650 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



glacial epochs of the Sierra Nevadas, though the climate is sup- 

 posed to have been only moderately humid and rather cold. 7'he 

 increase in the size of the lakes is not ascribed to the melting of 

 the glaciers, though this must have added considerably to their 

 volume, as the ice cap was not large enough to furnish so much 

 water. While Lake Lahontan seems not to have overflowed, 

 Lake Bonneville broke through the barrier to the north and 

 found an outlet to the sea by way of the Columbia River basin.^ 

 The desiccation of the lakes during the dry times is thought to 

 have been more complete than at present. 



The relation of our modern lakes to those of Pleistocene 

 times IS principally that of occupying the same area ; that is to 

 say, the bodies of water now existent have, in the main, been 

 formed since the old lakes dried up, and are not to be consid- 

 ered remnants left by incomplete evaporation, since in the latter 

 case the waters must have been much salter than they are. An 

 exception may perhaps be made of Great Salt Lake, the evi- 

 dence being inconclusive ; and I have no data of this nature 

 concerning Owens Lake and Mono Lake, which never formed 

 part of these two larger bodies, but were separate even during 

 the high-water periods of the Pleistocene. The littoral Fauna 

 may easily have been preserved, even through times of great 

 drought, by clustering about the edges of springs. In this way, 

 even to-day, we know that some are carried over ; for example, 

 this very Cicindcla echo flocks on the damp ground in the vicin- 

 ity of the little springs about the edge of the now dried-up 

 Humboldt Lake. Many springs are of a far more permanent 

 nature than the shallow lakes into which they discharge, and I 

 think that we may safely assume that they lasted, in many 

 through the times of most complete desiccation. 



i consider 

 been examined for n 



:rial for ' 



of existing lakes (which hav 

 ' paper), and those of 



times, in order to see what opportunity the beetles have had for 

 differentiation through isolation. I have visited Great Salt 

 Lake, Utah Lake, Humboldt Lake, Honey Lake, Walker Lake, 



