1910.] NATURAL SCIENCES OF PHILADELPHIA. 99 
thin, corneous-brown. The surface is lusterless, sculptured with fine, 
unequal wrinkle-striz, and covered with a network of cuticular scales 
or processes (readily removed by cleaning). There are 53 whorls, 
the first one corneous and glossy, the first three convex; subsequent 
whorls convex above, impressed above the lower suture; last whorl is 
distinctly impressed above the projecting peripheral keel, the base 
convex; in front it descends slightly or not at all to the aperture, and 
is narrowly, rather deeply, guttered close behind the lip on the base. 
The aperture is lunate, contracted by four teeth: a wide one within 
the outer lip, two contiguous tubercles in the basal lip, and an oblique 
straight parietal tooth. Parietal callus thin and transparent. 
Alt. 4.8, diam. 11.7 mm. 
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White Tail Canyon, on the northern side only, at Stations 10, 11, 16, 
17, etc., in “slides”? of igenous rock (rhyolite); type locality, Station 
11, in a slide of angular rhyolite, coming down to the trail in the bed 
of the canyon, with Sonorella micra. See map on p. 75. 
Genitalia are of the type usual in the fissidens group. The epi 
phallus and spermatheca are a little shorter, proportionately, than in 
A. p. albicauda or emigrans. Measurements of the organs of three 
individuals may be found in the table on p. 97. The mantle within 
the last whorl is cream-white with a few inconspicuous gray dots; 
collar pale slate-tinted. 
This species, of which several hundred specimens were taken, 
inhabits suitable rock-slides over the whole northern side of White 
Tail Canyon. At Station 11 it occurs close to the bottom of the 
canyon, and only a short distance from where A. fiss¢dens is found on 
the opposite side. The slopes of this side of the canyon are steep, 
interrupted by cliffs, and the heights are difficult of access. At 
Station 16 there are extensive rock slides sloping northward towards 
the mesa, and perhaps 1,500 feet higher than Station 11. Here it 
passes over the ridge and inhabits the opposite slope. While belonging 
to the fissidens group, this species is very distinct by its sculpture of 
cuticular scales, the strong carination, thin texture, etc. The young 
shells form only a weak callous rib within the lip at resting periods. 
At all the stations there is considerable variation in size and, as in 
all Chiricahua Ashmunellas, the height of the spire varies a good deal 
among individuals of any colony. At Station 17 the shells average 
