BOD. Bulletin American Museum of Natural History. [Vol. XXXIV, 
and similar size and proportions, to Hemzacodon rather than to Microsyops 
is that as with Hemiacodon they are strictly limited to the Upper Bridger. 
Smaller bones of similar type occur rarely in the Lower Bridger and are 
appropriate in size to the nearly related genus Omomys. None have been 
found in the Wind River or Wasatch formations. Muicrosyops on the other 
hand is more abundant in the Lower than in the Upper Bridger and the 
species only slightly smaller, while the closely related Cynodontomys is 
aye 
PN 
i. 7h 
Ny i i cy 
a ‘ Xi Vip AD 
\[o 
ING. Se OFS 
Tay ie 
Soe Be Dua vee Ee 
— —_——_— 
Fig. 24. Hemiacodon gracilis, lower jaw, inner, outer and crown views. Upper Bridger 
beds (Middle Eocene), Bridger basin, Wyoming. Front teeth restored from No. 12037. 
fairly common in the Wind River basin and occurs also in the Bighorn basin, 
but no skeleton material of the type here under discussion has been found 
in these basins. This is by no means conclusive but in default of better 
evidence it may serve as a reason for referring this type of skeleton to 
Hemracodon rather than to Microsyops. Wortman has referred an unassoci- 
ated calcaneum of this type to Microsyops, stating that “there is no other 
known primate in the Bridger to which as regards size it could pertain.” ! 
But the size is more appropriate to Hemiacodon. 
1 Wortman, 1903, Amer. Journ. Sci., Vol. XVI, p. 209, fig. 115. 
