MANUAL OF THE MOLLUSCA. 



Animal unknown ; habit subterranean. 



Shell similar to that of Achatina acicula, but the columella is 

 not truncated, and the outer lip is thickened. 



Xanthonyx, Crosse and Fischer, 1867. 



Type, Vitrina Sumichrasti, Brot., Mexico. 



Animal elongated, too large for complete retraction into the 

 shell; jaw like that of Avion; lingual dentition consisting of a 

 series of uniform teeth, with a broad and subcniadrangular base ; 

 the median tooth with a large central cusp and denticle on each 

 side ; the laterals are bicuspid, the internal cusp long, the 

 external short ?.nd obtuse, sometimes accompanied with the 

 rudiment of a third ; pulmonary orifice near the middle. 



Shell imperforated, very thin, transparent, subdepressed, 

 intermediate in form between Vitrina and Simpulopsis. 



Distribution, 3 species. Mexico. 



Family II. — Limacedje.* 

 Hyaximax, H. and A. Adams. 



Type, Limax perlucidus, Quoy. 



Animal limaciform, mantle large, shield-shaped ; pulmonary 

 orifice medial and marginal ; foot attenuated behind, no mucus 

 gland, separated below from the head by a distinct groove; 

 jaw analogous to that of Zonites with the support of Succinea ; 

 lingual dentition with a tricuspid median plate, laterals with a 

 large cusp, supporting two or three denticles. 



Shell internal, rounded, thin, and slightly arched above. 



Distribution, 2 species. Bourbon, Mauritius. 



Krynickia, Blainville, 1839. 



Dedicated to the naturalist Krynicki. 



Type, Limax megaspidus, Blainville. 



Animal limaciform, but the anterior part of the mantle is free 

 and detached from the body as far as the pulmonary orifice, 

 which is situated far back. 



Shell internal, flat, lamellose, elliptical, with no spiral 

 nucleus. 



Distribution, 8 species. Crimea, Caucasus, North America 

 ( 1 ) . Central America ( 1 ) . 



Philomycus, Eafinesque (p. 29C0. 



Type, Limax Carolmensis, xjosc. 



* See p. 295. 



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