PLIOHIPPUS. 



165 



Type. — Amer. Mus. Cope Coll. 8183, a left superior molar, m 2 , and an associated or referred upper premolar, p 2 . 

 (Cope, 1880, p. 223) "It is represented as yet by superior molar teeth only." Measurements: (Cope, 1880) second 

 premolar a.p. .035, tr. .021, height of crown .035; m 2 a. p. .027, tr. .027, height of crown .045. 



Type figure. — Text Fig. 132 of this Memoir. 



Characters. — (Cope, 1880) (1) Molar teeth of larger size than those of any of the extinct American horses excepting 

 Equus excelsus, about equalling those of Hippidium neogceum Lund; (2) crowns very long, slightly curved; (3) roots 

 short; (4) internal columns [protocone, hypocone] relatively small, subequal in size, flattened in outline; (5) fossettes of 

 great transverse width, equal to the anteroposterior diameters; (6) crescents [pa, me, pi, ml] correspondingly narrow; 

 (7) enamel borders of fossettes simple, there being only a few notches on the adjacent faces; (8) one loop [pli caballin] 



Fig. 132. (Upper) Original figure of the type of Pliohippus (Hippidium) spectans Cope, Amer. Mus. 8183. (a) 

 Crown view of superior molar, (6) incisive surface of crown showing coating. Natural size. After Cope, 1887, fig. 41, p. 

 1972. (Lower) Type of Pliohippus spectans Cope, Amer. Mus. 8183, left superior molar, m 2 , and associated or referred 

 upper premolar, p 2 of the right side. External and interior views of nr. Natural size. Drawings by S. Oka. 



projecting from inner enamel border almost reaching anterior inner column [protocone]; (9) cement abundant; (10) a 

 crochet fold projecting into prefossette. 



Matthew observes (1913): "This species belongs to the group characteristic of the Pliocene, larger animals with large 

 fossettes, little complication of enamel, very heavy mesostyle and parastyle, and long-crowned teeth, strongly curved. 

 Protocone strongly united to protoloph, small, oval, anterior in position. Fossettes broad with almost no plications." 



Pliohippus coalingensis Merriam 1914. 

 Text Figs. 133. 



Protohippus coalingensis, Merriam, John C. " Correlation between the Tertiary of the Great Basin and That of the Marginal, 

 Marine Province in California," Science, N.- S. Vol. XL, No. 1035, Oct. 30, 1914, p. 644, no figure. Pliohippus coalingensis, " Tertiary 

 Vertebrate Faunas of the North Coalinga Region of California," Trans. Amer. Philos. Soc. N. S. Vol. XXII, Pt. Ill, Nov. 10, 1915, 

 p. 230, figs. 29a, 29b. 



