222 WEST AMERICAN SHELLS 
whorls separated by a deep suture. The last whorl 
has a narrow ledge below the suture. It is found 
in the Columbia near Wallula, and the Snake 
River near Weiser. 
Paludeéstrina longinqua, Gld., the Desert Palu- 
destrina, (Amnicola longinqua), is found fossil 
on the Colorado Desert, also living in various 
parts of Arizona, Utah and Nevada. The little 
shell is about an eighth of an inch long, a tenth of 
an inch wide, and is reckoned as being very 
variable. 
Paludéstrina stearnsiana, Pilsbry, Stearn’s 
Paludestrina, has a minute shell, less than 3mm. 
in length. It is thin, corneous, ovate, glossy, with 
a rather obtuse apex. It is found chiefly in small 
streams around Oakland, Cal. 
Paludéstrina (Tryonia) protea, Gld., the Vari- 
able Paludestrina. Innumerable specimens of this 
little shell are found on the Colorado Desert in a 
sub-fossil form, bleached white. The shell is slen- 
der, about 4mm. long, the whorls rounded and 
distinet, and the aperture small. 
Paludéstrina (Tryoma) clathrata, Stimp., the 
Trellised Paludestrina, greatly resembles the last 
species and is found in connection with it, but is 
easily recognized by the transverse ribs which 
run across its slender whorls. 
Pomatiopsis californica, Pils., the California 
Potamiopsis, is found around San Francisco and 
Oakland. The shell is turreted-conic, umbilicate, 
rather thin, chestnut-brown. The whorls are very 
convex, separated by deep sutures; length, 5mm. 
