1906.] NATURAL SCIENCES OF PHILADELPHIA. 151 
Vitrea hammonis (Strém). 
Drift of the Pecos river at Pecos, New Mexico (Cockerell). The 
specimens scarely show a trace of spiral lines. The species is unknown 
in the Austroriparian and Lower Sonoran zones. 
Vitrea dalliana roemeri n. subsp. Fig. 8. 
Shell openly umbilicate, the width of umbilicus contained about 
43 times in the diameter of the shell, pale whitish-corneous, in general 
shape resembling V. dalliana, V. wheatley: and V. petrophila. Sculp- 
ture of very close and regular radial grooves, on the last whorl of large 
specimens becoming crowded and less regular, giving a striate appear- 
ance. The flat intervals between the grooves show no spiral striz. 
The base is nearly smooth. Whorls 43, but slightly convex, slowly 
widening, the last about double the width of the preceding. Suture 
scarcely impressed, translucent-margined below. Base convex. Aper- 
ture lunate, slightly oblique; the insertions of the peristome are distant. 
Alt. 2, diam. 4 mm.; umbilicus .85 mm.; aperture 1.7 x 1.65 mm. 
Fig. 8.—Vitrea dalliana roemert. 
Sinking Spring creek, near San Marcos, Hays county, Texas. Types 
No. 91,318, A. N. 8. Phila., collected by Pilsbry and Ferriss, 1903. 
Also taken in several places around New Braunfels, Comal county; in 
the drift débris of the Hondo river, two miles north of Hondo, Medina 
county; in drift of the Rio San Filipe near Del Rio, and of the Devil’s 
river, Val Verde county. It has about the distribution of Holospira 
goldjussi and Helicodiscus eigenmannt. 
This very pretty little species has a slightly more ample umbilicus 
than V. wheatleyi or petrophila, and the sculpture is closer and more 
regular than in either. The last whorl, in dorsal view, is wider than 
in V. wheatleyi. It is much smaller than V. hammonis. 
V. dalliana roemeri attains a larger size than the Floridian V. dalliana 
and the shells have somewhat more regular and crowded grooves on 
