1923] NATURAL SCIENCES OF PHILADELPHIA 51 
heavy shade and a deep forest cover; in similar situations Polygyra 
albolabris, palliata and thyroidus are found in the east. 
April 8th, our expedition to Ajo was again under roof at Tucson, 
Many may make that journey in quicker time, but few will see as 
much between the two cities. In interest every day was filled to 
its full capacity.! 
Collections were made at the following stations in 1917-1918: 
(1-11. Baboquivart Range. See map, Text—fig. 8, on page 83.) 
1. Sycamore canyon, east bank of north fork, 100 yards above 
the fork, in stratified porphyry. 
2. 100 yards above station 1, west bank of north fork, in a slide. 
3. Half mile above station 2 on same fork; large slide opposite 
caverns. 
5. South slope of small hill north of camp, in a small pile of 
porphyry. 
6. High peak west of north from camp, slope overlooking 
Otero canyon. 
7. Tumble of porphyry cliffs, head of ridge. 
8. Near Station 7. 
9. Head of Otero canyon. 
10. High mountain 4 miles west of Station 9. 
11. Opposite Station 3. 
(Stations 12 to 45 and 48, in the Santa Catalina, Rincon, Galiuro 
and Tortillita Ranges, have been enumerated in these PROCEEDINGS 
for 1918, pp. 307, 308.) 
46. Silver Bell Range: slides on a quartzite hill northeast of the 
mine headquarters. 
47. Sierrita Range: largest canyon on the northeast, in bank of 
gulch and porphyry slides above. 
(53-90. Tucson Range) 
53. Half a mile northwest of Pictured Rocks. 
54. About 4 miles north of Station 53, one of several slides facing 
west, on the west side of the Range. 
55. Slide facing west, on the next mountain north. 
56. Slide facing south, same mountain. 
57. Table mountain, half a mile east of Station 54. 
58. About 3 miles south of Pictured Rocks, opposite Yuma mine 
(‘Mountain Sheep Camp”’). 
59. About 5 miles north of Mt. Sheep Camp, in a quartzite outlier 
west of the range, and a twin outlier of lime butte. 
1 Besides the well-known works of Lumholz and MacDougal, upon the Papago 
country, there has recently been issued a valuable paper by Kirk Bryan, “ Krosion 
and sedimentation in the Papago country, Arizona, with a sketch of thegeology.”’ 
U. S. Geol. Survey, Bulletin 730-B. 1922. 
