174 PROCEEDINGS OF THE ACADEMY OF [March, 
MOLLUSCA OF THE SOUTHWESTERN STATES, V: THE GRAND CANYON AND 
NORTHERN ARIZONA. 
BY HENRY A. PILSBRY AND JAMES H. FERRISS. 
Prior to 1906 the work on southwestern mollusks of the mountain 
region had been confined to southern and central New Mexico and 
-3 
IBASS CAMP 
a} 
Fig. 1—Grand Canyon in the 
vicinity of Bass Trail and 
Shinumo Creek, showing col- 
lecting stations, expedition 
of 1906. Reduced and sim- 
plified from U.S. Geol. Surv. 
Topographic map, Shinumo 
quadrangle, edit. of August, 
1908. 
Arizona. Between this region and the 
districts in Colorado and northern Utah 
which have been explored for snails, 
a great area, including the Grand 
Canyon of the Colorado, remained 
unworked. To obtain some knowl- 
edge of this region, the authors spent 
the month of October, 1906, in the 
Grand Canyon; also collecting on Bill 
Williams Mountain (elevation, 9,000 
feet), on the plateau of northern 
Arizona, 64 miles south of the Grand 
Canyon. In the canyon we collected 
at the terminus of the Grand Canyon 
Railroad, a branch of the Santa Fé, 
at El Tovar, the Bright Angel Trail,? 
and at many localities reached from 
Bass Trail (also known as the Mystic 
Spring Trail), 24 miles west of the 
railroad, and on both sides of the river. 
Most of our stations here are shown 
on the accompanying map (fig. 1). 
We did not visit John Hance’s trail, 
the Red Canyon Trail so-called, which 
lies east of Grand Canyon, the railroad 
terminus. One species, Sonorella color- 
adoensis, was taken here by Dr. C. Hart 
Merriam in 1889, but otherwise the 
snail fauna is unknown. The Grand 
View Trail is also unvisited by col- 
lectors of shells. The Oreohelices and 
Pupillide of the upper and intermediate 
slopes will doubtless prove interesting 
1 We are indebted to Dr. C. Montague Cooke, of Honolulu, for several species 
taken by him at the ‘‘Indian Gardens,” Bright Angel Trail. 
