614 = -` The Phylogeny of the Camilide. 
instead of four crescents, these teeth should possess four cones or 
tubercles perhaps more or less flattened. Such forms are already 
nown as ancestral to some other. Ruminantia, 
as for instance the genus Anthracotherium, 
where the external cones are flattened on the 
outer side, or Dichobune; where the cones are 
not flattened’at all. In both of these genera : 
there are five tubercles to the superior molars, 
and the lateral (11, v) digits are present. We 
possess some fragments, however, of a lost 
genus from the age of the Poëbrotherium 
(the White River Miocene, or Oligocene), 
which very probably represents the one which 
fills the interval. This has been named Stib- 
arus (Cope), and it is only known from parts 
of lower jaws which contain premolar teeth. 
These have a great resemblance to thẹ corre- 
i Gia sponding parts of an older genus of the same 
tise capes and end of line, -Pantolestes, from the Wasatch forma- 
wn eitoni Let tion or Lower Eocene. It might be suspected 
_ Original. that, Stibarus is a member of the Panto- 
lestidze but for one fact., The superior molars of Pantolestes be- 
long to the primitive type which has only three tubercles or 
cusps. No genus of ungulate mammals having this character is 
known to pass the bounds of the Eocene series of epochs in any 
country, and it is extremely improbable that Stibarus will prove 
to be an exception to this rule. I have very little doubt that the 
superior molars will be found to be quadritubercular, but it is : 
impossible to be certain whether the tubercles are simple oF cres- 
_centic. The resemblance of the premolars to those of Pantoles- 
tes leaves the probabilities in favor of their being simple. In 
_ case Stibarus represents a family in the wide interval between “Ta 
oe Pantolestide and the Poébrotheriide. 
Messrs. Scott and Osborn have described a dias ton 
Bridger Eocene of Wyoming, as a probable member of n pa 
known from two premaxillary and a part of one maxi 
The former are slender and bear a complete set of incisor ‘his 
which are followed by a large canine. It is probable that 
genus oome in the camel sèries, but it cannot yet be eo 
