THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 365 



of which (P. texanus), it is interesting to note, presents a close relationship 

 to the P. rex from the Rattlesnake Formation of Oregon. 



The horses are imperfectly known, but it is certain that they still be- 

 longed to the three great grazing phyla Pliohippus, Protohippus, and Neo- 

 hipparion, the browsing Hypohippus phylum having apparently disap- 

 peared, as well as the intermediate Merychippus phylum. One of the 

 species of Protohippus (P. cumminsii) was so progressive in character as 

 to have been referred by Cope to the genus Equus, but according to Gidley 



Fig. 170. — Carapace and tail of the Pliocene glyptodont Glyptotherium and skeleton of the 

 recent armadillo Xenurus. In the American Museum of Natural History. 



it shows a much closer relationship to the three-toed horse of the Miocene, 

 though it is more advanced than any true Miocene species of this genus. 

 The Pliohippus of this stage was also mistakenly referred by Cope to 

 Equus, but its principal characters point to a more primitive phase than 

 any true species of this genus. 



Glyplodonts. — Among the edentates, Glyptotherium is the only one 

 fully knowm. The existence of glyptodonts in Texas (1888) and Florida 

 (1889) was first made knowm by Cope and Leidy. A fuller knowledge of 

 these remarkable animals as they appear in the southern portion of the 

 United States was revealed in 1900 by the discovery by the American 

 Museum party under Gidley of a nearly complete carapace with tail arma- 

 ture of an animal found to be distinct from the South American glypto- 

 donts and thus described as Glyptotherium texanum by Osborn.^ This 

 animal was very primitive and simple in its tail structure, which strongly 

 suggests that of several of the Pliocene Santa Cruz types of Patagonia. 



' Osborn, H. F., Glyptotherium texanum. A New Glyptodont, from th(! Lower Pleistocene 

 of Texas. Bull. Arner. Mus. Nat. Hint., Vol. XIX. Art. .\%ii, pp. 491-494, Aug. 17, 1903. 



