334 PROCEEDINGS OF THE ACADEMY OF [May, 
Oreohelix ferrissi morticina n. subsp. Plate VI, fig. 3. 
Differs from O. 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 O. ferrissi these ridges are very ~ 
emphatie. 
Alt. 7.2, diam. 14.2 mm.; 4? whorls. 
Station 5, below the cliffs on the north side of Daniels Mountain, 
near the summit, with Holospira, ete. 
Only a few long-dead shells were taken, but 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. 
UROCOPTIDA. 
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 lamellze 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 lamelle 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 lamella, 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 lamelle. 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 lamelle present (in 
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