DISCUSSION 



Extant populations of Discus brunsoni and Oreohelix alpina were located in 1997 at or 

 near the type localities 33 and 48 years, respectively, after the last documented collections (R. B. 

 Brunson pers. comm., T. J. Frest pers. comm.). The range in shell size of live individuals at each 

 site (including O. elrodi sites) indicates the presence of multiple cohorts and likelihood of 

 continuing reproduction. The sites where O. al pina was found on the southeast ridge of East St. 

 Marys Peak represent a slight range expansion at the type locality, where Elrod (1902) found 

 them on the southwest ridge. I have found no evidence that O. alpina has been collected on East 

 St. Marys Peak since 1900, when Elrod discovered the species. The last documented collection 

 of O. alpina (Brunson specimen catalog) was made on McDonald Peak on 2 August 1949. 

 Correspondence from Stillman Berry (21 August 1951: Brunson pers. comm.) indicates that 

 another collection may have been made on McDonald Peak in 1950 or 1951, but there is no 

 evidence of this in Brunson=s catalog. 



Several interacting factors probably contributed to the failure to find Discus brunsoni and 

 Oreohelix alpina during the last several decades. First, I know of no active resident collectors of 

 terrestrial mollusks. Non-resident collectors passing through the area may have visited sites when 

 conditions were not especially favorable for finding these species (D. brunsoni in particular) near 

 the surface of talus slopes. The nearly half-century span between first discoveries of O. elrodi and 

 D. brunsoni at the same site supports this contention. Differences in habitat selection may have 

 contributed to this lapse, as will be discussed below. Furthermore, it seems unlikely that very 

 many non-resident collectors would attempt to visit the relatively inaccessible localities of O. 

 alpina . Second, the known distributions of both species are quite restricted. It would be easy to 



