138 PROCEEDINGS OF THE ACADEMY OF [Feb., 
peristome is well expanded, continuous, and usually stands shortly 
free from the whorl in front. The parietal lamella is sigmoid, bending 
far to the right at its inner end. The angular lamella, also sigmoid, 
runs from the peristome to the parietal lamella, the two lamelle to- 
gether forming a figure like the letter 4. The columellar lamella is 
broad and horizontal far within, but near the aperture 7 runs out 
upon the parietal wall, where it appears as a more or less elevated 
cord between the parietal lamella and the columella, occupying, 
therefore, the place of an infraparietal lamella. These lamelle are 
well shown in fig. 30 b, a basal view in which the base of the shell has 
been removed. The upper palatal fold is short, situated some distance 
within the mouth, but visible from in front. The lower palatal is long, 
entering, and so deeply immersed that it is not visible in a front view, 
being concealed behind the massive parietal barrier. There is a radially 
placed basal fold, scarcely or not visible in a front view. Length 
about 2, diam. 1 mm. 
Fig. 30.—Bifidaria ashmuni Sterki. A, B, Florida Mountains, New Mexico; 
C, Page’s Ranch, Oak Creek, Central Arizona. 
Arizona: Coconino Co., Grand Canyon, on the Bright Angel trail 
about 100 feet below the rim (Ferriss and Pilsbry); Yavapai Co., 
Verde River, Walnut Gulch, Meseal Gulch and Kirwagen’s ranch, all 
near Jerome, and along Oak Creek at Owensby’s and Page’s ranch; 
along the Santa Fe R. R. at Holbrook, Navajo Co., and Navajo Springs, 
Apache Co. (Ashmun); Cochise Co., in the Chiricahua range in White 
Tail Canyon below the mouth of Indian Creek and on Limestone 
Mountain (Ferriss and Pilsbry); Ash Canon, Huachuca range (Fer- 
-o-— = 
