LiMN-5;iD^. ip.5 



Subfamily POMPHOLIGIN^. 

 Shell depressed globular, spiral, the spire but slightly raised. 



PoMPHOLYX, Lea, 1856. 



Distr. — California. P. effusa^ Lea (ciii, 23). 



Shell dextral, rotund-gibbous, reflexed beneath, flattened above, 

 not umbilicated ; spire convexly depressed ; aperture very large, 

 subcircular, expanded ; outer lip acute, inner lip thickened and 

 slightly flattened. 



Buccal plate subcordiform ; lateral jaws absent ; genitalia on 

 the left side (in Limnaea on the right) ; tentacles stout, cylin- 

 drical, slightly globose at the tips ; eyes, sessile on the front of 

 the head near the inner bases of the tentacles. - 



In some individuals there is an aggregation of pigment-cells 

 near the tips of the tentacles, which has been taken for a second 

 pair of ej^es, but it is nearl}^ or entirely absent in othei'S. 



Like the next genus, the shell is dextral whilst the animal is 

 sinistral. 



Choanomphalus, Gerstfeldt, 1859. 



Etym — Choanos, a funnel; omphalos, an umbilicus. 



Distr. — G. Maacki, Gerst. (ciii, 24). Lake Baikal. 



Shell dextral, nearly planorbiform, the spire being scarcely 

 raised, widelj^ umbilicated ; aperture small, rounded, the extrem- 

 ities of the simple peristome united by a thin parietal callus. . 



Animal resembling Planorbis in its tentacles, jaw and den- 

 tition ; genital, respiratory and anal orifices on the left side. 



PffiCiLOSPiRA, Morch. Proposed for Planorbis multiformis, 

 Zieten, a miocene fossil of Steinheim, remarkable for poly- 

 morphism, and presenting all stages of form between discoidal 

 and conical, the last whorl in contact or reflected. 



Carinifex, Binney, 1865. 



Syn. — Megas3^stropha, Lea. 



Distr. — C. Newherryi, Lea (ciii, 25). California. 



Shell dextral, spiral, inflated, angular, horn-colored ; .spire 

 elevated, terraced; last whorl very large, broad above, very 

 rapidly attenuated below ; umbilicus funnel-shaped ; aperture 

 triangular, broad above, narrow below ; inner lip slightly thick- 

 ened ; outer lip thin, acute, angular above, flexuose. 



VORTICIFEX, Meek, 18T0. Shell thicker, with a smaller umbilicus, 

 with strongly marked growth-ribs, and without revolving carijQse 

 (except when young). C. Binneyi, Meek (ciii, 26). Tertiary; 

 Nevada. 



Subfamily PLANORBINJE. 



Shell spiral, the volutions in the same plane, so that the spire 



