PROTOHIPPUS. 



129 



PROCAMELUS-HIPPARION ZONE. 13. LOWER PLIOCENE. 



The typical exposures of this great zone along the Niobrara River and the Little White River contain 

 all the leading types or Protohippus, Pliohippus, and Hippahion of Leidy, Marsh, and Gidley. Geo- 

 graphically this zone is one of the most widespread of all the late Tertiaries. 



Hippodon speciosus Leidy 1S54. Gen. et spec, indet. 

 Text Fig. 101. 



Hippodon speciosus, Leidy, Joseph. [Remarks on Sus americanus, or Harlanus americanus, and on other extinct mammals], 

 Proc. Acad. Nat. Sci. Phila. Vol. VII, Pt. Ill, 1854, p. 90, no figure. "The Extinct Mammalian Fauna of Dakota and Nebraska," Jour. 

 Acad. Nat. Sci. Phila. (2) Vol. VII, 1869, pp. 320-321, pi. XIX, type, fig. 23, paratypes, figs. 19-22. 



Horizon and locality. — (Leidy) " Bijou Hill, east of the Missouri River, in a tertiary formation surmounting cre- 

 taceous beds." Bijou Hills, Brule Co., South Dakota. Type collected by "Meek and Hayden, during an expedition 

 to Nebraska Territory in the summer of 1853." Horizon probably Upper Miocene. 



Fig. 101. Original figure of type (fig. 23), Amer. Mus. Hall Coll. 465, and paratypes (figs. 19-22) of Hippodon spe- 

 ciosus Leidy, gen. et sp. indet. Natural size. After Leidy, 1869, PI. xix, figs. 19-23. 



Type. — Amer. Mus. Hall Coll. 465. A lower molar, either mi or m 2 of the right side, lacking the cement, and about 

 half worn. (Leidy, 1854, p. 90) " . . .an inferior molar of a solipedal animal." Leidy again referred to the type (1869, 

 p. 320) as follows: "The specimen of tlie last figure is from Bijou Hill, and appeared so peculiar that when first seen it 

 was viewed as indicating a new species, and was described in the Proceedings of the Academy for 1854, p. 90, under the 

 name of Hippodon speciosus. The specimens of the former figures [19-22] look so much like the latter as to render it 

 probable that they belonged to the same animal." 



Type figure — Text Fig. 101 of this Memoir. 



The genus Hippodon and species //. speciosus are indeterminate because the type and paratype lower molars figured 

 above show no distinguishing characters. The type certainly does not belong either to Hipparion or to Pliohippus. Its 

 characters are intermediate between a small Merychippus and a small Protohippus. In size it slightly exceeds Protohippus 

 placidus. The name becomes a nomen nudum because both generically and specifically the type is indeterminate. 



Protohippus perditus Leidy 1858. 



Plates 21.3, 25.S. Text Figs. 102, 103, 116a, 



Equus (Protohippus) perditus Leidy, 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 (sig. dated Apr., 1858), pp. 26-27, no 

 figure. Protohippus perditus, "The Extinct Mammalian Fauna of Dakota and Nebraska," Jour. Acad. Nat. Sci. Phila. (2) Vol. VII, 

 1869, pp. 275-277, PI. xvii, figs. 1, 2. 



Horizon and locality. — Niobrara River, near Fort Niobrara, Nebraska. Procamelus zone, Nebraska. Lower Plio- 

 cene. Type collected by F. V. Hayden, 1857. 



Type, — U. S. Nat. Mus. 019, cast Amer. Mus. 10772. (Leidy, 1858.) " . . a fragment of an upper jaw containing 



