HIPPARION. 



191 



PLIAUCHENIA-PERACER AS -HIPPARION INGENUUM ZONE. 14. LOWER PLIOCENE. 



This zonk represents the second phase of the Lower Pliocene. 



Hipparion ingenuum Leidy 1885. 

 Text Fig. 154. 



Hippotherium ingenuum, Leidy, Joseph. "Rhinoceros and Hippotherium from Florida," Proc. Acad. Nat.Sci. Phila. Vol. XXXVII, 

 1885 (sig. dated Apr. 7, 1885), p. 33, text fig. p. 33. 



Fig. 154. (Left) Hipparion ingenuum Leidy, U. S. Nat. Mus. 3306, original figure of one of the two type molars, 

 m 2 of the left side. One and one-half natural size. After Leidy, 1885, p. 33. (Right) Type specimens, drawn under the 

 direction of Osborri by B. Yoshihara. (Centre figures) Crown, external, and anterior views of type molar, U. S. Nat. 

 Mus. 3306. Osborn figures natural size. Note: original figure is viewed in line of the axis of the tooth, the new figure 

 is viewed at right angles to the grinding surface; hence the difference in proportions. 



Horizon and locality. — (Leidy) The Alachua clays, or Archer beds of Archer, Florida. Upper Miocene or Lower 

 Pliocene (fauna of same age as that of the Republican River formation of western Kansas). Type collected by J. C. 

 Neal. 



Type. — U. S. Nat. Mus. 3306. (Leidy) Two superior molar teeth of the left side. Measurements: (Gidley, 

 1907) m 2 a.p. .0185, tr. .0165, height of crown .043 outside, .034 inside. 

 Type figure. Text Fig. 154 of this Memoir. 



Characters. — (Leidy, 1885, Gidley, 1907) (1) An animal little more than half the size of the domestic horse, E. 

 caballus. (2) Foldings of the metaloph within the pre- and postfossettcs, four anterior, three posterior; (3) single anterior 

 and posterior folds in pre- and postfossette respectively; (4) prominent crochet fold and pli caballin; (5) internal islet 

 [protocone] elliptical instead of circular. (Gidley) (6) An animal little larger than the type of //. venustum Leidy; (7) 

 differing from //. venustum only in the characters pointed out by Leidy, which are slight and of little value. (8) Widely 

 separated in size, in the form of the protocone, and in the enamel plications from //. montezuma. 



