FOSSIL HORSE REMAINS FROM IDAHO — GAZIN 283 



named by Cope ^ on the basis of fish remains collected by Clarence 

 King and others from exposures in the vicinity of Catherine and Castle 

 Creeks and were believed to be Pliocene in age. The earliest reports 

 on these fishes were made by Leidy * and Cope ® in 1870. Deposits in 

 the region generally referred to the Idaho formation probably com- 

 prise more than one horizon and apparently may be included within 

 the limits of upper Pliocene and lower Pleistocene. 



A collection of mammalian remains obtained by Clarence King 

 from Idaho beds exposed along Sinker Creek, a short distance to the 

 west of Castle Creek, included material identified by Leidy ^ as 

 representing Equus excelsus and Mastodon mirificus. Collections 

 made by N. F. Drake and others for Lindgren ^ v/ere obtained at 

 various localities, some of which may have come from deposits other 

 than the Idaho formation. Among these materials F. A. Lucas 

 identified Alastodon, Castor, Equus, Rhinoceros, Procamelus, Cervus, 

 and an antelope. An equid type in the collection was believed by 

 Marsh to represent Protohippus. A collection made by Russell ' 

 included a camel, an edentate, and fish remains, which Lucas con- 

 sidered to be of Pliocene age. 



Later, in 1917, Merriam ^ discussed the relationship of the Idaho 

 vertebrate fauna to other Pliocene assemblages, and in 1918 *° 

 he described tiiree new species from these beds, Ischyrosmilus idahoen- 

 sis, Neotragoceras lindgreni, and Equus idahoensis. In 1927, O. P. 

 Hay ^^ cited all the forms then Imown to occur in the Idaho formation 

 and possibly older beds together with those that came from later 

 river gravels, and the whole was considered of Pleistocene age, pri- 

 marily on the basis of materials coming exclusively from the stream 

 gravels of undoubted Quaternary age. 



OCCURRENCE AND PRESERVATION OF MATERIAL 



The great bulk of quarry material occurred in a lens of reddish, 

 bog-iron stained sand. Isolated bones and articulated skeletal portions 

 were found scattered through the lens but were most concentrated 

 near the bottom, lying near or on a more indurated limy layer, which 

 in places varies to a tliin gravel zone. The lens is iiregular in outline 

 but decidedlj^ concave upward in the north-south profile, resembling 

 a channel fill. The bog-iron staining suggests boggy conditions during 

 accumulation of the bones, but this may have been produced sub- 

 sequently by migrating waters, as even at present this channel above 



' Cope, E. D., Proc. Acad. Nat. Sci. Philadelphia, vol. 35, pp. 134-166, 1883. 



* Leidy, Joseph, Proc. Acad. Nat. Sci. Philadelphia, vol. 22, pp. 70-71, 1870. 



• Cope, E. D., Proc. Amer. Philos. Soc, vol. 11, pp. 538-547, 1870. 



« Leidy, Joseph, Proc. Acad. Nat. Sci. Philadelphia, vol. 22, p. 67, 1870. 

 ' Lindgren, Waldemar, 20th Ann. Kept. U. S. Geol. Surv., pt. 3, p. 99, 1900. 

 8 Russell, I. C, U. S. Geol. Surv. Bull. 199, p. 56, 1902. 



» Merriam, J. C, Univ. California Publ. Bull. Dept. Geol., vol. 10, pp. 431-434, 1917. 

 "i Merriam, J. C, Univ. California Publ. Bull. Dept. Geol., vol. 10, pp. 523-630, 1918. 

 " Hay, O. P., Carnegie Inst. Washington Publ. 322B, pp. 261-269, 1927. 



