1923] NATURAL SCIENCES OF PHILADELPHIA 101 
believe that the habitat of that species can now be fixed. Mearns 
was in camp at Tinajas Altas, at the east base of the Gila Moun- 
tains, from February 14 to 23, 1894, and made a careful exploration.? 
These famous natural rock tanks, which furnish an almost unfailing 
supply of good water, were an important camping place on the old 
Yuma Trail to California,’ and probably are where Frick obtained 
the type of Helix rowelli. In the absence of other information, 
we propose that Tinajas Altas be considered the type locality. 
M. rowelli stands close to M. hutsoni, but the aperture is more 
rounded, less oval, and the parietal callus is decidedly longer. 
The Mearns example measures: height 8, diam. 16.3 mm., and 
is figured on Plate III, fig.6. The parietal callus is not so heavy as 
in Newcomb’s type, which is evidently an old shell. 
Micrarionta newcombi n. sp. Plate III, fig. 8. 
The shell is strongly depressed, openly umbilicate (the umbilicus 
contained 4 times in the diameter), thin, whitish (dead), with a 
narrow brown band above the periphery. Surface smoothish, 
with faint growth striz only. Embryonic whorls showing no sculp- 
ture (somewhat worn). Whorls convex, rather slowly increasing. 
Aperture rounded-lunate. Peristome sharp, the specimen not 
fully mature. 
Height 8, diam. 15.5, width of umbilicus 3.9 mm., 44 whorls. 
A single specimen of this species was in the Newcomb collection 
with the type of M. rowelli; presumably from the same locality. 
It is not fully mature, yet should be easily recognized by the 
strongly depressed shape and large umbilicus, unlike any other 
known species of the region. It is more depressed and more openly 
umbilicate than M. rizfordi, which appears to be related. 
Type in the Newcomb collection, Cornell University. 
7 Mammals of the Mexican Boundary of the United States, Bull. 56 U. S. N. 
M., 1907, pp. 21, 122, pl. 13, fig. 1. 
8 The Old Yuma Trail. National Geographic Magazine, XII, 1901, pp. 129- 
143, map on p. 132. 
