1911.] NATURAL SCIENCES OF PHILADELPHIA. 185 
are visible on the base in front of the aperture in most of the shells. 
The aperture is contracted less than in O. y. profundorum and the 
peristome is not thickened. The largest examples measure, alt. 8.2, 
diam. 16 mm., the smallest alt. 8.38, diam. 14 mm. About 60 adults 
examined. 
Fig. 18. Alt. 8.0, diam. 15.8 mm.; width of umbilicus 4.7 mm. 
(73 19. cc fess a3 14.5 ec as (73 4.0 a3 
73 19. (a3 8.7, a3 14.2 ce ec ce 4.0 a3 
Uae toro, cl EGO °° Ss ie 43 “ 
eee On. 5.5: HS i 4.3 
Cotypes are No. 103,236 A. N.S. P., collected by Ferriss and Pils- 
bry, 1906. 
Similar shells occur on the upper slope at the same level, in a bay 
of the rim, about a half-mile west of Bass’s Camp, on the southern 
rim of the canyon (pl. XII, figs. 15, 16, 17). 
Fig. 15. Alt. 9.2, diam. 15.5 mm.; umbilicus 4.0 mm. wide. 
ie TUS) Caer i a i UF Oi . 4. Te ‘ 
eee l aaa. Rennie sh) pO Ope Me ss 45Or st e 
Oreohelix yavapai angelica. PI. XII, figs. 22-25. 
On the Bright Angel Trail, at Grand Canyon, from 100 to 400 feet 
below the rim, which has here an elevation of 6,866 feet, the shells 
resemble O. y. extremitatis in contour, except that the last whorl is 
somewhat more inflated. The color is light brown, usually with a 
brown band below the periphery, sometimes with another above, but 
this is often wanting. It is thinner and larger than extremitatis, and 
spaced spirals are more distinct, being well-developed on both the 
base and upper surface. The embryonic whorls have faint spiral 
lines. The first part of the neanic stage (up to at least 11 mm. diam., 
with nearly 4 whorls in some individuals) bears spiral rows of cuticular 
scales readily visible to the naked eye. There are about 8 spirals 
above, 10 below the periphery on the last whorl. The last whorl is 
but slightly deflexed in most examples, rarely (8 per cent.) more or 
less deeply so, approaching fig. 25, which is an extreme individual. 
Fig. 22. Alt. 9.0, diam. 17.0 mm.; width of umbilicus 4.5 mm. 
ce 23. a3 9:2: cc 170) zs ee “ce 49 ce 
cc 24. a9 9.2, ce 17.9 ce oe ce 48 “ce 
po ee NODE eg NBO" ~ ico eg 
Individuals with deeply descending last whorl occurred chiefly at 
the lower level. 
