SUBALPINE 3IOLLUSCA. 7I 



Mr. Raymond's collection is of much interest, for sev- 

 eral reasons. It fills a gap in our knowledge of the sub- 

 alpine mollusca at a most important point, because the 

 most southern at which any are likely to be found up to 

 their highest limit, as determined by climate and favora- 

 ble topography. The more southern mountains, though 

 higher, are so much steeper and cut up by deeper canons, 

 through which torrents rush without intervening tracts of 

 meadow, or quiet lakes and ponds, that very few favor- 

 able locations for them can exist. Still further south 

 none but a few isolated peaks have snow upon them for 

 part of the summer, and the climate is so much drier that 

 the species of mollusca become limited to the vicinity of 

 the summits, except those native to the lower country, 

 and not subalpine. 



The only subalpine collections before made in the Sierra 

 were by myself in 1869, and by Mr. H. P. Carlton in 

 1870, between 5,000 and 7,000 feet elevation, near lati- 

 tude 39^^, as published in these Proceedings Vols. Ill to V, 

 and in Bulletin II, p. 358. In 1864 during a short visit 

 to Lake Tahoe I also obtained some species near the 

 south end of that lake, at the summit of Johnson's Pass 

 and at Strawberry Valley on the west slope, which were 

 partly described in the Proceedings, V^ol. Ill, 1868. 



As to vertical distribution, the highest elevations ob- 

 served for land shells were about 6,500 feet, and three 

 aquatic species were obtained at over 7,000 feet, or within 

 2,000 feet of perpetual snow, the ponds higher up con- 

 taining none. The land shells, however, show a differ- 

 ence of 3,200 feet greater elevation in latitude 39°, com- 

 pared with the perpetual snow, than in 38^, four identical 

 species being found on the east slope in both latitudes, 

 the Pisidiiiui on the other hand reaching 2,700 feet higher 

 toward the south. Suthcient facts on vertical range of 



