AIR-BREATHING SNAILS AND SLUGS 



289 



three-lobed, and the umbilicus is partly covered by 

 the lip. The shell is dark horn-colored, and the 

 diameter is half an inch. This species is especially 

 found in eastern Washington and Idaho. 



Polygyra loricata^ Gld., the Mailed Snail, 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 is low and 

 dome-shaped. Aperture irregular, with white tooth 

 on the columella and two thickened spots on the 

 outer lip; surface horn-colored. Found in California 

 near San Francisco, and also in the Sierras. 



Polygyra m ear ?2 s i i, Dall, 

 Mearns's Snail, is shown in Figure 

 278. This shell is of a pinkish- 

 brown color, and the details of its 

 structure are well brought out in 

 the three figures. Its diameter is 

 about half an inch. It is found in 

 Arizona and New Mexico. 



Vallonia pulchella^ Mull., the 

 Beautiful Vallonia, is a little mol- 

 lusk whose shell consists of four 

 rounded whorls arranged in a flat- 

 tened spiral form. The umbilicus 

 is large and open, the aperture 

 nearly circular, the peristome white, 

 reflected, and forming a nearly complete circle. 

 The shell is whitish, thin, and in our variety is usu- 

 ally marked by cross-ribs. Its diameter is barely an 

 eighth of an inch. This species is very widely dis- 

 tributed. A few years ago it suddenly appeared in 



Fig. 278, X 3 (*) 



