382 



SCIENCE 



[N. S. Vol. XXVI. No. 664 



for the study of extinct mammalian faunas 

 than Las yet been discovered elsewhere in 

 Nevada. Situated as they are between the 

 typical localities of the Tertiary formations 

 of eastern Oregon and the areas of Truckee 

 Miocene in Nevada, they will probably be the 

 key to the correlation of these formations. 

 The examination of the beds made thus far 

 has necessarily been exceedingly superficial, 

 but it is hoped that the continuation of this 

 work during the next season will put us in a 

 position to make a satisfactory determination 

 of the relative ages of the Oregon and Nevada 

 Tertiary formations. 



John G. Merriam 

 Univeesitt of California 



physiographic changes bearing on the 



faunal relationships of the russian 



and sacramento rivers, 



california 



For some time biologists in this state have 

 noted the close relationship between the fauna 

 of the Russian River and that of the Sacra- 

 mento, in forms that do not migrate through 

 salt water. In a recent trip through Lake 

 County very clear evidence was found that 

 the waters of the Scott's Creek now flowing 

 into Clear Lake and thence into the Sacra- 

 mento, formerly flowed into the Russian 

 River. Clear Lake is a sheet of water some 

 twenty miles in length and lying at an eleva- 

 tion of about thirteen hundred feet in the 

 middle of Lake County. Scott's Creek rises 

 in the mountains to the westward and after 

 flowing to within two miles of Clear Lake 

 turns to the northwest, cutting a gorge 

 through the mountains. 



On going down this valley one is confronted 

 by the ' startling physiographic fact that it 

 bifurcates into two valleys without change of 

 grade. Such a division is not unusual on the 

 flat surface of a low-grade delta, but it chal- 

 lenges investigation when encountered in a 

 mountain gorge with hills rising fully a 

 thousand feet on both sides. The valley to 

 the left has practically a level floor and is 

 occupied by the narrow and rather deep Blue 

 Lakes. Three miles from where it leaves 



Scott's Creek, without any narrowing it termi- 

 nates abruptly against a transverse ridge about 

 one hundred and sixty feet high. Beyond 

 this ridge the valley is occupied by Cold 

 Creek, which empties into the Russian River. 



Returning to the point of bifurcation of" 

 Scott's Creek the gorge to the right turns east- 

 ward and empties into the northern end of 

 Clear Lake. 



Climbing the hills on either side of Blue 

 Lakes the valley in which they lie is seen 

 to be continuous in slope and outline with that 

 of the upper portion of Scott's Creek and of 

 Cold Creek except for the low transverse ridge 

 already mentioned and which evidently is the 

 dam that made Blue Lakes. 



On examination this ridge is clearly a com- 

 paratively recent landslide. It has the char- 

 acteristic hununocky, uneven surface and still 

 shows two or three ponds not yet fllled nor 

 drained. The slide came from the southwest 

 slope of the main valley and is approximately 

 a mile in length, starting from an elevation of 

 fifteen hundred feet (aneroid) above the Blue 

 Lakes. The valley is here about an eighth of 

 a mile in width, and the momentum of the 

 slide carried it across the valley and some- 

 what up the opposite slope. At this point, 

 which is crossed by the stage road to Ukiah, 

 the contrast in color of soil of the slide and of 

 the eastern valley slope is very marked. 



When the slide occurred the waters of 

 Scott's Creek were evidently backed up for 

 some ten miles, forming a lake, narrow in the 

 gorge and widening out in the more open 

 valley above. The waters of this new lake 

 rose until they overflowed a low divide sepa- 

 rating a tributary from the head of a small 

 tributary of Clear Lake. The outlet thus de- 

 termined was lowered by erosion and is now 

 the main channel of Scott's Creek. The base 

 level for this channel was determined by Clear 

 Lake and the lake in Scott's Valley was soon 

 filled by sediment making a rich alluvial plain 

 with a maximum width of two miles. In a 

 well sunk in the center of this plain tules 

 were found at a depth of about seventy feet 

 below the present surface. The portion of the 

 old channel below the tributary through which 



