MAN AND THE LAVA BEDS. 705 



Latia dalU White, Sphoerium idahoensis Meek, and S. negosum 

 Meek. 



These are found in consolidated gravel 100 feet beneath 

 a thick capping of lava. The elevation of the lava here is 

 400 feet above that at Nampa, 85 miles farther down the 

 river. According to Dall these sedimentary rocks belong to 

 Cope's " Idaho Lake," and are "very likely middle or later 

 pliocene. Both the unconsolidated character of the Nampa 

 beds and the lower level at which they occur indicate a pleisto- 

 cene age. They occur in a basin which has either been eroded 

 out of Pliocene deposits synchronous with those at Glens 

 Ferry, or in one formed by uneven elevations of land of which 

 we have no definite record. The rapidity with which the 

 deposits at Nampa were formed appears from their character. 

 One of the beds of quicksand was 100 feet thick and two other 

 40 and 30 respectively. For 70 miles below Nampa there are 

 no superficial lava beds, while there at the Oregon line, the 

 Snake River Valley becomes very much constricted, and con- 

 tinues in a narrow gorge for a long distance. The situation 

 furnishes just such conditions as would favor the rapid 

 accumulation of fine sediment naturally brought down by 

 such debacle from Lake Bonneville as is known to have taken 

 place in pleistocene or glacial times. With respect to the 

 age of the lava deposits it is also to be said that all observers, 

 (especially Hayden and Russell) call frequent attention to 

 outflows of lava in various parts of the Snake River Valley 

 that are very recent — some of them not more than two or 

 three centuries old. We, therefore, are amply justified in 

 connecting the Nampa figurine with deposits of glacial age. 



