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 lamellae to- 

 gether forming a figure like the letter <*. The columellar lamella is 

 broad and horizontal far within, but near the aperture it 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 lamellae 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, Mescal 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- 



