ARIONID^. 85 



simple ; mantle anterior, close to head, concealing a sliell-plate ; 

 longitudinal furrows above the margin of the foot ? a candal 

 mucous pore ; a distinct locomotive disk ; external respii'atory 

 and anal orifices on the right far anterior margin of mantle ; 

 orifice of combined genital system behind and below right eye- 

 peduncle. 



Shell-plate calcareous, flat, small, internal, ovate. 



Jaw ribbed. Lingual membrane with tricuspid centrals, 

 bicuspid laterals, quadrate marginals. 



LETOURNEUXiA, Bourg., 1866. Animal limaciform, subcylin- 

 drical, scarcely attenuated behind ; tentacles simple ; mantle 

 small, anterior, concealing a shell-plate ; no longitudinal furrows 

 above the margin of the foot, and no caudal mucous pore ; no 

 distinct locomotive disk; external respiratory and anal orifices 

 on the right anterior margin of the mantle ; orifice of the com- 

 bined genital sj^stem? Shell-plate internal, calcareous, suboval, 

 flat. Jaw ribbed. Lingual membrane ? There is a peculiar 

 overhanging process to the side of the body, near the tail. 

 Algiers. G. Numidicus, Bourg. 



Anadenus, Heynemann, 1863. 



Distr. — 2 sp. Himalaya Mountains. A. giganteus, Heynem. 



Animal limaciform, subcylindrical, tapering behind ; tentacles 

 simple ; mantle anterior, concealing an interior shell-plate ; no 

 longitudinal furrows above the margin of the foot, and no cavidal 

 mucous pore ; a distinct locomotive disk; external respiratory and 

 anal orifices on the right posterior margin of the mantle ; oi-ifice 

 of the combined genital s^'stem behind and below the right eye- 

 peduncle. 



Internal shell small, oval, flat, with posterior nucleus and con- 

 centric strise. 



Jaw with numerous ribs. Lingual membrane with tricuspid 

 centrals, bicuspid laterals, and quadrate mai'ginals. 



Prophysaon, Bland and Binney, 1813. 



Distr. — 1 sp. Pacific coast of United States. F. Eemphilli, 

 Binnej^ and Bland. 



Animal limaciform, subcylindrical, tapering behind ; tentacles 

 simple ; mantle small, anterior, concealing a shell-plate ; no longi- 

 tudinal furrows above the margin of the foot, and no caudal 

 mucous pore ; no distinct locomotive disk ; external respiratory 

 and anal orifices on the right anterior margin of the mantle ; 

 orifice of combined genital system behind and below the right 

 peduncle. 



Internal shell-plate thick, small, flat, longer than wide. 



Jaw ribbed. 



