MIOHIPPTJS. 



63 



Characters. — (Matthew, 1913) (1) About one-seventh shorter and with a muzzle relatively more slender than the 

 type of M. equiceps. (2) Dentition about one-seventh smaller than that of M. equiceps; (3) molar teeth relatively wider 

 transversely than in M. equiceps or M. brachylophus; (4) no internal eingulum; (5) m 3 relatively smaller than M. equiceps 

 or M. brachylophus; (6) incisors of smaller size; (7) canines of much smaller size than in M. equiceps, possibly a sexual 

 character. (8) Infraorbital border of orbit above anterior part of m 2 . 



Referred to this species by Matthew is the anterior portion of a skull, Amer. Mus. 7276. Of doubtful reference are 

 lower jaws associated with fragments of the skeleton, Amer. Mus. 7274, 7293. 



PROMERYCOCH(ERUS-MIOHIPPUS ZONE. 7. LOWER MIOCENE. 



This zone is typified in the Upper John Day beds of Oregon and is widely distributed in western Nebraska, 

 South Dakota, and Montana, as described above. Besides abundant Miohippus, it includes Kalobatippvs 



AND THE MOST PRIMITIVE SPECIES OF PaRAHIPPUS. 



Miohippus condoni Leidy, 1S70. Spec, indet. 

 Plate 3.12. Text Fig. 42. 



Anchitherium condoni, Leidy, Joseph, [Collection of fossils from valley of Bridge Creek, sent by Thomas Condon] Proc. Acad. 

 Nat. Sci. Phila., Vol. XXII, 1870, p. 112, no figure. "Contributions to the Extinct Vertebrate Fauna of the Western Territories," 

 Report U. S. Geol. Sure. Terr., F. V. Hayden, U. S. Geologist in charge, Vol. I, Ft. I, 1873, p. 218, PI. ii, fig. 5. 



5 



Fig. 42. Original figure of the type of Miohippus condoni Leidy, Acad. Nat. Sci. Phila. Coll., deciduous premolar, 

 dp 3 . Natural size. After Leidy, 1873, PI. ii, fig. 5. 



Horizon and Locality. — Upper John Day. "... valley of Bridge Creek, a tributary of John Day's River, Oregon." 

 Collected by Thomas Condon. 



Type. — A broken upper molar, apparently dp 3 . 

 Type figure. — Text Fig. 42 of this Memoir. 



Characters. — The species is indeterminate from the type, which is apparently a deciduous third upper premolar. The 

 genus is undoubtedly Miohippus. The size is about the same as M. annectens and M. anccps. The relative breadth of 

 this tooth is due to its being a deciduous premolar. The hypostyle has one of the typical Miohippus forms of a crest 

 parallel to the posterior eingulum. 



Miohippus annectens Marsh, 1874. 



Plate 3.14,15. Text Fig. 43. 



Miohippus annectens, gen. et sp. nov. "Notice of New Equine Mammals from the Tertiary Formation," Am. Jour. Sci. and Arts 

 (3), Vol. MI, No. 39, Mar., 1874, p. 249, no figure. 



Horizon and locality. — "Miocene of Oregon," John Day formation, probably Upper John Day, Promerycochcerus 

 zone. (Lull, R. S., letter Oct. 9, 1915) "J/, annectens, however, is in a gray matrix which we have always considered as 

 Upper John Day." Type collected by 0. C. Marsh, November 1, 1871, from John Day River, Oregon. 



Type. — Yale Mus. 11275. Type specimen not designated in original description. (Lull, R. S., letter Oct. 23, 1915): 

 "Miohippus annectens is based upon three distinct specimens only one of which is marked type; this is catalogue number 



