334 PROCEEDINGS OF THE ACADEMY OF [May, 



Oreohelix ferrissi morticina n. subsp Plate VI, fig. 3. 



Differs from 0. ferrissi by the more convex spire and by the weak- 

 ness of the spiral sculpture, there being no such pronounced spiral 

 ridge on the upper surface of the whorls, and only very weakly 

 sketched spirals on the base, whilst in 0. ferrissi these ridges are very 

 emphatic. 



Alt: 7.2, diam. 14.2 mm.; 4f whorls. 



Station 5, below the cliffs on the north side of Daniels Mountain, 

 near the summit, with Holospira, etc. 



Only a few long-dead shells were taken, I^ut these surely indicate 

 a local race which has finally succumbed to the increasing aridity 

 of their station. Of large shells only Holospira and Ashmunella 

 survive on this mountain, both of them being burrowing animals. 



Thysanophora hornii (Gabb). 



Found at Stations 3 and 5. It is an almost ubiquitous Lower 

 Sonoran snail. 



UROCOPTIDuE. 



The study of a very large series of Hachita Holospiras has fully 

 confirmed the results reached in our study of Chiricahuan species, 

 that the number of internal lamellse is variable in each species and 

 colony, among perfectly mature or even aged individuals. They 

 vary in a way it was impossible to foresee at the time when Holo- 

 spiras were so rare that only one or two of a lot could be opened. 

 Very naturally, the number of internal lamellse was thought at that 

 time to be of specific and even subgeneric value. 



In some colonies it appears that the largest shells have in the 

 average the greatest development of lamellse, so that it might be 

 thought that only the most vigorous individuals attain the full 

 number; yet other races or colonies give a contrary result. No 

 external character is correllated with the number of lamellse. Usually 

 most of the shells of any one colony resemble each other in size, 

 shape and sculpture, so that each lot has a certain individuality, 

 though all of the characters vary more than is usual among the 

 land snails. We have never found two species of Holospira living 

 in one colony, either in the Hachitas or in any other district, in the 

 course of several years, collecting, in many places in Texas, New 

 Mexico and Arizona. 



A comparison of the Holospiras of the Hachita Grande range with 

 those of the Chiricahua range shows some interesting resemblances 

 and differences. In both localities the internal lamellse present (in 



