Cope.) 62 [Feb. 17, 
On the Dicotyline of the John Day Miocene of North America. 
By H. D. Cope. 
(Read before the American Philosophical Society, February 17, 1888.) 
The number of species of peccary-like pigs whose bones are found in 
the John Day Miocene beds of Oregon has not been fully determined. 
Prof. Marsh first determined their existence in this formation, and named 
a species Dicotyles hesperius. He was followed by Leidy, who added 
Dicotyles pristinus. Marsh afterwards described two species under the 
names of Thinohyus lentus and 7. socialis. The present writer, at a still 
later date, added three species under the names of Chenohyus decedens, 
Thinohyus trichanus, and Palwocherus subequans. My present object is 
to endeavor to determine the relations of these species to each other and 
to species and genera of pigs already known. 
In the first place none of these species belong to the genus Dicotyles. 
Their premolars are quite distinct in composition from the true molars as 
in primitive mammalia generally. In Dicotyles the first in both jaws are 
identical with the true molars, or nearly so, and the preceding molars 
have internal tubercles, which the Miocene species do not possess. In 
Dicotyles there is also a preglenoid crest, which is wanting from the spe- 
cies in question. In all of these points the latter agree with Hyotherium 
von M. (Palwochwrus Pomel), of the Miocene of Europe. 
The full descriptions given by Gervais, and especially by Filhol, of this 
genus, enable the fullest comparisons with the American species to be 
made, at least as regards the cranial and dental characters. From these 
it results that the latter must be referred to one or more genera dis- 
tinct from Hyotherium. The principal distinction is seen in the develop- 
ment of the canine teeth in the American forms, and the adaptation of the 
opposed part of the cranium to the inferior canine. The canines are sub- 
triangular in section, and the inferior tooth is received into a deep fossa of 
the premaxillary and maxillary bones, as in Dicotyles. In Hyotherium 
no such fossa exists, and the canine teeth are of relatively small size and 
of ordinary form. The Oregon species represent one or more genera in- 
termediate in characters between Hyotherium and Dicotyles. 
Two generic names have been proposed for these animals—Thinohyus 
Marsh, 1875, and Chenohyus Cope, 1879. The former is distinguished 
by Marsh from Dicotyles as follows:* ‘‘The most noteworthy differences 
seen in the remains under description are, an additional premolar in the 
lower jaw, and the extension of the posterior nares between the last upper 
molars. The orbit is not enclosed behind, and there is no antorbital 
fossa. The brain was small, less than one-half the size of that of a Dico- 
tyles of the same bulk—and much convoluted. There is a strong bony 
tentorial ridge. The molar teeth have the principal cusps more isolated 
than in Dicotyles and the intermediate lobes larger.’’ It will be observed 
* American Journal Sci. Arts, 1875, p. 248. 
