1906.1 



NATURAL SCIENCES OF PHILADELPHIA. 



151 



Vitrea hammouis (Strom). 



Drift of the Pecos river at Pecos, New Mexico (Cockerell). The 

 specimens scarely show a trace of spiral hues. The species is unknown 

 in the Austroriparian and Lower Sonoran zones. 



Vitrea dalliana roemori n. subsp. Fig. 8. 



Shell openly umbilicate, the width of umbilicus contained about 

 4f times in the diameter of the shell, pale whitish-corneous, in general 

 shape resembling V. dalliana, V. wheatleyi 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 striae. 

 The base is nearly smooth. Whorls 4^, 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. — \'iirea tkdliana roemeri. 



Sinking Spring creek, near San Marcos, Hays county, Texas. Types 

 No. 91,318, A. N. S. Phila., collected by Pilsbry and Ferriss, 1903. 

 Also taken in several places around New Braunfels, Comal county; in 

 the drift debris 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 

 goldfussi and Helicodiscus eigenmanni. 



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 



