1915.] NATURAL SCIENCES OF PHILADELPHIA. 345: 
PUPILLIDA. 
Pupilla sonorana (Sterki). 
Station 11. Abundant on the summit of Big Hachet Mt. 
Bifidaria pellucidathordeacella (Pils.). 
Stations 3, 5,°8 and 11. 
A peculiar short cylindric form, having less convex whorls, less 
tapering spire and blunter summit, was taken at Stations 3 and 5. 
Bifidaria pilsbryana Sterki. 
Stations 8 and 11. 
Bifidaria ashmuni Sterki. 
Stations 3, 5, 8 and 11. 
VALLONIIDA. 
Vallonia sonorana n.sp. Fig. 5. 
The shell is very broadly, openly umbilicate, width of umbilicus 
contained about three times in the diameter of shell; whitish corneous. 
First 13 whorls smooth, corneous, glossy; following whorls with 
sculpture of rather delicate riblets about 38-40 on the last whorl, 
in fresh specimens bearing irregular cuticular extensions; the spaces 
between ribs delicately striate, the strie irregularly anastomosing. 
Whorls 32, strongly convex, rather slowly widening, separated by a 
Fig. 5.—Vallonia sonorana. <A, type; B, thick-lipped form. 
deep suture; the last whorl deeply descending close to the aperture. 
Aperture small, nearly circular, very oblique. The peristome is 
expanded and reflexed, slightly thickened within (in old specimens 
strongly thickened); the margins converge strongly and are con- 
nected by a very short parietal callus or are continuous, joined 
by a thin, slightly raised callus. The ample umbilicus is somewhat 
oblong. 
