* PETERSON: A REVISION OF THE ENTELODONTIDA 47 
genre, une hauteur proportionnellement moindre de la couronne, et une plus grande 
largeur en arriére. Elle a, de plus, en avant et en arriére, des plis d’émail et des 
rugosités distinctifs. Si des découvertes ultérieures de piéces dentaires plus complétes 
venaient confirmir la valeur de ces caractéres, on pourrait imposer a cette nouvelle 
espécel’appellation d’entelodon Ronzonii, de la colline ot sont enfouies ses dépouilles.” 
Genus ARCH HOTHERIUM Leidy. 
In 1850 Dr. Leidy published a description of the first American forms of the 
family Hntelodontide under the name Archxotheriwm mortoni (40, pp. 93-94). 
Material of this genus which was subsequently collected from time to time by the 
early expeditions to the bad-lands of South Dakota and Nebraska was submitted to 
Dr. Leidy for study and was published by him in different publications under the 
generic names Arctodon (41, p. 278), Wntelodon (45, p. 392), and Archexothertwm. In 
1857 (48, p. 175) Leidy recognized Pomel’s name Hlotheriwm, which he continued 
to use for the American forms in different publications, including his work ‘‘ The 
Extinct Mammalian Fauna of Dakota and Nebraska.” On Plate IX, figs. 3 and 4, 
in “The Ancient Fauna of Nebraska” are illustrations representing a fragment of 
a skull which agrees quite perfectly with Leidy’s original description (40, pp. 92-93) 
and is undoubtedly that of the type. Other specimens figured and determined by 
Leidy as Archxotheriwm mortoni agree with a number of skulls, portions of skulls, 
and teeth in the Carnegie Museum, which were collected by the writer and others 
in the Titanotheriwm beds of the same general locality (Nebraska and South Dakota). 
The Oligocene of North America has yielded much material representing this genus, 
which is now scattered through the museums of America and Europe. 
Principal Generic Characters of Archeotherium: P* of relatively small size, 
with small internal tubercle; the crown triangular in outline; P+, 2, 2 separated 
by diastemata; lower molars with the anterior much higher than the posterior 
tubercles and separated by broad cross-valleys ; Pz separated from canine and Pz 
by diastemata ; occi pital condyles of proportional y small vertical diameter and no 
accessory facets on the basioccipital ; foramen ovale separated from foramen lac- 
erum ; dependent processes on the jugal and the inferior border of the mandible ; 
long alveolar border of the premaxillary and a long chin; limbs and feet propor- 
tionally long and slender ; trapezium present; magnum and unciform articulating 
slightly with one another at the dorsal border ; fibula free. 
Archeotherium mortoni Leidy. 
Type: A fragment of a skull with P* and P in place, and the alveolus for M2. 
Horizon: Oligocene (Titanotherium beds). 
