106 PROCEEDINGS OF THE ACADEMY OF [Feb., 
in 1908. The shells are similar to those of White Tail Canyon in general 
appearance, but differ in certain particulars, constituting a minor 
race. They are in the average smaller, diam. 84 to 114 mm., rarely 
13 mm., with 54 whorls; the umbilicus is noticeably wider; the lip is 
heavy and wide. The basal teeth vary from completely united to 
distinctly bifid, as in White Tail fissidens, or rarely they are almost 
separated. In most examples these teeth are more united than in 
White Tail specimens. The shape of the parietal tooth also varies 
from V-shaped to simple. All of the shells"are more angular and more 
depressed than A. duplicidens. 
Ashmunella duplicidens Pils. Pl. VIII, figs. 1-8. 
Proc. A. N.S. Phila. 1905, p. 244. 
After. the first 14 whorls the next four whorls more or less appear 
minutely punctate in the best preserved examples, though in most 
only an indistinctly interrupted condition of the striz can be made 
out. Under the compound microscope some very fine close spiral 
striation is seen on the base. The basal tooth is ordinarily doubled 
as in figs 5 and 8; but sometimes is simple, the inner tubercle being 
represented only by a sloping callus, as in figs. 1-3, 6, 17. 
Immature shells form only a thin narrow rib within the lip at resting 
stages, and have a wider, somewhat less angular, aperture than A. 
fissidens. This thin lip-rib is subsequently wholly, or almost wholly, 
absorbed, so that adult shells do not show whitish varix-streaks. 
Figs. 3 and 7 show the extremes of elevation and depression of the 
spire. All of these figures are from topotypes, from Station 1 in 
Barfoot Park—an extensive slide of coarse rock on a southern exposure. 
It is an abundant species in this place. 
In 1907 Mr. Ferriss found A. duplicidens in the head of Morse Canyon, 
large shells, 13 to 14mm. diam., with over 6 whorls; in Rucker Canyon, 
7,000 to 8,000 feet; and on Rucker Peak, where they are also rather 
large. Small shells, 10.5 to 11.5 mm. diam., were taken at the Box of 
Rucker. A specimen from Crook’s Peak measures 14 mm. diam. 
Large and well-developed duplicidens was found in Cave Creek 
Canyon on the first branch west of the Falls fork of Cave Creek, diam. 
14 to 15 mm., and at the Falls. é 
The genitalia of a specimen from the head of Morse Canyon are 
figured, pl. X, fig. 8. The penis tapers more gradually than in allied 
forms, the distinction between its swollen basal half and the slender 
distal portion being obscure. This was also the case in the individual 
figured in 1905 from the type lot, but in that preparation the enlarged 
basal portion of the penis was everted, hence does not show at all in 
