40) Bulletin American Museum of Natural History... [Vol. XXXIV, 
pavus, but has some peculiarities of its own. The principal characters of 
the skull and skeleton are known from specimens secured by Mr. Granger 
in the Big Horn Basin, and may be compared with Vulpavus and Miacis 
as described by Matthew in 1909. 
The skull is proportioned as in Vulpavus, very much shorter than in the 
Viverravine, the basicranial region broad and long, the glenoid articulations 
set well forward of the occipital condyles. The detailed construction of 
this region is obscured by matrix but appears to be much as in Vulpavus. 
Occiput broad and low; sagittal crest moderately developed. Nasals 
somewhat broader posteriorly than in Vulpavus; premaxillee more reduced. 
Facial exposure of lachrymal as in Miacis and Vulpavus. 
Upper molars with short extension of parastyle, well developed hypo- 
Fig. 34. Vassacyon promicrodon, skull, natural size. No. 15163, lower Gray Bull beds, 
Big Horn Basin. 
cone, paracone somewhat larger than metacone; m! considerably larger than 
m”; m*® two-rooted. P4 carnassiform. Anterior premolars reduced; p? and 
p* two rooted with small or rudimentary heelcusps; p! one-rooted. In the 
lower jaw m, is carnassiform with large basin heel; ms tubercular, large, 
with low trenchant heel; m3 small, one-rooted, oval, tubercular cusps 
obscured. Premolars reduced, spaced; canine large, flattened, jaw below it 
angulate. 
Skeleton much as in Vulpavus. Scaphoid, lunar and centrale united to 
a single bone. Trapezium larger than in any later Miacide. Claws com- 
pressed, high and sharp, not fissured at the tip. 
