EXPLORATIONS FOR FOSSIL HORSES IN IDAHO 



By NORMAN H. BOSS 

 Cliief Preparator, Department of Geology, U. S. National Museum 



Field operations in the vicinity of Hagerman, in the Snake River 

 Valley, Idaho, had demonstrated the fact that here was the greatest 

 accumulation of fossil horse remains ever discovered. Two seasons' 

 work under the direction of the late Dr. J. W. Gidley had brought to 

 light and added to the Museum's collection such a vast amount of 

 valuable material without exhausting the resources of the quarry that 

 a third season was deemed profitable. As the condition of Doctor 

 Gidley's health made it imprudent for him to undertake the strenuous 

 work of directing a party this year, I was detailed to take charge of 

 the 193 1 expedition. 



Arriving at Hagerman on June 4, I was joined by C. P. Singleton 

 of Melbourne, Fla., who had had previous experience with Doctor 

 Gidley ; C. W. Caldwell was employed as " handy man," and Charles 

 Bremer as cook, thus completing the personnel of the party. I wish to 

 say here that such success as attended the expedition was due in large 

 measure to their cooperation and understanding helpfulness. 



Camp established, the work of the season began by collecting such 

 specimens as were left from the previous year's excavations. It was 

 soon determined, however, that to work the deposit successfully other 

 means than pick and shovel would be necessary for removing the over- 

 burden of sand and gravel. Two weeks spent by the entire force in 

 stripping by use of plow and scraper resulted in exposing a portion 

 of the bone-bearing layer approximately 5,000 square feet in extent. 

 The magnitude of this task may be better understood when it is ex- 

 plained that the back wall of the excavation was 45 feet in height. 



This deposit of fossils is situated on the southern extremity of a 

 short, steeply sloping hill that juts out from the border of the plain. 

 Thus, as work progresses into the hillside, the depth of the overburden 

 above the fossil layer rapidly increases, for not only is the face of 

 the hill steeply inclined, but the bone horizon dips rapidly downward. 

 Resuming work with small tools on the ground uncovered, we found 

 fossil bones in great abundance (see fig. 37). Literally hundreds 

 of bones are present here, although disarticulated and widely scat- 

 tered, and nearly all pertaining to the extinct horse Plesippus 

 shoshonensis. However, 5 more or less complete skeletons, 32 skulls, 



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