140 



PROCEEDINGS OF THE ACADEMY OF 



[Feb., 



Length 2 . 5, diam. 1 . 1 mm. ) „ , „ ~ c 00 



„ 22 " ii " i Cotyp^ Tanner Can y° n » fi s- 32 - 



2.15, " 1.1 " Santa Rita Mountains, fig. 33. 



Southeastern Arizona: Chiricahua Mountains, White Tail Canyon; 

 Summit of Cross J Mountain, Big Emigrant Canyon (Ferriss and 

 Pilsbry). Huachuca Mountains, Tanner Canyon, 6,000 feet (Ferriss, 

 type loc). Santa Rita Mountains (Ashmun). 



Fig. 32. — Bifidaria cochisensis P. and F. Types from Tanner Canyon, Huachuca 



Mountains. 



The absence of a forward continuation of the columellar lamella 

 on the parietal wall, between the parietal lamella and the columellar 

 wall, is the most prominent feature of this species, though it has several 

 other constant, if less conspicuous, differential characters. It is de- 

 cidedly less aberrant than B. ashmuni, the lamellae and folds, as well 

 as the less protracted last whorl, approaching the normal Bifidaria 

 type. 



A modification of B. cochisensis also occurs in the Huachucas at 

 Tanner Canyon and in the Chiricahua range on Limestone Mountain. 

 The shell is smaller than usual in cochisensis, about 1 . 9 or 2 mm. long. 

 The teeth are much weaker, especially the angular lamella. The 

 inner end of the parietal lamella is not much curved and is readily 

 visible in an obliquely basal view in the aperture. The basal and 

 palatal folds are less deeply placed, the lower palatal being visible 

 below the apex of the parietal barrier in a front view. The basal 



