1910.] 



NATURAL SCIENCES OF PHILADELPHIA. 



139 



riss and Daniels); Nogales, S. Cruz Co. (Ashmun). New Mexico: 

 Valencia Co., along the Santa Fe R. R., at Grants (Ferriss and Pilsbry) 

 and San Rafael (Ashmun); Mountain Station, Oscura Mountains, 

 Socorro Co., and White Oaks, Lincoln Co., in Central New Mexico 

 (Ashmun) ; Cook's Peak (U. S. N. M.) ; Dripping Spring, Organ Moun- 

 tains (Cockerell); Florida Mountains, Luna Co. (Ferriss and Pilsbry). 



B. ashmuni is distinguished by the strong development of the 

 angulo-parietal lamella, which bends far to the right at its inner end, 

 the very deep immersion of the lower palatal and basal folds, the 

 continuation of the columellar lamella upon the parietal wall, alongside 

 the parietal lamella, and the longer, usually more gibbous, "neck" of 

 the last whorl. 



Fig. 31. — Bifidaria ashmuni minor Sterki, Nogales, Arizona. 



B. ashmuni minor Sterki (fig. 31) is a small race, length about 1.6 

 mm., with 4 to 4^ whorls, found at Nogales, Arizona, and also on the 

 Mexican side of the international boundary. The aperture is sub-- 

 stantiallv like that of ashmuni. 



Bifidaria cochisensis n. sp. Figs. 32, 33. 



The shell is slightly tapering cylindric, like B. ashmuni, but the 

 last whorl is less protracted and the crest or wave behind the aperture 

 is very low, often not noticeable. The peristome is continuous as a 

 slightly raised thread across the parietal wall (or in a less developed 

 form it is rather widely interrupted above). Lamellae weaker than in 

 typical B. ashmuni, especially the angular lamella, which is straighter; 

 parietal lamella less curved at its inner end. Columellar lamella wide 

 and horizontal, not continued upon the parietal wall. Basal and lower 

 palatal folds less deeply immersed than in B. ashmuni, readily visible 

 in the mouth, the basal fold small. 



