73 



ON THE GENUS ASHMUNELLA, PILS. &. CKLL 



By C. F. AXCEV. 



WITH ANATOMICAL NOTES, 



Bv R. MURDOCH. 



(riate vii.) 



The genus AsltmnnelJa was established by Messrs. H. A. Pilsbry and 

 and T. D. A. Cockerell/ for the reception of some sliells, externally 

 difficult to separate from Pohjijijra, and especially from the group 

 generally known as Triodopsis. The form and texture of the shell, 

 form of the aperture, and teeth when present, do not furnish a single 

 character that would separate them from Pohjgijra. Strangely enough 

 the soft parts differ anatomically, and the geographical distribution is 

 peculiar. All the species are confined to the boundaries of New 

 Mexico and Arizona. These, say Pilsbry and Cockerell, "fairly define 

 a region of arid plains from which rise numerous mountain ranges, 

 upon whose summits the humidity refused by the dry and warmer air 

 of the plains is precipitated. Upon the elevations thus set apart by 

 the circumstance of a moister and colder climate, the snails inhabiting 

 the region are chiefly found. And standing island-like in a waterless 

 sea, the mountains exhibit to a considerable extent the peculiarities of 

 insular faunas, each range having its own special assembly of forms, 

 specific or varietal, in addition to a series of species common to 

 ranges over the greater part of the region." These mountains are the 

 home of Asliimmella, a genus which occurs in New Mexico from 

 the latitude of Santa Fe to the White Mountains (Sierra Blanca), and 

 westward to S.E. Arizona. 



The authors above cited state that the shell offers no characters 

 different from Triodopsis or Mesudon sections of Fohjgijra, and that 

 " it is helicoid, depressed and umbilicated, dull coloured, not banded 

 so far as known, with lunate aperture and reflexed peristome: parietal 

 tooth, when present, simple, not v-shaped or biramose." 



My observations are quite in accord with the above, but, in my 

 opinion Folngyra mearnsii, Dall, and P. levcitei, Bland, probably are 

 members of the genus and hitherto the most toothed forms known. 

 They belong to the same region, and their soft parts being unknown, 

 I am inclined to place both species in this group, rather than in the 



I Proc. Acad. Nat. Sci. Phila., 1899, p. 188. 



