HIPPARION. 



183 



Paratype. — • (Gidley, 1906, pp. 148-151) Amer. Mus. 10S32. Complete lower jaws with full dentition and an 

 associated upper molar, m 2 . Measurements: (Gidley, 1906, p. 151). 



Measurements of Paratype (Amor. Mus. 10832) 



Diameters of m 2 , anteropost 021 transv 021 



Total length of jaw 352 



" " " molar-premolar series 138 



Type figure. — Text Fig. 145 of this Memoir. 



Characters. — (Gidley, 1906, 1907) (1) About equal in size to Hipparion affine Leidy; (2) differing from II. affine in 

 (a) the more open fossettes of the upper teeth, (b) the greater complexity of the enamel foldings, (c) the proportionately 

 smaller and more rounded protocones; (3) differing from //. occidentale Leidy in (a) its smaller size, and (b) in the different 

 proportions of the premolars, which are relatively broader transversely; (4) differing from //. whitneyi Gidley in (a) its 

 smaller size, (b) in the greater number of folds in the enamel walls of the metaloph in the upper teeth, (c) the more open 

 fossettes, (d) the more rounded form of the protocones, (e) in the extreme forward position of the infraorbital foramen, 

 which is placed directly above the space between p 2 and p 3 , while (f) the masseter ridge extends but little farther forward 

 than in //. whitneyi. (5) The jaw is much longer and more slender than in II. whitneyi or in other known Miocene species 

 of horse; (6) the preorbital portion of the skull also is proportionately longer than the average of a dozen specimens of 

 Equus caballus examined by the author. 



Hipparion coloradense sp. nov. 

 Text Fig. 146. 



A/o. 9 0 9^f- Type 

 A M. 



Fig. 146. Hipparion coloradense Osborn, Amer. Mus. 9094, superior grinding teeth of the type, m l , m 2 of the left 

 side (reversed in drawing). Natural size. 



Horizon and locality. — Sand Canon, head of Pawnee Creek, Upper Pawnee Creek beds, Logan County, Colorado. 

 Procamelus-Hipparion zone, Lower Pliocene. Type collected by Maxwell of the American Museum expedition of 1898. 



Type. — Amer. Mus. 9094. Upper grinding teeth, m 1 " 2 , of the left side, ulna, radius, and hind foot. 



Referred specimens, Amer. Mus. 9115b, portion of hind foot, Amer. Mus. 9098, upper and lower teeth from Sand 

 Canon, Pawnee Creek, upper Pawnee Creek beds, Amer. Mus. 9384, lower jaw, from ten miles west of Grover, Colorado. 



Type figure. — Text Fig. 146 of this Memoir, 



