230 LITTORINID^. 



with secondary forms : there are also some older fossils of somewhat 

 problematical position, Avhich may perhaps belong in the family. 



Section Littorina (sensii stricto.) 



Turbinate, thick, with moderate spire and acute apex. L. lit- 

 TOREA, Linn. 



Section Melaraphe, Muhlfeldt, 1828. 



Shell rather thin, conical, with pointed spire; surface with re- 

 volving sculpture, and usually variegated with brilliant colors. 

 Tropical and subtropical. L. scabra, Linn. 



Littorinopsis (Beck), Morch. 1876, is a synonym. 



Section Neritoides, Brown, 1827. 



Shell short, turbinate or subglobose, spire very short, with ob- 

 tuse apex; solid, inner lip much thickened and excavated. L. OB- 

 TUSATA, Linn. 



Neritrema, Recluz, is a synonym. 



Section Lamellilitorina, Try on. 



Whorls crossed by lamellfe, like Scalaria. L. albicans, Met- 

 calfe. 



Section L^vilitorina, Pfeffer, 1886. 



Chitinous, scarcely chalky, fragile, rimate; lip thin, sharp, the 

 extremities united by a thin callus ; epidermis smooth. 



L. CALiGiNosA, Gld. Antarctic Sea. 



Section Pellilitorina, Pfeffer, 1886, 



Thin, imperforate, brownish, Avith rounded hairy whorls, colum- 

 ellar callus weak, peristome thin, acute. L. setosa. Smith. 



Antarctic Sea. 

 Section Aquilonaria, Dall., 1886. 



Paludiniform, thin, membranous, imperforate, smooth, under a 

 rough shaggy epidermis. Operculum paucispiral, with a raised 

 subspiral rib on the inner side. 



Animal (PI. 40, fig. 73) much like Littorina, with entire sole, 

 tissues soft and gelatinous, with a profusion of tenacious mucus; 

 no jaw; phytophagous; mantle-edge plain, no opercular appen- 

 dages; oviparous. A. Turneri, Dall. 



Labrador, and Arctic Ocean, north of Bering's Strait, 



