VERTEBRATE PALEONTOLOGY MATTHEW 281 



and Peterson in three fine memoirs, 26 and the excellent series of 

 Moropus skeletons obtained by the American Museum from the same 

 quarry provide a complete knowledge of this extraordinary animal. 

 Large collections have also been obtained from the Lower Miocene 

 for the Yale, Amherst, and Field museums. 



The later Miocene and Pliocene faunas are represented in the 

 Snake Creek quarries in Sioux County, Nebr., which have been 

 worked chiefly by the American Museum. 27 While the two great 

 fossil quarries mentioned above contain complete skulls and skeletons 

 of a limited number of large animals — three or four kinds in each — 

 the Snake Creek quarries contain chiefly fragmentary material of a 

 great variety of animals, no less than 50 genera being on my list at 

 present. They are river-channel pockets and are now known to 

 belong to three distinct faunal zones. 



Perhaps the most interesting out of a multitude of new forms 

 from these quarries are the upper tooth of an anthropoid primate, 

 Hesperopithecus, the first of this group from the American Tertiary, 

 and the complete skeleton of PUohippus, the earliest one-toed stage 

 in the evolution of the horse. Discovery by Troxell of fine skeletons 

 of Pliohippus 28 and of a Tertiary type of mastodon in the Pliocene 

 of South Dakota, and by Gidley of a large Pliocene fauna in Ari- 

 zona, should also be mentioned. 



The series of later Tertiary faunas discovered by exploring parties 

 from the University of California, on the Pacific coast and in the 

 Great Basin provinces, are a most important addition, as they are 

 almost wholly new fossil fields. 29 The material as yet discovered 

 is largely fragmentary, but a considerable series of faunas has been 

 differentiated. 



In the Pleistocene the great outstanding discovery is the La Brea 

 asphalt quarries near Los Angeles, remarkable for the numbers, the 

 variety, and the fine preservation of the specimens. The discovery 

 of this unique series makes it possible to describe the more character- 



x O. A. Peterson (1909) : Revision of the Entelodontidse. Mem. Carnegie Mus., vol. 

 iv, pp. 41-lu8, pis. liv— lxii ; 1910, Description of new carnivores from the Miocene of 

 western Nebraska, Ibid., pp. 205-278, pis. lxxiv-lxxxv ; 1920. The American Diceratheres. 

 ibid., vol. vii, pp. 399-476, pis. lvil-lxvi. 



W. J. Holland and O. A. Peterson (1914) : Osteology of the Chalicotheroldea. 

 Mem. Carnegie Mus., vol. iii, pp. 189—406, pis. xlviii-lxxvii. 



27 W. D. Matthew and H. J. Cook (1909): Bull. Amer. Mus. Nat. Hist, vol. xxvl, 

 pp. 361-415. 



W. J. Sinclair (1915) : Proc. Am. Phil. Soc, vol. liv, pp. 73-95. 

 W., D. Matthew (1918) : Bull. Amer. Mus. Nat. Hist., vol. xxxviii, pp. 183-229. 

 H. F. Osborn (1918) : Mem. Amer. Mus. Nat. Hist., n. s., vol. ii, p. 28; Amer. Mus. 

 Novitates, no. 37. 



28 E. L. Troxell (1916) : Am. Jour. Sei., vol. xlil, pp. 335-348. 



H. F. Osborn (1918) : Equidse of the Oligocene, Miocene, and Pliocene of North 

 America, iconographic type revision. Mem. Amer. Mus. Nat. Hist., n. s., vol. 11, p. 162, 

 pis. xxviii-xxx. 



*» J. C. Merriam and others (1910-1922) : Univ Calif. Geol. Publ., numerous contribu- 

 tions. 



