112 BULLETIN UNIVERSITY OP MONTANA 



fishing and beautiful scenery- There is no drift around the shores, most 

 of the drift having lodged in the outlet. Here there is a quite a jam. 



CONCHOLOGY OF McDONALD LAKE. 



Search was made daily for shells. In the waters there were large 

 numbers of a new variety of Limnaea emarginata Say, described in Nau- 

 tilus, Vol. XV,* as var. montana. This is the same shell that was pre- 

 viously taken in Sinyaleamin lake with so much labor, and was much 

 more aboundant in McDonald like than in Sinyaleamin. Along the 

 rocks in the middle of the lake they were taken in considerable numbers, 

 and at the outlet others were taken among the grass and weeds in the 

 shallow water. This species seems to relate emarginata to stagnalis, 

 some of the shells showing the malleations of stagnalis quite 

 plainly. Placed side by side they have many points in common, 

 but are very much smaller than the variety appressa of stagnalis taken 

 in western Montana. 



Physa ampullacea Gld. was found sparingly, not so abundant as in 

 Sinyaleamin lake. Strange to say, not a single specimen of Planorbis 

 was seen. Planorbis seems to be a warm water species, and while a few 

 were taken at Sinyaleamin lake, they were very scarce, and the few 

 taken were small and badly broken. In the small ponds and lakes in the 

 valley to the west of the Mission range Planorbis trivoivis is exceedingly 

 abundant, and in the small lakes or ponds of glacial origin along Flat-- 

 head lake these shells are found in gi'eat numbers. 



Among the underbrush at the lower end of the lake Pyramidula stri- 

 gosa var. Cooperi was found in large numbers, as also P. solitaria Say. 

 These two species have been considered distinct heretofore. A large 

 series of several hundred was assorted with the attempt to make two 

 species. The most widely different were easily separated, but by this 

 process of elimination those remaining were more and more difficull; 

 to place in one species or the other, and the last remaining could appar- 

 ently go as easily in one pile as the other. From external appearances 

 it seems difficult to distinguish some of those found at this lake as be- 

 longing to either the one or the other species. The two were found in 

 the same locality, were picked up together, and were placed in the sama 

 receptacle. It was impossible to do anything toward working out life 

 histories, and internal anatomy may reveal differences that external 

 anatomy does not disclose. But as descriptions of shells are largely 

 based on external anatomy it is doubtful if these two species are distinct. 

 It may be well to note here that all the shells taken so far at the upper 

 end of Flathead lake are var. cooperi, none having been taken that could 

 be called solitaria. 



Having found a very small variety of the shell Pyramidula strigosa, 

 called alpina, at high altitude on Sinyaleamin mountain, it was thought 

 the same shell might be found on the heights of McDonald peak. A short 

 description of the trip in search for this shell is given in the succeeding 

 pages. Sinyaleamin mountain is almost due south of McDonald peak, 

 in the same range, the distance between the two peaks in air line being 



* Nautilus, Vol. XV., p. 111. 



