NOTES ON THE CANID® OF THE WHITE RIVER OLIGOCENE. AQ9 
On the assumption that the dogs and cats are thus quite closely connected, what can 
be said concerning the relations of the other fissipede families with these groups and with 
one another? Of the derivation of the Procyonide nothing is yet known; the family 
may be traced back into the Loup Fork without finding essential changes, but beyond 
that period we lose track of it altogether. The position of the bears and hyenas is rea- 
sonably clear, the latter being late derivatives of the viverrines and the former of the 
dogs, neither family making its appearance until long after the other fissipede groups 
had become clearly differentiated. The Viverride have a great many characters in com- 
mon with both the early dogs and the early Machairodonts ; almost all the structural 
features which are found in both Daphenus and Dinictis recur also in the viverrines, 
and the latter again have many points of similarity to Cynodictis, as has often been 
remarked. That the viverrine features of Cynodictis are more numerous and apparent 
than those of Daphenus is largely due to the small size of the former, which agrees 
much better with the stature usual in the recent viverrines. The viverrines thus seem 
to be derivatives of the same Eocene stock as that which gave rise to both the dogs and 
the cats, though, perhaps, they are more nearly allied to the latter than to the former, 
and apparently they have departed less from that primeyal fissipede stem than has either 
of the other families. Aside from the peculiar character of the auditory bulla and the 
reduced number of the molar teeth, such a genus as Viverra would seem to differ but 
little from the hypothetical Eocene ancestor of all the fissipede families. The Justelide 
represent a quite specialized branch of the fissipedes, but between its earlier and more 
primitive members and the corresponding representatives of the viverrines are so many 
structural resemblances that Schlosser does not hesitate to derive them from a common 
stem. An interesting and significant example of this community of characters among 
the early representatives of the different fissipede families is given by the os penis of 
Cynodictis, which resembles that of the mustelines much more closely than that of the 
modern dogs. This probably indicates that all of the earlier fissipedes had this bone 
shaped very much as in the existing mustelines, which have thus retained the primitive 
form, while in the other families it has become much modified in shape and size. This 
would explain the apparent anomaly of the very large os penis of Cryptoprocta which is 
so different from that of the other viverrines. According to this way of looking at the 
subject, there was a middle Eocene group of flesh-eaters, perhaps the creodont family 
Miacide, which rapidly diverged into four principal branches, the cats, dogs, viverrines 
and mustelines, all of which families were established in the late Eocene or early Oligo- 
cene, and to these should perhaps be added a fifth family, the Procyonide, though of this 
we know nothing definite. The Fissipedia are thus probably a monophyletic rather 
than a polyphyletic group, which was derived from a single creodont family. 
