618 The Phylogeny of the Camelide. [July, 
etsagicus, also from the Wasatch Eocene of the Big Horn river, 
is represented by a portion of a 
robust lower jaw as large as that 
of a fox. 
But one species of Stibarus is 
known, and that from jaw fragments 
only in my museum and in that of 
Princeton College. These fragments 
appear to have belonged to an animal 
of the size of a pine weasel or martin, 
but the premolar teeth are very 
large for the size of the jaw and 
may indicate a larger animal. The 
anterior ones, ? first and second, 
have two roots each, and are quite 
elongate in the fore and aft direc- 
tion. They are separated by a very 
narrow diastema from the tooth in 
front of them, ?the canine. The 
premolars are compressed and have 
a straight median cutting edge. 
Ss This edge is thrown into two lobes 
PE cage Si Eeri between the anterior and ` posterior 
Cone a ogg h Eo- basal ones, the anterior only being — 
of W Fig. 2 Saperi Bes 
molar teeth from ‘below; b; mandible, the larger. The whole tooth rese 
left side ; c, do, fi 3 
ee aa aCe nom ater SP „blesa rather low premolar Idh 
a. d, — behind; e, from g dog, and was evidently quite 
outside; /, from- insid O 
from PAS U. S- Ge l. a effective as a cutter of soft sub- 
Ters., Vol. ii, E. V. Hayden, stances. 
Of the Poébrotheriidz there are two genera. These differ 5 
follows : 
_. First premolar of upper jaw elongate and with two roots....+ Potbrotherium pai 
mint upper premolar short and with a simple conic root...-- Gomphothertum T 
In Poëbrotherium we have two species, a larger P. l - nals 
Cope, and a smaller Z, vilsoni Leidy (Fig. 9). Both are pren 
of graceful and slender proportions, of about the size "i ase 
a yi 
a of the existing gazelles. Their heads were, however, © 
. narrowed form towards the end of the muzzle. The ag ii 
these animals have been found in the White River beds 
