46 GASTROCOPTA, NORTH AMERICA, WEST INDIES. 



Mts., in Tanner canyon (Ferriss). Santa Rita Mountains (E. 

 H. Ashmun). Drift of the Santa Cruz River, Pima Co. (Pils- 

 bry). Santa Catalina Mts. at Alder Springs and Marble 

 Peak (Ferriss). 



Bifidaria cochisensis PILSBRY and FERRISS, Proc. A. N. S. 

 Phila., 1910, p. 139, figs. 32, 33. 



This species differs from G. ashmuni in the following fea- 

 tures: All the teeth are smaller. The columellar lamella is 

 very much shorter, and does not continue forward upon the 

 parietal wall. The palatal plicae are less deeply immersed, all 

 being visible in a front view in the aperture. The parietal 

 and angular lamellae are much less curved. The last whorl 

 is less protracted, never free in front, with a lower crest or 

 wave on the neck, or none. 



It is far less widely distributed than G. ashmuni, and even 

 in its area is of less general occurrence, all of the known 

 localities being given above. 



11. GASTROCOPTA OLIGOBASODON (Pilsbry & Ferriss). PI. 7, 

 figs. 8, 9, 10, 11. 



The shell resembles G. cochisensis, from which it differs in 

 the following details : All of the teeth are smaller. The pari- 

 etal and angular lamellae are far less curved, and the angular 

 joins the parietal near the outer end of the latter. The colu- 

 mellar lamella is much shorter (pi. 7, fig. 8). The basal 

 plica is reduced to a minute tubercle, or in some individuals 

 it seems to be wanting. The parietal margin of the peristome 

 is adnate for a greater distance. 



Length 2.6, diam. 1.1 mm. 



Length 2.1, diam. 1 mm. 



Arizona: Ash canyon, Huachuca Mts., type loc. (Ferriss) ; 

 Lower Rucker canyon, Chiricahua Mts. (Ferriss). New Mex- 

 ico: drift debris of the Mimbres River at Swartz P. 0. and 

 near Deming (Pilsbry & Ferriss) ; debris of Rio Grande at 

 Mesilla (Cockerell). 



Bifidaria cochisensis oligobasodon PILS. & FERR., Proc. A. 

 N. S. Phila., 1910, p. 141, figs. 34a-c. 



This shell was formerly considered a subspecies of G. cochi- 



