1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 69 
roots connate. The heels of the molars are also like those of Thinocyon, 
compressed, narrow and bordered by two subequal crests. In most species 
of Sinopa the heels are relatively broader and usually larger; but I can find 
no constant generic distinctions in the construction of the molars. 
Upper and lower teeth of the same individual are preserved in Nos. 15240 
and 15246, and No. 15171, a crushed and imperfect skull, shows the upper 
teeth and a few cranial characters of interest. The remainder of the speci- 
es 
/ 
, w\ 
‘ cw ) ; 
No. HELET 
\ : Mm 
/ / Sy is 
/ =m 
base ee ae : 5 
Fig. 59. Fig. 60. 
Fig. 59. Prolimnocyon atavus, calcaneum of type specimen, natural size, dorsal view. 
Fig. 60. Prolimnocyon atavus, upper teeth, from skull No. 15171, crown view, enlarged 
to two diameters and natural size. The outline of p‘ is taken from No. 15246. Gray Bull 
beds, Big Horn Basin. 
mens are all lower jaws, fragments of the skeleton being associated with the 
type only. 
In the skull, m? is transverse, nearly as wide as m', the metacone vestigial, 
parastyle long and curved. Mis represented by two alveoli which indicate 
a tooth one-half or one-third the transverse width of m®. M1’ is much like 
the corresponding tooth in Sinopa, but with me and pa more closely connate. 
F* is 3-rooted triangular, smaller than m'; p* has also a small internal root. 
The skull is too poorly preserved to show many important data; the in- 
terorbital width is large, as in Limnocyonine, without the frontal fossa 
characteristic of Hyeenodonts; the occi- 
put is broad, and the general propor- 
tions agree fairly well with Thinocyon. 
The sacrum is narrow, although 
wider than in Thinocyon; the sacral ribs 
are much narrower than in Sznopa or 
Fig. 61. Prolimnocyon atavus, lower 
£ ritemnodon. The anterior ay gapophy . jaw, outer view, natural size. No. 15169; 
ses on the first sacral vertebra are nearly outlines of ps and m2_s restored from Nos. 
We WW? ss 15246, 16816. Gray Bull beds, Elk 
flat; in Thinocyon they are considerably Bone RIE Hoss tow, sone. 
more concave, in 7'ritemnodon they are 
about semi-cylindrical. The head of the tibia shows a low enemial crest. The 
caleaneum has a rather short tuber, a small fibular facet, moderate peroneal 
process, cuboid facet nearly as wide as it is deep, and moderately oblique. 
No. 15169 
Ay M4. 
