ARIONIDA. 85 
simple; mantle anterior, close to head, concealing a shell-plate ; 
longitudinal furrows above the margin of the foot? a caudal 
mucous pore; a distinct locomotive ‘disk ; external respiratory 
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 system? 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 caudal 
mucous pore; a distinct locomotive disk; external respiratory and 
anal orifices on the right posterior margin of the mantle ; orifice 
of the combined genital system behind and below the right eye- 
peduncle. 
Internal shell small, oval, flat, with posterior nucleus and con- 
centric strive. 
Jaw with numerous ribs. Lingual membrane with tricuspid 
centrals, bicuspid laterals, and quadrate marginals. 
Propuysaon, Bland and Binney, 1873. 
Distr.—1 sp. Pacific coast of United States. P. Hemphilli, 
Binney 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. 
