overlook them without clear knowledge of the geographical area. For example, it is impossible to 

 identify ASinyaleamin Mountains or the exact location of O. alpina on this mountain or 

 McDonald Peak without a copy of Elrod=s (1902) description of his collecting trip. Third, 

 habitat requirements, especially for D. brunsoni , may be more narrow than previously appreciated. 



Information gleaned from Berry (1955) and Brunson (1956) suggests that D. brunsoni and O. 

 elrodi are sympatric in talus slopes on the north side of McDonald Lake. However, it may be that 

 both species co-occur in only a very restricted zone defined by the narrower habitat preference of 

 D. brunsoni . Evidence to date indicates that O. elrodi is significantly more widespread, even in 

 the McDonald Lake cirque. 



All three snail species favor exposed talus habitats. The type of talus in which each 

 species is found, however, appears to differ among species. Oreohelix alpina is found exclusively 

 above treeline in shallow limestone talus on mountain ridges. The descriptions provided by Elrod 

 (1901, 1902, 1903b) and Frest and Johannes (1995) agree generally to my findings in 1997. 

 Elrod ( 1 902) commented that the snails were found among and under rocks with little vegetation 

 nearby. All live individuals I located were under the protection of stones in areas of scant 

 vegetation cover, but usually with some soil and litter accumulation nearby. Ten (62.5%) of 16 

 live mdividuals that I could measure (one shell was broken during handling) were smaller than the 



minimum diameter (7 mm) described for this species (Elrod 1903b, Pilsbry 1939). However, size 

 range of empty shells found mostly on open ground closely matched the published range and 

 mean. Perhaps adults are more likely to be caught away from refuges in adverse conditions, and 



fatalities washed onto open ground. 



Discus brunsoni and Oreohelix elrodi are found well-below treeline in talus slopes 



10 



