LIMN AID A. 105 
Susramity POMPHOLIGIN ZA. 
Shell depressed globular, spiral, the spire but slightly raised. 
Pompnotyx, 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. 
Buceal plate subcordiform ; lateral jaws absent; genitalia on 
the left side (in Limneza 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 eyes, but it is nearly or entirely absent in others. 
Like the next genus, the shell is dextral whilst the animal is 
sinistral. 
CHOANOMPHALUS, Gerstfeldt, 1859. 
Etym—Choanos, a funnel; omphalos, an umbilicus. 
Distr.—C. Maackt, Gerst. (ciii, 24). Lake Baikal. 
Shell dextral, nearly planorbiform, the spire being scarcely 
raised, widely 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. 
PaciLospirkaA, Mérch. Proposed tor 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.—Megasystropha, Lea. 
Distr.—C. Newberryi, 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, 1870. Shell thicker, with a smaller umbilicus, 
with strongly marked growth-ribs, and without revolving carinee 
(except when young). C. Binneyi, Meek (ciii, 26). Tertiary; 
Nevada. 
SuspramMity PLANORBINA. 
Shell spiral, the volutions in the same plane, so that the spire 
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