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. 8^ to 11^ mm., rarely 



13 mm., with 5£ 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. PI. VIII, figs. 1-8. 

 Proc. A. N. S. Phila. 1905, p. 244. 



After the first H 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 striae 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 14 mm. 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. 



The genitalia of a specimen from the head of Morse Canyon are 

 figured, pi. 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 



