138 WEST AMERICAN SHELLS 
distinct. The surface is marked with many mic- 
roscopie spiral lines, which are crossed by rough- 
ened ridges. Variety ptychophora, A. D. Brown, 
is found in Idaho and eastern Oregon. ‘The shell 
is nearly smooth and is of a light horn-color but it 
has the regular markings and the broad white peri- 
stome of the typical specimens; diameter, 20mm. 
Polygyra columbiana, Lea, the Col- 
umbia Snail, Fig. 114, (Mesodon col- 
umbianus), is a species which extends SQ 
from Alaska southward into Califor- Fig. 114 
nia. Whorls six, umbilicus small, peristome re- 
flected, aperture ear-shaped. In some varieties, 
as shown in the cut, there is a small white tooth 
on the inner wall of the aperture. The figure is of 
the natural size. The shell is hght horn-colored 
and the epidermis on the upper whorls is set with 
short, stiff, microscopic hairs. Var. armigera, 
Aneey, is smaller, more globose and convex be- 
neath, and more beset with hairs, which are ar- 
ranged in very oblique rows. Var. labiosa, Gld., 
has a very circular aperture, and widely reflected 
peristome. 
Polygyra dévia, Gld., the Devious Snail, (Meso- 
don devius), is a species which lives in Oregon; it 
has also crossed the Cascade Mountains, and en- 
tered Idaho. The shell is horn-colored or brown, 
solid and six-whorled. The peristome is white, 
wide, and bent back at right angles to the wall of the 
aperture. There is a distinct white tooth on the 
inner wall of the aperture, and sometimes one or 
more waves on the peristome. ‘There are several 
