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404 PROCEEDINGS OF THE ACADEMY OF (June, 
Black Mountain is a rather remote and isolated outlier of the 
Tucson Range, which has here its southeastern terminus. It is a 
long, straight, level-topped ridge, divided by a deep gap into a 
longer and a shorter mountain. The slopes are everywhere very 
steep, covered with black basalt, like Tumamoc Hill at Tucson. 
Slides of this rock occupy a large part of the slopes. Between the 
slides, which are, of course, barren of vegetation, there is some desert 
verdure. Ocotillo, mesquite, cat-claw, palo verde, etc., are typical 
plants, and giant cacti grow on the south side. No agave or sotol 
were seen. The Sonorellas are found rather deep in the slides. 
They probably inhabit the whole northern slope, but we worked 
only a couple of hours, on the north side of the east end, close under 
the summit. Some hazard attends the hunt in these slides, which 
are so steep that the heavy rock starts to move on small provocation. 
Black Mountain, like the rest of the Tucson Range, is very dry. 
It stands on a plain much lower than the Mineral Hill group and 
higher than Tucson. The station where Sonorella was collected 
we would roughly estimate as 3,200 or 3,300 feet above the sea. 
Sonorella eremita n. sp. Pl. VIII, figs. 7 to 7e. 
The shell is globose-depressed, umbilicate (the width of umbilicus 
contained about 63 times in the diameter of shell), more solid than — 
other species of the same region, glossy, pinkish buff, fading to nearly 
white around the umbilicus, and having a chestnut-brown shoulder 
band, without noticeable light borders. The embryonic shell, of 
about 14 whorls, has strongly developed sculpture of the hachitana — 
type. The initial half-whorl has some radial ripples or wrinkles; — 
then there appears a series of long, protractive threads on the outer ~ 
two-thirds, meeting shorter forwardly ascending threads on the 7 
inner third; the intervals occupied by short radial impressions. — 
The threads are subject to more or less interruption, particularly ? 
on the greatest convexity of the whorl. The later whorls are marked 
with very fine, unequal growth-lines. } 
The spire is very low, conoidal. Whorls 43, moderately convex, 
the last slowly descending in front. The oblique aperture is rounded, 
but slightly wider than high. Peristome slightly expanded above, — 
the outer and basal margins expanding more, slightly thickened, - 
the margins converging, connected by a very thin parietal film. 
Alt. 11.9, diam. 19.3 mm.; umbilicus 3 mm. 
West end of San Xavier Hill, Mineral Hill group, about 20 miles 
S. S. W. of Tucson, Pima Co., Arizona. Types No. 112,161, A. Ne 
S. P., collected by Pilsbry and Daniels, 1910. Topotypes in col- 
lections of Ferriss and Daniels. 
