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 



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 Fe, 

 at El Tovar, the Bright Angel Trail. 1 

 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 eolor- 

 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 

 Pupillidse 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. 



xBass camp 



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. 



