1910.] NATURAL SCIENCES OF PHILADELPHIA. 117 
8,000 feet, Pine Canyon, 7,500 feet, and ‘‘ Box” of Rucker Canyon. It 
has been listed by Dall from Fly’s Park. 
While not strongly differentiated, adult shells of this race are readily 
distinguishable. The aperture clasps the preceding whorl less deeply 
than in ingersolli. The microscopic spiral striation also is somewhat 
better developed in the examples compared. 
Thysanophora ingersolli convexior (Ancey). Fig. 24, G, H, I. 
Microphysa ingersolli var. convexior Ancey, Conchol. Exch. II, p. 64, Nov., 
1887 (Logan Canyon, Utah). 
“Shell a little smaller; spire scarcely planulate, the apex not sub- 
immersed, distinctly convex; whorls 5, not 54, regularly but less 
slowly increasing, umbilicus smaller’? (Ancey). 
This form has not been figured. We have seen no topotypes, but 
examples from Weston, in eastern Oregon, collected by Henry Hemp- 
hill, evidently belong to the same race. One of these is figured (fig. 
24, 9, h, 7). Thespecimen figured measures, alt. 2.5, diam 4.8, width 
of umbilicus 1 mm., whorls 53. The aperture is a little wider than 
in typical ingersollt. 
Family UROCOPTIDA Pils. 
Genus HOLOSPIRA von Martens. 
All of the Holospiras now known from Arizona belong to a single 
group of closely related species, characterized by the light brown 
shell, having a stout lamella on the axis in the penultimate and first 
part of the last whorl, often in addition a superior or parietal lamella, 
and sometimes a basal lamella also. In several of the forms the 
lamelle vary from one to three, as we have demonstrated by cutting 
from twenty to fifty individuals of a single colony. In colonies so 
varying, the number of internal lamelle is not correllated with age, 
size or any other external feature of the shells, so far as we can discover, 
after collecting and examining hundreds of shells from a great number 
of colonies. The subgeneric divisions (Hudistemma, Tristemma) based 
upon the number of internal lamelle in shells of this type have, there- 
fore, no basis in nature. While the Arizona species differ somewhat 
from the Mexican type of the subgenus Bostrichocentrum in texture 
and sculpture, it does not seem that the differences are of subgeneric 
importance, and for the present we will place them in that group. 
The variations in the internal lamelle recorded below are really 
less discontinuous than might be supposed by the tables. The axial 
lamella is invariably present, but it varies in strength and length. 
The superior lamella may be very strong and over a half whorl long, 
