manual of the mollusca. 



[Family Eissoid^] 



Includes Litiopa (p. 255), Eissoina (p. 256), Eissoa (p. 255), 

 and tlie following additional genera : — 



DLA.STOMA, Deshayes, 1864. 



Type, Melania costellata, Lamarck. 



Shell elongated, turreted ; wHorls "witii varices ; aperture very 

 oblique, semi-lunate, entire ; base sinuated, subangular ; pos- 

 terior angle acute, detacbed from tbe penultimate wborl; lip 

 tbin, curved ; columella concave, depressed, narrow. 



Fossil, 4 species. Eocene. Paris basin. 



Amphitbaxamus, p. Carpenter, 1865. 



Type, A. inclusus. "West Coast of ISTortb America. 



Shell like Bissoa, nucleus large; aperture witb a produced 

 lip, suddenly contracted in tbe adult. 



Tbis genus bears tbe same relation to Bissoa tbat Stoastoma 

 does to Helicina. 



Keilostoma, Desbayes, 1848. 



Type, Melania marginata, Lamk. 



Shell elongated, turriculated, regularly conical; generally 

 striated transversely. Aperture entire, sbort, effuse at tbe base, 

 angulated posteriorly ; columella sbort, callous ; tbe peri- 

 stome entire, tbe left lip broad and tbick, tbe rigbt broadly 

 m.argined. 



Fossil, Eocene, 6 species ; Paris basin. Belgium, England, 

 Punjaub. Cretaceous, 5 species ; India, Grosau. 



Pterostoma, Desbayes, 1864. 



\ Type, P. tuba. Eocene. Grignon, Paris. 



Shell elongated, turriculated ; peristome continuous, circular, 

 very dilated and margined ; columella very broad, expanded, 

 and continuous witb tbe peristome. 



ScALiOLA, Adams, 1860. 



Type, S. bella. 



Animal witb tbe rostrum elongated, cylindrical, annulated, 

 bifid at tbe end; tentacles filiform, eyes ■••''Qminent, black at 

 tbe outer base of tbe tentacles ; foot sbort, ovate, posteriorly 

 sub-acuminate; operculum corneous, ovate, subspiral; nucleus 

 subterminal. 

 3r 



