GASTROCOPTA, NORTH AMERICA, WEST INDIES. 37 



Ana Co. (Cockerell) ; Florida Mts., Luna Co. (Pilsbry & 

 Ferriss) ; Big Hatchet Mts., Grant Co. (Pilsbry). 



Arizona: Mt. Trumbull and Kaibab Plateau (Ferriss & 

 Daniels), Grand Canyon, Bill Williams Mt. (Pilsbry & Fer- 

 riss), Flagstaff (Ashmun), Coconino Co.; Jerome, Yavapai 

 Co. ; Holbrook, Navajo Co. ; Navajo Springs, Apache Co. 

 (Ashmun) ; Blue River and Eagle Creek, Graham Co.; Santa 

 Catalina Mts., Pima Co. (Ferriss) ; Chiricahua and Dragoon 

 Mts. (Pilsbry & Ferriss), and Huachuca Mts. (Ferriss), Co- 

 chise Co.; Santa Rita Mts., 20 miles from Crittenden, Santa 

 Cruz Co. (Ashmun). Type locality, Colorado River, Arizona. 



Pupa pilsbryana STERKI, Nautilus, iii, March, 1890, p. 123. 

 Bifidaria pilsbryana Sterki, Pilsbry, Nautilus, xi, p. 118. 

 PILSBRY and COCKERELL, Nautilus, xiv, pp. 85, 86. VANATTA, 

 Nautilus, xvi, p. 58. ASHMUN, Nautilus, xiii, p. 14. PILS- 

 BRY and FERRISS, Proc. A. N. S. Phila., 1909, p. 415; 1910, 

 p. 136. WALKER, Occ. Pap. Mus. Zool. Univ. Mich., No. 15, 

 1915, pp. 2, 3 (Canones Creek, east of Mt. Pedernal, and 

 vicinity of Puerco Creek, Rio Arribo Co., N. M., Case). 



G. pilsbryana is similar to slender examples of G. pentodon 

 in shape and color, but it differs by having the lip thin, with- 

 out any internal callous whatever, and there are never more 

 than five teeth, but always five in adult shells. It has some 

 resemblance to G. pellucida, but is retained in the section 

 Vertigopsis because the parietal lamella is simple, an angular 

 lamella being entirely wanting; but more because the basal 

 fold is placed rather far to the left, a special character of 

 Vertigopsis. The columellar lamella is a directly horizontal 

 and rather short tubercle, not descending as in pentodon. 



There is considerable variation in the size of the teeth, and 

 also in the size of the shell, even in the same lots. The length 

 varies from 1.65 to 1.9 mm. 



This is one of the commonest species in the mountains or 

 plateaus of over 4000 ft. elevation in both New Mexico and 

 Arizona. Excepting the practically unexplored northern tier 

 of counties in New Mexico, and the equally unknown two 

 western counties of Arizona, it is known to occur in suitable 

 places all over both states ; but in the south these places are 



