294 NERITID^. 



foot oblong, triangular. Lingual dentition similar to the Turbi- 

 nidse. Teeth 7 ; uncini very numerous (xii, 44, 45). 



Nerita, Linn. 



Etym. — Nerites, a sea-snail, from Nereis. 



Distr. — Over 200 sp. Nearly all warm seas. West Indies, 

 Red Sea, Zanzibar, Philippines, Australia, Central Pacific, West 

 America. Many of the American species dwell in the streams ; 

 one species at the Philippines sometimes climbs up trees. 



Fossil, 60 sp. Lias — ; Britain, etc. The palaeozoic Nerites 

 are referred by d'Orbigny to Turbo, Natica, etc. 



N. polita, Linn. N. peleronta, Linn. N. histrio, Linn. N. 

 undata, Linn. (Ixxviii, 51-54). 



Shell thick, smooth or spirally grooved ; epidermis horny ; 

 outer lip thickened and sometimes denticulated within ; colu- 

 mella broad and flat, with its inner edge straight and toothed. 

 Operculum shelly. 



Animal with the mantle-margin festooned. Living on rocks 

 and stones, and said to be most active during the night, when 

 they roam about, feeding on the algse ; their eggs are ovate, 

 covered with a horny skin, and attached to other shells. 



PELERONTA, Okcu. (Pila, Klciu. Ritena and Tenare, Gray.) 

 Inner lip rugose, outer lip dentate within. N. Deshayesii^^eclnz 

 (Ixxviii, 55). 



THELIOSTYLA, Morch. (Natcrc, Gray. Dontostoma, Klein.) 

 Inner lipgranulatedortuberculated. N. exuvia^Ijinn. (Ixxviii, 56). 



DEIANIRA, Stolicz. Shell subgiobose, consisting of few whorls, 

 the last of which is the largest, often carinated posteriorly ; 

 aperture large, semilunar; inner lip thick with three folds, the 

 posterior one of which is the strongest. Operculum broadly 

 oval, calcareous, with a tooth on the inner edge, and a groove 

 corresponding to the strong posterior fold of the inner lip. Cret., 

 fresh and brackish water deposits of the N. Eastern Alps. N. 

 bicarinata^ Stol. (Ixxviii, 5*7, 58). 



LissocHiLUS, Petho., 1882. Outer lip sharp, not thickened nor 

 dentate within, inner lip not dentate. Triassic and Jurassic. 

 N. sigaretina, Buv. 



OTOSTOMA, d'Arch., 1859. (? Lyosoma, White.) Shell thick, 

 globose ; upper part of body-whorl with somewhat curved folds 

 and very fine spiral lines ; inner lip callously thickened, toothed; 

 outer lip obliquely truncate, not thickened within: N. ru'gosa^ 

 Hoeningh. Cretaceous. 



Deshayesia, Raulin, 1844. 



Etym. — Dedicated to M. Deshayes, author of "Description des 

 Animaux sans Yertebres dans le bassin de Paris," etc. 



Sy7i. — Naticella, Grateloup (non Miinster). Oncochilus, Petho., 

 1882. 



