BIOLOGICAL RECONNOISSANCE AT FLATHEAD LAKE. 115 



forms will be found which will destroy the identity of the species is to 

 he determined. During our stay of ten days at McDonald lake several 

 days were spent almost entirely in searching for both living and dead 

 specimens. More minute descriptions of the results of this search hava 

 been given elsewhere, and need not here be repeated. It is suf- 

 ficient to say the living shells were found. The first were taken 

 high up, on a small space on the top of a crag where there was a little de- 

 caying rock, while trying to get a good position for a photograph of the 

 peak opposite. The success on this occasion spurred to greater effort, 

 resulting in finding other living shells nearer the water's edge, by going 

 deep among the talus toward moisture. But none living were found 

 among the rocks close to the lake. The net results of this search were 

 several quarts of shells, with several dozen preserved animals, some of 

 them beautifully expanded. 



This shell, Pyramidula eirodi Pils., appears to have a very limited 

 range. It is found abundantly on the northern shores of the lake west- 

 ward to the last stream of water trickling over the rocks, when it ceases 

 abruptly. On the southern shore of the lake it is found very sparingly, 

 but a few being found as the result of an afternoon's search, among them 

 a single live one. There is good reason for believing they occur along 

 the slopes of the mountains that form the amphitheater above the lake, 

 bordering the valley mentioned, as otherwise their presence on the south 

 side of the lake is not accounted for. They have been found up on the 

 side of the mountain as far as explorations have been made, up to 7,500 

 feet, and still seem to continue. How far up the mountain they are 

 to be found is problematic, and should be determined. Diligent search 

 has so far not revealed the species at any other part of the Mission range. 

 It is expected later to make collections on the east side of the range, 

 when search will be made for the shell there. Search for shells during 

 succeeding years has failed to produce a single speciment from other 

 localities than the one here described. The distribution therefore seems 

 to be extremely limited. The amphitheater may better understood by 

 consulting Plate XXIX. 



The shell is not only a land form, but is a rock form. It seems to 

 have a preference for nooks and crevices on the summit of some cliff. 

 In searching for them it was discovered they were most abundant along 

 the water courses, where vegetation had not yet gained a foothold. It 

 was unnecessary to search among the debris collected at the roots of a 

 clump of bushes, but if there was an open space where the talus was 

 loose and open they were likely to be found. In the spring time they 

 evidently crawl over the brown lichen covered rocks in search of the 

 lichen food, crawling beneath when the warm days come on and the 

 moisture on the rocks dries up. The few remaining too long are killed, 

 their shells bleaching from a dark flesh brown to a beautiful pearly white. 

 It is described by an admiring friend as the queen of the Pyramidulas. By 

 digging among the damp talus a few live ones may be found. Higher 

 up, where there are small springs from the mountain side, they may also 

 be found. 



During the season of 1901 a week was spent again at McDonald lake 



