———eeo ee eee el .hlrtC<CMS 
= 
1911.] NATURAL SCIENCES OF PHILADELPHIA. 189 
At Station 60 only fossil examples were taken. 
Fig. 8. Alt. 9.8, diam. 21.0, umbilicus 6.5 mm. (Station 62). 
ee ain by 2a | Bae CT” 61). 
(7) At Snake Gulch, below the Coconino Smelter, Station 49, the 
shells resemble those from Station 66, having a low conoidal spire 
and depressed last whorl which falls decidedly at the aperture. Bands. 
narrow, rather pale. 
(8) At Station 37, Snake 
Smelter Gulch, elevation 5,750 feet, t 
Station 50 (see fig. 11). 
(9) At Castle Springs, Station 79, the shells are large and dark, 
two-banded or more or less clouded (PI. figs. 19-21, 6,750 feet elevation). 
Similar examples are found at Riggs Spring, Station 81. 
Fig. 19. Alt. 11.8, diam. 29.0 mm. (Station 79). 
Gulch, at the north side of the mouth of 
he shells resemble those from 
oes 15.5, 23. “ wmbilicus 6.2 mm. (Station 79). 
“cc Bhs ims LOE oe 92.2) oe ce 5.3 oc ( oe oe ) 
Between the preceding and following stations there is an interval 
of about 13 miles over the watershed in which no Oreohelices were 
found. 
anyon penetrates the Kaibab Plateau from 
(10) Quaking Asp C 
the west, where it drains into Tapeats Creek. Two-Springs Canyon 
is a branch of the head of Quaking Asp. From the lower end of 
Quaking Asp Canyon, Station 98, 6,500 feet elevation, to the head, 
Station 83, 8,250 feet, there is a gradual diminution in size of the shells, 
¢ aridity of the higher stations westward. 
no doubt due to increasing 
At Station 98 the shells are very large, diam. 22 to 26 mm., but 
typical in form and color (Pl. XIII, figs. 24-26). At Station 97 the 
size averages smaller, and there are some albino shells, white with 
translucent, greenish bands, At Stations 99, 96, 94, 93, 92, 91, 90, 
89, 87, 88 there are similar shells, the size diminished a little (Pl. XIU, 
figs. 22, 23, Station 91, 7,000 feet). 
Stations 86, 85, 84 and 83 show shells still further diminished, adults 
measuring, alt. 9 diam. 14 to alt. 7, diam. 11.5 mm., with 43 whorls 
(Pl. XIU, figs. 27, 28, Station 84). The color is typical; the periphery 
angular in front and the last whorl descends only very little to the 
These colonies show no senile features. Their develop- 
aperture. 
and the angular 
ment has been arrested, the small number of whorls 
periphery being characters of youth. 
At Two Springs, Station 27, the shells resemble those from Station 
91. Farther up the canyon, Station 26, the shells became smaller, 
