Mollusca 129 



0. depressa is broader, more depressed or flattened, not so heavily 

 banded as some forms of cooperi. They look much alike yet can 

 be distinguished without much difficulty, and Pilsbry has shown 

 on anatomical grounds that they are certainly distinct species. 

 Unfortunately the anatomy of the typical 0. strigosa is unknown, 

 so that its relation with depressa has to be assumed from the 

 general appearance of the shell. Henderson notes that generally 

 speaking 0. depressa is more prevalent at lower elevations, as 

 along the foothills, though both it and cooperi go upward nearly 

 or quite to the timber line. In some localities, where conditions 

 are unfavorable, the shells are very small. The most famous 

 Oreohelix locality in Colorado is Glenwood Springs. Here we 

 find remarkable forms, differing on the two sides of the river. 

 On the north side of the river is 0. haydeni subspecies betheli of 



■,■;?*' 



Oreohelix depressa Ckll. Oreohelix cooperi 



W. A. Binney 



Pilsbry and Cockerell, a large flattened shell with numerous strong 

 spiral ribs or ridges; a very beautiful form. This was first brought 

 to my attention by Mr. E. Bethel, and when I later visited the 

 locality, I found that I had been within a few hundred yards of 

 it in 1887, but had never suspected the existence of the prize that 

 I so narrowly missed. The typical 0. haydeni came from Utah, 

 and is still known only from the lot originally collected. On the 

 south side of the river at Glenwood Springs, about the bases of 

 the dwarf oaks, we find a different snail, more globose, with 

 higher spire, and less sharply ribbed. This has been called alta 

 by Pilsbry, and on the mountain above the station for alta is still 

 another form, which Pilsbry named mixta. With all this com- 

 plexity in a small area, it is a question what may be found when 

 the whole country round about has been thoroughly searched. 

 There is here an excellent opportunity for the local naturalist. 

 Very rarely, specimens are found with the spiral reversed, the 

 aperture to the left instead of to the right, when the shell is viewed 

 from the side. No one knows the cause of this, but some genera 

 of snails (as the water-snail Physa, and the land-snail Clausilia) 



