34!6 SHELLS AND SHELL-FISH. 



Naticaria Sw.* Oval ; convex above ; 

 umbilicus small, open, placed very 

 near the top of the aperture ; inner 

 lip reflected, small, {fig. IO7.) 

 N. melanostoma. Mart. 189. f. 1926, 1927. 



cancellata Sw. lb. 189. f. 1939. 



bifasciata. GrifF. Cuv. 1. f. 2. 



Lacuna Turton. Turbinate ; thin ; spire very smaU, 

 of two whorls ; the general shape 

 is like Natica, but the base is 

 contracted ; umbilicus close to VWi 

 the top of the aperture, with a 

 groove running on the margin of the pillar, which is 

 oblique ; operculum horny ; aperture effuse, semicir- 

 cular, (fig. 108.) 



L. pallidula Twrtow. {fig. 108.) 



Leucotis Sw. Form of the shell intermediate between 

 Sigaretus and Lacuna ; but there is no pillar ; umbi- 

 licus large, pervious ; inner lip thin, slightly reflected 

 at the top j surface sculptured. 



Sigaretus caneellatus. Lam. Sys. vi. 2. p. 207. Chem. 

 165. f. 1596. 1597. 



SuB-FAM. ? NERITIN^. Nerits. 

 Globose ; spire very small ; pillar oblique ; inner lip 

 very broad, depressed, more or less flattened, and gene- 

 rally toothed j aperture semicircular. 



Nerita Linn. Shell solid ; inner lip toothed or gra- 

 nulated. 



N. peloronta. Mart. 192. f. polita. Mart. 193. f. 2002, 



1977—1981. 2003. 



Neritopsis Gray. Aperture sub-orbicular ; pillar lip 

 thickened above and below, with a wide notch in the 

 middle, f 



N. granosa. Sow. Man. f. 331. 



* These are probably aberrant species, connecting Sigaretus with Ma- 

 millariaj but, until the whole are better understood, I think it advisable 

 they should be kept distinct. 



+ Apparently related, by the shell, to Leucotis. 



