52 PROCEEDINGS OF THE ACADEMY OF [Feb., 



Thysanophora hornii, 14 H. F. Bifidaria pellucida hordeacella. 



Agrinlimax kemphilli ashmuni, 1 '* H. " quadridentata 15 H. 



Zonitoides milium meridionalis, H. " pilsbryana, H. F. 



minuscula alachuana, H. " perversa. 1 * 



Vitrea indentata umbilicata, H. " ashmuni 1 * H. F. 



Helicodiscus eigenmanni arizonensiSjJI. " cochisensis 1 * H. 

 Radiodiscus millccostatus 15 H. " dalliana. 1 * 



Punctum californicum. lh " tuba. 1 * 



Vallonia perspectiva 1 * H. F. Pisidium abditum huachucanum 15 , H. 



With the single exception of Agriolimax, all of these are very small 

 or minute snails, certainly capable of being carried long distances 

 by cyclonic winds, and it is likely that their wide distribution may be 

 attributed in part to such means, though it is not improbable that 

 a considerable number of the forms may have existed before the 

 isolation of the Arizona ranges. 



Twenty-two of the thirty species of groups 2 (a, b, c) have been 

 found in the Huachuca range. 16 These are indicated in the list above 

 by the letter H. Four species, marked F in the list, occur in the far 

 poorer fauna of the Florida Mountains. 



Faunal zones represented in the Chiricahuas are the Canadian, the 

 Transition, and the Upper Sonoran. Zones dependent upon elevation 

 are less distinctly marked in mollusks than in plants or vertebrates, 

 local exposure and suitable conditions of moisture controlling the 

 distribution of species to such an extent that the elevation zones are 

 extremely irregular. It appears, however, that the Canadian zone 

 forms are strictly confined to the high "parks" and peaks. The 

 characteristic Transition zone 'species are also for the most part high 

 on the range, as are also five species which, from their distribution 

 elsewhere, are considered to be Upper Sonoran. Seven of the eighteen 

 Upper Sonoran species have been found only below 7,000 feet, while 

 six have a general range. 



In the group of species peculiar to the Chiricahua range, and which 

 must apparently be considered Upper Sonoran, many of the forms 

 are very local in distribution and belong to the middle and lower zones 

 ■of the range. Those having a wider distribution often have a great 

 vertical range, as the following examples: 



14 Found only low, below 7,000 feet. 



15 As yet found only at about 8,000 feet or above, but none of them known 

 from much further north than the Chiricahua range. 



16 Proc. A. N. S. Phila. for 1909, pp. 498-516. 



