and of papillae on the next whorl. The much larger penis, its length nearly equal to the diameter of the shell, and the long, club-shaped verge, differentiate verdensis from other species of central Arizona. These characters, as well as the lack of diagonal threads mentioned, ally this snail to S. ambigua, which is widely spread in the mountains of the desert region a hundred miles south. Almost nothing is known of the shells of this hundred miles between the Mazatzal and the Silverbell ranges west of Superior and Ray, and the mountains around Phoenix arc equally unknown. Perhaps S. verdensis is a northern outlier of S. ambigua, or a derivative of galiurensis which has lost part of the embryonic sculpture; but until further collections are made, no definite opinion can be formed. S. ashmuni has a narrower umbilicus.
At Pine Creek Natural Bridge, about 15 miles north of the Mazatzal range, Ferriss collected a long series of similar shells, none alive. These shells vary from 13.5 x 23 mm. to 17 x 28.5 mm.; 4-3/4 whorls (Fig. 171 b, c).
(Named for the Verde River valley, in which the localities lie.)
Sonorella optata Pilsbry & Ferriss Fig. 173.
Sonorella optata Pilsbry & Ferriss, 1910, Proc. Acad. Nat. Sci. Phila., p. 60, pl. 1 figs. 6-12. 17-19; pl. 4, figs. 1-4. 7; text-fig. 4 (" S. optima " by error, l. c. p. 58).
Fig. 173. Sonorella optata. Upper, type and paratypes; middle left, cleft at fork of Emigrant Canyon; lower left, head Emigrant Canyon; other figures, west side of Rough Mountain.
The shell is umbilicate, umbilicus contained 6 times in the diameter; similar to S. hachitana. Pale brown, fading to whitish around the umbilicus,
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