105 



MONOaRAPH OF THE GENUS 



NERITA. 



Testa marina, plerumque solida, plus minusve rotunda; 

 spira plerumque subdepressa, raro exserta, nonnimquam 

 planulata ; apertura semirotunda, area columellari plerumque 

 oblique rectiuscula callosa, frequenter rugata, vel verrucosa, 

 margine plerumque dentato ; labio externo expanse, intus 

 calloso, tum plus minusve crenato, supra infraque nonnunquam 

 uni- vel bi-dentato. Operculo testaceo, semicirculari vix uni- 

 spirali per appendieem dentiformem ad columellam articulato. 

 — The Neritse, which are marine, may fairly be distinguished 

 from the Neritinse, which are mostly inhabitants of fresh water. 

 The former are generally more solid, more sculptured, and 

 more strongly toothed in the mouth. The latter are always 

 smooth, or nearly so, and the shelving columellar area is very 

 nearly if not entirely without teeth on the margin. The 

 operculum in both genera is articulated to the edge of the 

 columella by a small square projecting appendix. 



Species. 



1. POLiTA, f. 2, 3, Linnccus. — Solida polita fasciata et 

 varie picta, oblique ovata, area columellari crassa callosa, labio 

 externo crasso, expanse, columella rude dentata. — This solid, 

 polished, and variously painted shell is well known. 



2. ANTiQUATA, f. 4, 92, Recluz. — N. politce similis, magis 

 rotunda concentrice rugata, labio interne verrucoso, labio 

 externo intus crenato, marginibus internis aiu'antiis. — Differ- 

 ing from N. polita, being more or less concentrically wrinkled, 



