1911.] NATURAL SCIENCES OF PHILADELPHIA. 191 



diam. about 19 mm. At Station 16, 80 per cent, of the shells are 

 bandless. 



(15) On the east side of the Powell Plateau, Stations 10, 103, 8, 12, 

 the shells are typical two-banded depressa (PI. XIV, figs. 17, 18, 19, 

 Station 103, 6,700 feet) varying to forms with the spire higher (figs. 

 20, 21, same station). Fig. 21, alt. 12.3, diam. 18, umbilicus -A nun. 



Thysanophora ingersolli (Bid.). 



Bill Williams Mountain ; Two-Spring Gulch, Kaibab Saddle. 



Thysanophora hornii (Gabb). 



Shinumo Creek, on the north side of the Grand Canyon. Farther 

 north than this species has been reported hitherto. 



ENDODONTID^. 



Pyramdula (Gonyodiscus) cronkhitei (Newc). 



Bill Williams Mountain. It was not found in the Grand Canyon, 

 but north of it was taken at Castle Springs and Rigg's Spring, Snake 

 Gulch, Kaibab Plateau; Mt. Trumbull; also Deception Lake and 

 Crocodile Lake near Kanab, Utah, 5,500 feet elevation. 



ZONITIDJE. 



Vitrina alaskana Dall. 



V. Pfeifferi Newc. not of Desh. 



Living specimens were taken on Bill Williams Mountain. Numerous 

 dead shells were found near a small spring in the Grand Canyon below 

 the cross-bed sandstone, 2 miles west of Mystic Spring Trail. This 

 spring is called Seep Spring on the topographic map, Shinumo 

 quadrangle. The average size of adults here seems to be about 6 mm. 

 diam., but one shell measures 7.4 mm. We did not find Vitrina 

 elsewhere in the Grand Canyon, but northward it occurred at Warm 

 Spring Canyon and Rigg's Spring, Kaibab Plateau, and at Mt. Trum- 

 bull. 



The living animal observed October 15, at Bill Williams Mountain, 

 is far less voluminous than V. limpida. There is one small shell-lobe, 

 covering the termination of the suture. In progression the tail does 

 not project behind the shell. 



Vitrea indentata umbilicatac 'Singl.' Ckll. 



Bill Williams Mountain. Grand Canyon along the Bright Angel 

 Trail from just below the rim to the base of cross-bed sandstone and 

 at the Indian Gardens; Bass Station, Grand Canyon R. R.; Station 

 H, on the north side of the canyon. Also taken on the north side of 



