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. OORVe fog 07, US. L9; 
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 4 mm. 
‘Thysanophora ingersolli (Bld.). 
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 (Newe.). 
Bill Williams Mountain. It was not found in the Grand Canyon, 
put 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. 
ZONITIDA. 
Vitrina alaskana Dall. 
V. Pfeifferi Newe. 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 Vztrina 
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 umbilicatae ‘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 
