90 



osborn: OLIGOCENE, MIOCENE, pliocene equid^e. 



short [subhypsodont] even when unworn; (4) enamel of crown and of ectoloph [m 3 ] covered with cement; (5) outer lobes 

 [paracone and metacone] with only a faint indication of the median ridge and their concave surfaces; (6) the buttresses 

 [para-, meso-, and metastyles] enclosing these faces are prominent; (7) metaloph ptychoid on both sides; (8) m 3 small; 

 (9) metaloph at an early stage of wear uniting with hypocone and not with hypostyle. 



(W. D. M. 1913) This is a progressive, heavily cemented, and relatively large species of Parahippus. The char- 

 acters enumerated above are shown in a somewhat less degree in the unworn teeth of other species of Parahippus. The 

 distinctions between unworn and worn teeth are very marked in this stage of evolution. 



(Osborn, 1918) This presents the closest approach to the Mcrychippus isonesus primus stage. 



Fig. 66. Parahippus brcvidens Marsh. (Right) Yale Mus. 11274, type, superior molars, m 2-3 , of the left side. (Left) 

 Referred molar, ?m 1 , in the collection of the University of California. All figures natural size. Left hand drawings by 

 B. Yoshihara, right hand by S. Oka. 



Parahippus crenidens Scott 1893. 

 Plates 8.4, 9.2. Text Fig. 67. 



Desmatippus crenidens sp. nov., Scott, W. B. "The Mammals of the Deep River Beds," Amer. Naturalist, Vol. XXVII, No. 319, 

 July, 1893, p. 661, no figure. "The Mammalia of the Deep River Beds," Trans. Amer. Philos. Soe., N. S. Vol. XVIII, 1894, p. 84, PI. 

 ii, figs. 9-14. 



Horizon ami locality. — Deep River valley, Montana, upper strata of the Deep River formation, Middle Miocene. 

 Type collected by Mr. I. Benet. 



Type — Princeton Mus. 10430 (cast Amer. Mus. 10782). (Scott, 1894, p. 84) "The type specimen of the new 

 genus consists of the dentition of both jaws, lacking the incisors, canines, first lower premolar and last upper molar, the 

 mandible, portions of the radius and ulna, femur, manus and pes, and fragments of other bones." Measurements: p'-m 3 

 .117; pi" 4 .068; m 1-3 .049. 



Type figure. — Text Fig. 67 of this Memoir. 



Characters. — (Scott, 1893, p. 661) "Posterior transverse crests of upper cheek teeth sinuous; limbs elongate and 

 slender; size moderate." Generic characters. (Scott, 1894, p. 84) Molars and premolars short crowned, the valleys 

 more or less filled with a thin deposit of cement. In the upper series the posterior transverse crest [metaloph] is connected 

 with the outer wall [ectoloph] and sends forward a process [crochet] which extends nearly to the anterior conule [proto- 

 conule]. Inner cusps of lower teeth expanded so as to narrow the entrances to the valleys. Median inner cusps (a, a 1 of 

 Rutimeyer) much more distinctly separated than in the older genera. 



From this clear description and the type figures may be added: (1) anterior enamel border in the region of the crochet 

 crenulate or ptychoid; (2) hypostyle triangular, well developed; (3) cingulum feebly developed on outer wall of p2-mi. 



