120 



OSBORN: OLIGOCENE, MIOCENE, PLIOCENE EQUIDiE. 



Horizon and locality. — (Douglas, p. 274) " These beds form a part of the bluffs along the eastern side of the Missouri 

 River north of Confederate Creek and east of Winston in Montana. The type was collected by Earl Douglass and Ray 

 Roberts in 1902." 



Type. — Carnegie Mus. 905. (Douglass, p. 274) "The type of this species is a portion of a skull, a mandible, a radius, 

 two femora, two complete and two incomplete metapodials, also numerous fragments." Measurements: (Douglass, 

 p. 274) dp 1 ^ .0842; m 1 a.p. .022, tr. .021; m 2 a.p. .021. 



Paratype. — From the same locality, only a few feet away, a nearly complete hind foot, Carnegie Mus. 858, was 

 obtained. This undoubtedly belongs to the same species as the type, and the age of the two individuals was nearly the 

 same, as shown by corresponding portions of mandibles with teeth. 



Type figure. — Text Fig. 93 of this Memoir. 



Characters. — (Douglass, p. 274) (1) Lachrymal fossa long and moderately deep; (2) malar pit with steep posterior 

 side, bounded below by a thin, shelf-like malar-maxillary ridge. (3) Temporary molars brachyodont or brachy-hypsodont; 

 (4) permanent molars curved and strongly hypsodont ; (5) both series of teeth with a coating of cement which is not very 

 thick; (6) enamel lakes simple with only one or two simple enamel folds on each; (7) protocone and hypocone laterally 

 compressed, the former separate from the protoconule but having an angular projection toward the latter; (8) first tempo- 

 rary lower molar minute; (9) intermediate external conule on lower temporary molars concave on the inside, more or less 

 flattened on the outside. (10) Metapodial nearly ninety per cent, of the length of the radius and eighty-four per cent, of the 

 length of the femur exclusive of the proximal epiphysis. 



(Matthew, 1913) The deciduous premolars are moderately high-crowned. This general type is difficult to dis- 

 tinguish from M. isonesus Cope, with which it agrees in size. 



PROCAMELUS-MERYCHIPPUS CALAMARIUS ZONE. 11. LATE UPPER MIOCENE. 



This zone is distributed in California and New Mexico. It is typified at Barstow by the presence of 

 progressive species of m ehychippus, such as m. calamaiuus cope. 



Merychippus sumani, n. sp., Merriam, John C. "New Horses from the Miocene and Pliocene of California," Univ. Calif. Publ. 

 Bull. Dept. Geol. Vol. 9, No. 4, Nov. 22, 1915, pp. 49-50, fig. 1. 



Fig. 94. . Original figure of the type of Merychippus sumani Merriam, Univ. Cal. Pal. Coll. 21422, p 4 -m 3 . Natural 

 size. After Merriam, 1915, fig. 1, p. 51. 



Horizon and locality. — Barstow, Barstow formation, Upper Miocene, Mohave Desert, California. Type collected 

 by John R. Suman. 



Type. — Univ. Cal. Pal. Coll. 21422. Series of upper molars of the right side, p 4 -m 3 . Measurements: m'-m 3 .057; 

 p 4 a.p. .022, tr. .0208; m 1 a.p. .019, tr. .0194, height of crown .0285. 

 Type figure. — Text Fig. 94 of this Memoir. 



Characters. — (Merriam, 1915) " Upper cheek-teeth much smaller than in typical Merychippus calamarius or in 

 M. intcrmontanus. Crowns of cheek-teeth considerably elongated, markedly curved, and well cemented; height of the 



Merychippus sumani Merriam 1915. 



Text Fig. 94. 



