282 PROCEEDINGS OF THE NATIONAL MUSEUM vol.83 



bringing them to the attention of Dr. Stearns. A small but interesting 

 collection of horse remains sent to the National Museum by Stearns 

 resulted in the Smithsonian Institution sending the late Dr. J. W. 

 Gidley to the locality in the following year and again in 1930. In 

 1931 the expedition was in charge of N. H. Boss, and the quarry 

 opened by Gidley was further developed and additional material 

 obtained. In 1934 I was permitted to continue the program in 

 southern Idaho in order to obtain a better representation of the asso- 

 ciated fauna from beds in the vicinity of the quarry and to make 

 another collection of horses. 



The principal quarry is located on the west slope of a hill or ridge 

 projecting southward from the desert rim into a deeply dissected 

 embayment (pi. 23, fig. 1). The hill is in T. 7 S., R. 13 E., Twin 

 Falls County, on the west side of the Snake River, opposite the town 

 of Hagerman. In addition to the main quarry several smaller quar- 

 ries and prospect holes were opened on the south and southwest slopes 

 of the hill and at about the same horizon, which is 55 to 60 feet or 

 more below the desert surface and a few hundred feet above the river. 



I am indebted to Dr. Alexander Wetmore and C. W. Gilmore, of 

 the National Museum, for encouragement in making this investigation 

 and to the staff of preparators in the division of vertebrate paleon- 

 tology for the excellent preparation and handling of the material. 

 Acknowledgment also is made of the courtesy extended by the staff 

 of the division of mammals of the National Museum in permitting 

 access to the collections of recent horses. Dr. Walter Granger, Dr. 

 Barnum Brown, and Dr. E. H. Colbert, at the American Museum of 

 Natural History, graciously aided in allowing me to examine and 

 measure mounted skeletons of Plesippus simplicidens and Equus 

 scotti, and Dr. C. L. Camp and R. A. Stirton, of the University of 

 California, kindly loaned me type material from the Pacific coast 

 region. The drawings were made by Sydney Prentice. 



PREVIOUS STUDIES IN SOUTHERN IDAHO 



Paleontological investigations of Neocene and Quaternary deposits 

 in the Snake River Basin have resulted in recognition of several hori- 

 zons of vertebrate life. The earliest of these terrestrial series is the 

 Payette formation, which apparently includes at least two faunal 

 horizons, the older being middle or upper Miocene ^ and the later 

 lower Pliocene.^ The Idaho formation, with which we are here more 

 concerned, is widely distributed over the western portion of the 

 Snake River Basin and is not easOy separated from the underlying 

 Payette in areas where the two are in contact. The Idaho beds were 



1 Chaney, R. W., Amer. Journ. Sci., ser. 5, vol. 9, pp. 214-222, 1922; and Oazin, O. L., Carnegie Inst. 

 Washington Publ. 418, pp. 37-86, 1932. 

 * Buwalda, J. P., Science, new ser., vol. 60, pp. 572-573, 1924. 



