98 PROCEEDINGS OF THE ACADEMY OF [Feb., 
Group of Ashmunella proxima. 
From Old Fort Bowie these forms extend southeastward to the end 
of the Chiricahua range. Northward beyond the depression at the 
Fort, in the Dos Cabezas end of the range, no Ashmunella has been 
found. The mountains here are apparently too barren and dry for 
Ashmunella, though they support the more hardy Sonorellas. 
The colonies seem to be small and widely separated in the area 
northwestward of White Tail Canyon, but much of that country remains 
to be explored, especially between Big Emigrant and White Tail 
Canyons, as well as the entire region of the southwestern watershed. 
A. ferrissi and A. angulata are distinct from the others by their 
flattened whorls and conspicuously compressed outer basal tooth. 
The other species are intimately related, and their variations make 
a complexly branching form-chain. An adequate study of the 
material in hand, some thousands of shells, would require more ample 
time than we can give. Since not half of the territory is adequately 
covered by our series, we must leave full consideration of the subject 
for another occasion. 
Our knowledge of the forms from Rucker and Horseshoe Canyons 
and the region around them is still very defective. The forms seem 
to be related somewhat, as shown in the following diagram: 
proxima 
emigrans lepiderma 
pomeroyt, albicauda—fissidens 
duplicidens 
If a single basal tooth is primitive, then A. duplicidens is the least 
evolved member of the series and of the whole Chiricahuan group of 
Ashmunellas. Then A. proxima and lepiderma would be the most 
evolved. All of the forms with more or less concrescent basal teeth 
are extremely variable in the degree of union of these teeth. Every 
colony of fissidens, emigrans, albicauda, pomeroy: and duplicidens 
shows great individual variation in this respect. There seems to be 
complete intergradation between the separated basal teeth of proxima 
and the united teeth or single tooth of fissidens and duplicidens. 
Ashmunella lepiderma n. sp. PI. VII, figs. 1-7. 
Shell umbilicate, the umbilicus about one-fifth the total diameter 
of the shell, much depressed, biconvex, acutely carinated peripherally, 
