94 



OSBORN: OLIGOCENE, MIOCENE, PLIOCENE EQUIDjE. 



of larger size and probably a distinct species, consequently the above species characters (5 and 6), based by the author 

 on these particular teeth, are invalid. 



The characters presented in these teeth indicate a species of Parahippus somewhat more advanced in development 

 than P. crenidens, and decidedly more specialized than P. pawniensis. 



A/o. 9040 Type 

 A. M. 



Fig. 70. Type of Parahippus coloradensis Gidley, Amer. Mus. 9040, m 3 of the left side, m 2 of the right side. Natural 



size. 



PROCAMELUS-HIPPARION ZONE. 13. LOWER PLIOCENE. 



This zone is typified by the exposures near Fort Niobrara, Nebraska, and is widely distributed in the 

 western United States. It contains the final stages of Parahippus. 



Parahippus cognatus Leidy 1858. 



Plates 8.8, 9.5, 25.2. Text Fig. 71. 



Anchitherium {Parahippus) cognatus, Leidy, Joseph. "Notice of Remains of Extinct Vertebrata, from the Valley of the Niobrara 

 River, collected during the Exploring Expedition of 1857, in Nebraska, under the command of Lieut. G. K. Warren, U. S. Top. Eng., 

 by Dr. F. V. Hayden, Geologist to the Expedition," Proc. Acad. Nat. Sci. Phila., Vol. X, 1858, p. 26, no figure. Parahippus cog- 

 natus, "The Extinct Mammalian Fauna of Dakota and Nebraska," Jour. Acad. Nat. Sci. Phila. (2) Vol. VII, 1869, p. 314, PI. xxi, figs. 

 7-10. 



Horizon and locality. — Niobrara River near Ft. Niobrara, Nebraska. Probably Procamelus zone, Lower Pliocene. 

 Name of collector not given. 



Type. — U. S. Nat. Mus. 567 (cast, Amer. Mus. 10772). Three upper milk molars of the left side, dp 2,3,4 , also dp2. 

 (Leidy, 1869, p. 314) "The teeth all belonged to the same individual, and appear to pertain to the temporary series. . . 

 The specimens consist of the upper molar teeth of the left side and the first lower molar of the right side." Measure- 

 ments: (Gidley, 1907, p. 881) dp 2 a. p. .025, tr. .018; dp 3 a. p. .019, tr. .020; dp 4 a. p. .020, tr. .020. 



Type figure. — Text Fig. 71 of this Memoir. 



Characters. — (Leidy, 1858, p. 26) (1) The premolar teeth of the same form as the upper deciduous molars of Meso- 

 hippvs (Anchitherium) bairdii or A. aurelianense except that the outer extremity of the prolongation of the postero- 

 internal lobe [metaloph] branches into several short [crochet] folds. These latter have the same arrangement as the 

 smaller but more numerous folds in the same position in Mcrychippus. 



(Gidley 1907, p. 881) (1) Milk teeth brachyodont; (2) cement thin or wanting; (3) inner cones [pr, hy] larger than 

 median conules [pi, ml]. 



