188 PROCEEDINGS OF THE ACADEMY OF 



ASHMUNELLA, A NEW GENUS OF HELICES. 

 BY H. A. PILSBRY AND T. D. A. COCKERELL.^ 



The boundaries of New Mexico and Arizona 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 consider- 

 able 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. 



A characteristic element in this fauna is ihe series of helicoid 

 enails now segregated under the generic name Ashmunella, so called 

 in recognition of the fact that the Rev. E. H. Ashmun, of 

 Albuquerque, N. M., discovered most of the species. This genus 

 occurs in New Mexico from the latitude of Santa Fe to the White 

 mountains, and westward to S. E. Arizona. It is not impossible 

 that it may yet be found in the Sierra Madre mountains of Mex- 

 ico ; but it surely does not extend to California or Colorado. It is 

 an interesting coincidence, if nothing more, that its northern limit 

 is nearly that of the supposed southern limit of glaciers in the 

 Rocky mountain region during the ice age. 



The more important characters of Ashmunella may be stated as 

 f olloAvs : 



Generic Characters of Ashmunella.^ 



The shell oflfers no characters different from the Triodopsis or 



^ We would here acknowledge our indebtedness to Mr. E. G. Vanatta for 

 the illustrations of this paper, the dissections from which they were drawn, 

 and various observations on the subject. 



One of the authors communicated the substance of this paper to the 

 Academy of Natural Sciences at the meeting of January 10, 1899, brief 

 notices of that communication appearing in Science, ix (new series), p. 182, 

 and Nautilus, xii, p. 107. 



* The internal anatomy is known in A. miorhyssa only, from specimens 

 collected by Prof. C. H. T. Townsend. 



