1911.] NATURAL SCIENCES OF PHILADELPHIA. 181 
the largest, alt. 12, diam. 17.2, umbilicus 2.5 mm. (F. and D. 1909). 
Some of these shells are the largest taken up to this time, exceeding 
the types. The shoulder-band is faint or wanting on some shells. 
(10) Station G: White Creek, about 1 mile above its confluence 
with Shinumo Creek (Pl. XII, figs. 26-28). Seven per cent. of the 
shells taken show a chestnut band. In the rest there is an ill-defined 
whitish band in its place. Bandless shells are rare in all other localities. 
The aperture is also more ample in this lot, somewhat trumpet-shaped, 
the lip is rather more thickened and rusty, and the parietal callus is 
generally thick at the edge. 
Alt. 10, diam. 17.0, umbilicus 2.6 mm.; aperture 8.8 x 10.0 mm. 
lO oe 16.2, a 7 SS SX 3 9lone | 
eee ee LD a Bacon" uf ote Vcwou ne 
The genitalia of a specimen of this lot are figured, fig. 3B. 
(11) Muav Box, Station 9, elevation 4,000 feet (F. and D., 1909). 
Diam. 15-16 mm. All taken have the shoulder-band. 
(12) Station H: Mojave Amphitheatre below the red-wall sand- 
stone (west side of Muav Canyon, near Dutton’s Point). The shells 
are all banded, measure 14 to 16 mm. diameter, and do not seem to 
differ from those taken on the Shinumo at a much lower elevation. 
At this point the authors made a dry camp in 1906, being unaware that 
there was water a few miles beyond. In 1909 Ferriss and Daniels 
took a fine lot of unusually large and dark colored Sonorellas at Station 
107, about two miles farther up Muav Canyon, but they were lost 
before reaching home. 
(13) Station 104, 6,700 feet, and Station 9, 7,500 feet, east side of 
Powell Plateau (west of Muav Wash). Small, 13.5 to 14 mm. diam.; 
banded; aperture dilated, as in the shells described under (10). This 
colony and those following were taken by Ferriss and Daniels, 1909. 
(14) Station 5, east of Muav Canyon, near the. Kaibab Saddle, 
6,717 feet. Small shells, diam. about 13.5 to 15 mm., with the mouth 
less dilated than in the preceding lot, nearly normal. All are banded. 
(15) Station 25, west side of Powell Plateau, 6,700 feet. The 
shells are small, diam. about 14 mm., with thickened lip and somewhat 
dilated mouth, ‘as in Nos. (13) and (19). 
(16) At Station 23, Horse Tank Canyon, on the west side of Powell 
Plateau, 7,000 feet, the shells are like those from No. (12). Some 
bandless individuals were also taken. 
(17) Station 101, north end of Powell Plateau, 6,700 feet. Only 
dead and bleached shells, normal in shape. 
(18) Station 100, third amphitheatre north of the Kaibab Saddle, 
