large roimded notch in the centre of its inner edge.— 

 Obs. This genus most nearly resembles Nerita, from which it 

 differs in the peculiar notch of the columella, N. granosa. PI. 

 XV. fig. 331. 



NICANIA. Leach. Astaete, Sowerby. The same as Ceas- 

 siFA of Lamarck. 



