374 



PROCEEDINGS OF THE ACADEMY OF 



[June, 



Length 11.5, diam. 3.5 mm.; 12| whorls. 



Dragoon Mountains, Cochise County, Arizona, from Tweed Can- 

 yon to the northern end of the range, on hmestone, under stones, 

 dead agaves, sotols, etc. Type locaUty Station No. 2, Tweed 

 Canyon, No. 112,199. A. N. S. P. 



They live on the most exposed, hottest slopes, often in great 

 profusion, but are not found on the mesa, where H. campestris 

 occurs. 



This beautiful snail is very distinct from all of our species by its 

 strong, rude, widely spaced ribs. One of the northwest Mexican 

 Holospiras, H. minima, has the same type of sculpture, though less 

 coarse than in the typical H. danielsi, which is the most strongly 

 costate species known. 



Like other Arizonian Holospiras, the internal lamellae are variable, 

 two or three (parietal and axial, or parietal, axial and basal) being 

 developed. Otherwise the chief variation is in the number of ribs, 

 and also in size. 



Twenty specimens of the type lot, opened, taken at random, 

 measure as follows: 



Length 12, diam. 3.6 mm.; whorls 13; lamellae 2. 



The smallest shell noticed in the type lot measures 8.2 x 3.2 mm., 

 with 10 whorls. The trilamellate shells are shghtly outnumbered 

 by those with two lamellae, forming 45 per cent, in the lot measured; 

 but this may be accidental. Three lamellae predominate in the 

 larger shells, two in the smaller. 



