108 PROCEEDINGS OP THE ACADEMY OF [Feb. 



The specimens figured (topotypes) measure: Alt. 6, diam. 13 mm., 

 whorls 6f ; alt. 6, diam. 12.2 mm., whorls 6h. The smallest specimen 

 seen is from Rucker Canyon, 7,000 feet, measuring alt. 4.9, diam. 

 10.5 mm., whorls 5^. 



A. duplicidens stands veiy close to A. fissidens, but it differs by the 

 more obtuse, though bluntly angular, last whorl, and by the young- 

 shells, which form only a very thin, narrow rib within the lip in resting 

 stages, while in fissidens a very strong and heavy callus is deposited. 

 The basal teeth are more united than in typical fissidens. 



A. duplicidens, fissidens and proximo, are terms of one series of 

 forms differing chiefly, so far as the adult shells are concerned, in the 

 degree of separation of the basal tooth, which in duplicidens is a single 

 more or less bifid prominence, while in proximo there are two distinct 

 teeth. When the canyons opening westward, between Rucker and 

 Ft. Bowie, have supplied series of shells as copious as those we have 

 obtained in the eastward canyons, another chapter may be added to 

 the history of this group. 



Ashmunella angulata Pils. 



Proc. A. X. S. Phila., 190,5, p. 244. 



In the south fork of Cave Creek we found this species abundantly. 

 This is the type locality and here it attains the largest size. A few 

 dead ones were picked up on a mountain-side southeast of Paradise, 

 towards Cave Creek, and at Station 12, in Cave Creek. It reappears 

 at the head of the canyon at the Falls, and at Stations 3 and 4 and 

 in the head of Turkey Creek. At these places the shells are smaller. 



In 1907 Ferriss and Daniels took some specimens in Barfoot Park, 

 Station la. They are much less angular at the periphery than the 

 Cave Creek form. In 1908 it was taken in Horseshoe Canyon at the 

 "Red Box" (10 miles up the canyon) and at "5-mile camp"; also 

 in Rock Creek, at the head of Raspberry Gulch and in the Spring 

 Branch of Rucker Canyon. These localities greatly extend the range 

 of the species. The compressed outer basal tooth and less convex 

 whorls readily separate A. angulata from .4. proximo. Young shells 

 deposit a lip-callus at resting periods. It is thick in the middle, 

 tapering at the ends, as figured in our former paper, pi. XI, fig. 11. 



Our former figure of the genitalia of A. angulata (1905, pi. 21, fig. 26) 

 is not satisfactory in one point, the slight enlargement marking the 

 upper end of the penis being omitted. This enlargement is rather 

 small yet distinct in the individual figured, which has been re-examined, 

 and is present in all the specimens opened (seven) from several stations. 



