10 Bulletin American Museum of Natural History. [Vol. XXXIV, 
Skull. Owing to the poor preservation no sutures can be safely dis- 
tinguished. The general proportions of the skull are much as in Vulpavus. 
The frontal region appears to be wider than in that genus, the front of muzzle 
broader. The sagittal crest is of moderate height, the occiput appears to 
be broad and low, and the brain-case is fairly capacious, comparing with 
Vassacyon, smaller relatively than in Vulpavus but much larger than in 
Ss & REN SEG. si A.M. 
(a 1 
Fig. 7. Thryptacodon olsent, skull, top and side views natural size, and crown view of 
upper teeth, four-thirds nature. Type specimen, Gray Bull beds, Big Horn Basin, Wyoming. 
Arctocyon and materially larger than in Didymictis. The basicranial region 
appears to be shorter than in Didymictis and Vulpavus; the bulla is absent 
as usual, the auditory prominence large and prominent (? owing to crushing). 
In other respects it accords with Vassacyon so far as comparisons can be 
made. 
