PETERSON : A REVISION OF THE ENTELODONTIDA 145 
mand, were constrained to place it among the living swine, where it has since, with 
only one or two exceptions (Subursi of de Blainville and Arctodon of Leidy), gener- 
ally been placed by different writers. That the family is a “collateral branch” of 
the Suide, which “ branched off in early Eocene time” as Marsh says (64, p. 406), is 
from all the evidence at hand unquestionable. ‘Schlosser has referred the genus 
[ Elotheriwm] to the bunodont division of the family Anthracotheriidx, which family he 
derives from an Eocene stock common to the Anthracotheriidx, the Anaplotherride, 
the Hippopotamide, and the Suidx” (87, p. 322). Scott says (J. ¢.): “The genus 
[Hlotherium] is so far specialized that it implies a long ancestry, not a member of 
which is, as yet, certainly known, although there are certain Hocene genera, which 
throw some light upon the problem.’”’ Stehlin in his discussion of the dental struc- 
ture of the Entelodontidx (90, pp. 121-123) concludes in a footnote (p. 123) by say- 
ing: “jedenfalls liegt die Vorgeschichte der Elotherien noch sehr im Dunkeln.” 
It is apparent that, although we are well acquainted with the general anatomical fea- 
tures of this family, we can for the present at best only speculate in a'general way 
as to the early history of the group. From the work of Schlosser it is plain that he 
regards the early Tertiary of the Old World as the home of the ancestral line of 
the Hntelodontidx, which may possibly prove to be true, unless “‘ we may suppose,” as 
Matthew has stated in connection with his study of the genus Ancodon,” “ that from 
a diffusion center in Northern Asia early stages in the evolution of [this] phylum 
[also] reached Europe,” and that the American form reached North America at the 
beginning of the Oligocene. 
As for the known forms in the early American Tertiary there is not one which 
can properly be regarded as truly ancestral to the family. Achxnodon of the Bridger, 
and A. wintense of the Uinta are already too far advanced in the modification of 
their dentition, having but three premolars, while the limbs of A. wintense would 
seem to have retained a more primitive condition, having “ four [? functional] digits 
in the pes” (72, p. 105). The suggestive resemblances of the known characters of 
Achxnodon found in the Bridger formation, and A. wintense of the Uinta, should, 
I think, be regarded only as pointing to a remote relationship ; indeed it would seem 
that no great violence is done in referring these general resemblances to parallelism, 
which was no doubt a greater factor in moulding characters than is sometimes real- 
ized. The primitive bunodont teeth, the characteristic glenoid cavity of the skull, 
the expanded zygomatic arches, and the elongated muzzle of these earlier Tertiary 
forms are not to be dismissed so easily, as they are certainly most suggestive of the 
Fintelodontide. But, as has been suggested by others (87, p. 322) there is no more 
® Bull, Am. Muesum of Natural History, Vol. XXVI, p. 4, 1909. 
