AIR-BREATHERS 139 
varieties which range from half an inch to a whole 
one in diameter. 
Polygyra mullani, Bland, Mullan’s Snail, was 
sometimes considered a small variety of the last 
species, but is now believed to be distinct. ‘The 
shell is shining, with a thin epidermis covered with 
minute spiral lines, and tubercles. The aperture 
is three-lobed, and the umbilicus is partly covered 
by the lip. Shell dark horn-colored, diameter half 
an inch. There are several varieties which will 
be noticed in the List. 
Polygyra loricata, Gld., the Mailed Snail, (‘Trio- 
dopsis loricata), has a little shell only a quarter of 
an inch in diameter, but its five and a half whorls 
are very distinct. The umbilicus is small but deep, 
and the spire low dome-shaped. Aperture irregu- 
lar, with white tooth on the columella and two 
thickened spots on the outer lp; surface horn- 
eolored. Found in California near San Francisco, 
and also in the Sierras. 
Polygyra 
chirica- 
huana, Dall, 
\ the Chirica- 
he uw ama 
Saale) as 
shown in a 
much ma g- 
nified form 
in Figure 115. The shell is depressed, thin, pol- 
ished, and of a dark brownish color. The lip is 
strongly reflected and the aperture is destitute of 
Fig. 115, x 2 (*) 
