392 Charles Earle—Evolution of the American Tapir. 
the American Tapir. This discovery places the origin of the Tapir 
in America on a level stratigraphically with one of the species of 
Protapirus in Europe. We shall therefore expect that further 
discovery will perhaps prove the existence of the true Tapir in 
America, earlier than the Oreodon beds of the White River Miocene. 
Many authors have attempted to solve the problem of the origin 
of the Tapir in America. Professor Marsh! in 1877 held the view 
that the genus called by him Helaletes, was the ancestor of the true 
Tapir. Professor Scott? followed Marsh in deriving the Tapir from 
Helaletes (Desmatotherium). ; 
Prof. Cope*® was the first investigator to recognize that in the 
Wasatch and overlying Wind River beds, two types of Tapiroid 
superior molars were already then evolved. In the one, Systemodon, 
both external lobes are conical, and in the other Heptodon, the 
postero-external lobe is concave. This point is of great importance 
as shown by Prof. Osborn in tracing the ancestral history of these 
Perissodactyla. Prof. Osborn‘ in the “ Uinta Mammalia” re- 
moved Helaletes from the line leading to the true Tapirs, and placed 
Systemodon as the stem form of the latter. Later, Prof. Osborn® 
explained more fully his reasons for removing Helaletes from the 
Tapir line, and in this paper characterized the form of the superior 
molars in the three Tapiroid phyla of the Hocene. 
The recent discovery of Protapirus in America shows that this 
genus was represented by two species, one derived from a division 
of the White River Miocene (Oreodon beds), lower than the other 
(Protoceras beds). If we carefully compare the species of Protapirus 
figured by M. Filhol® with those found in America’ we will find 
a remarkably close resemblance in the characters of their teeth, and 
in fact it is quite difficult to separate the Protapirus obliquidens from 
the P. Douvillei of St. Gérand-le-Puy. 
In studying the early ancestors of the Tapirs in the Eocene of 
America, we observe certain differences in their foot-structure, and in 
the simplicity of the premolar teeth. These characters differentiate 
the early Tapirs from the later or true Tapirs. We notice first, 
that the earliest known Tapiroid, namely Systemodon, has the pre- 
molars less complex in structure than the true molars, and only-the — 
third and fourth superior premolars in this genus have internal 
cones. The upper true molars consist of two conical external lobes, 
which are of equal length transversely. This is a very important 
character in diagnosing the early Tapiride from the Rhinocerotide. 
lO. C. Marsh, Introduction and succession of Vertebrate Life in America, 
delivered before the American Association at Nashville, 1877. 
2 W.B. Scott, On Desmatotherium and Dilophodon, two new Eocene Lophiodonts, 
Bull. Princeton College, 1883, p. 46. 
3 K. D. Cope, The Perissodactyla, American Naturalist, 1888, p. 990. 
4 W. B. Scott and H. F. Osborn, The Mammalia of the Uinta Formation, Trans. 
Amer. Phil. Soc. 1889, p. 523. 
5 H. F. Osborn and J. L. Wortman, Fossil Mammals of the Wasatch and Wind 
River Beds, Bull. Amer. Mus. Nat. Hist. 1892, p. 124. 
6 H. Filhol, Reserches sur les Phosphorites du Quercy, 1877, p. 351. 
7 Ibid., Observations sur le memoire de M. Cope, etc., Ann. Sci. Geol. vol. xvii. 
art. 2. 
