the osteology of HY.EN 0 D 0 N. 535 
however, slunv that the "enera inpnOr,n£.ri a. ^ v 
lower molars, thoiigli still hi a very |)viinitive''ti l”"” 1 
the premolars, canines and incisors of both jaws iiiTlie “•'"8''’ “ 
which might easily be modified into those of the other 
present a partienlar resemblance to the H,„od,ntid^ Ztlkt 
skeleton of favors the same view of its relationship to tlic other families 
at libnla” “* with the coWd and the calcanenm with 
So far as is yet known, tile Oxymiids: are an American family, the supposed 
members o it which have been found in France being inferred to it with very doubt- 
ful pi opiu'ty. Hie group tnust have originated in the interval between the Puerco 
and asatdi formations from some Piierco genus not jot identified, but which, in 
all probabditj. was hut little removed from Deltatherium. The Hya-nodontid<s', on 
the other hand, arose in the Old World, appearing first in the upper Eocene (or lower 
Ol.gocene) and hj a later migration reaching North America, where they are not 
known before the (upper) Oligoccne, or White River beds. 
Pterodon apparently did not accompany Hycenodon in this migration, though 
it is represented by tlie very closely allied genus Pemipsalodon, which differs only 
in tiie character of the talon on nis- It is a significant fact that this genus has been 
found only in the Titaiiotlierium-beds of Canada (lat. 49°, 35' N.) which contain a 
fauna in several respects difl'erent from that of the regions farther south and one which 
in many ways is more distinctively allied to the Oligocene fauna of Europe. These 
differences are doubtless owing to climatic and geographical factors rather than to 
any discrepancy of geological age. Assuming, as we may safely do, that Hctni- 
psalodoH came from the Old World, the Cypress Hills region would probably repre- 
sent its sontherninost range. 
Any attempt to comstruct a series of genera leading to Hyeenodon Avould be 
premature, though Proviverra, or some very similar form, will doubtless prove to be 
one of the genera through which the line of descent passed. 
LIST OF PAPERS QUOTED. 
1. Filhot, IT. — .Memoires stir qiielques Maramiferes Fos.«iles. Toulouse, 1884. 
2. Leidy, J. — The E.Ktinct Haninialian Fauna of Dakota and Nebraska. Philadelphia, 1869. 
3. Osborn, H. F. and Wortman, J. X.— Fossil Mammals of the Wahsatch and Wind River Beds 
Bull. American Museum of Natural History, New York, Vol. IV, 1892. 
4. Fo.ssil Mammals of the Lower IMioceue White River Beds. Ibid, Vol. II, 1894. 
5. Schfosser, .V.— Die Atfeii, Leinureu, etc., des europaischen Tertiars. Th.I. Reitriige zur Palseon- 
tologie Oesterreich-Eiigarus, VI Bd. Vienna, 1887. 
6. Scoff, W. R-On some new and little known Creodonts. Jourii. Acad. Nat, Sci. Phila., Vol. IX, 
No. 2, 1887. 
7. A Revision of the North American Creodonta. Proc. Acad. Nat. Sci. Phila., 1892. ^ 
8. iroz-Xmii, .7. L.— Osteology of Patriofelis, a Jliddle Eocene Creodout, Bull. Amer. Mus. Nat. 
Hist., \'ol. VI, 1894. 
9. Ziffdil, K. r.— Haiidhuch der Rahcontologie, I Ahth., IV Bd. Munich A Leipsic, 1890-189.^ 
70 JOUKN. A. N. S. PHILA.. VOL. IX. 
