PUPILLA, AMERICAN. 161 



in the northern counties of Arizona, in Utah, and (as P. sub- 

 lubrica) in Nevada. 



Variation. 1. The typical form, about 3.2 to 3.3 ram. long, 

 ].5 wide, of 6y 2 to 6% whorls (pi. 19, figs. 4, 5, near Salt 

 Lake City, Utah) is widely spread in Colorado, eastern Utah 

 and New Mexico. The callus within the lip is moderate or 

 sometimes heavy. The crest behind the lip is well developed. 



In some localities there are wider shells: length 3.35, diam. 

 1.75 mm. North Park, Colorado. The rather thick lip-rib is 

 like typical blandi, the wide shell like form pithodes. 



There are also similarly wide shells (length 3.4, diam. 1.7 

 mm., Sapello canyon, N. M.) without an internally calloused 

 lip, being thus similar to form pithodes, though the parietal 

 fold is not so long. 



2. The prevalent or almost exclusive form east of the moun- 

 tains, from North Dakota to Texas, is small and compact, 

 about 2.5 mm. long, 1.5 wide, of 5i/o whorls, the lip often 

 quite strongly thickened. Cockerell has described it as 

 "Form obtusa. 2y 2 mm. long, broader in proportion to its 

 length than the type. Near the Micawber mine, Custer Co., 

 Colorado." It is probably a "hunger form" occupying arid 

 situations. It occurs in many places in Colorado, in New 

 Mexico, in the Rocky Mountains and along the Rio Grande, 

 mostly knowai from Pleistocene and river-drift examples. 

 Also in Arizona, from San Pedro river drift near Benson, 

 and in the northeastern counties. Some examples of this race 

 are hardly to be distinguished from P. sonorana; but the 

 latter appears to inhabit higher, less arid places than the 

 New Mexican blandi. 



In some cases longer shells, which would fall into typical 

 blandi, are in the same lots with form obtusa. 

 Cockerell has noted a mutation alba. 



3. Form pithodes Pils. & Ferr. (pi. 19, figs. 6, 7) is common 

 under and on dead wood in the forested zone, chiefly among 

 aspens, in the Black Range, between Grant and Sierra coun- 

 ties, New Mexico, 7,000-10,000 ft. ; also westward in the Mo- 

 gollon Mts., 9,500 to 10,000 ft,, and in Apache and Graham 

 counties, Arizona. It is wider than typical P. blandi, with a 



