472 Bulletin American Museum of Natural History. [Vol. XXXIV, 
This species agrees with Cynodontomys in the inequality of the two outer 
cusps of p*, the lack of trittoconid and inequality of pr® and de® on ps, which 
appear to be the best distinctive characters of Cynodontomys. It is there- 
fore transferred to that genus. 
Some twenty jaws or parts of jaws from the Lost Cabin horizon of the 
Wind River basin agree with the type in all essentials. No. 14969, a well 
preserved right and left ramus represents the species in the collection from 
Beaver Divide, south of Lander, Wyo., the teeth complete except for the tip 
of the incisor. One ramus is abnormal! in the lack of ps. 
The enlarged front tooth has a pointed subspatulate crown, wedge- 
shaped in cross section with nearly flat inner surface, moderately convex 
=< Ja 
S 
ee) i ( 
\ yw a ey 
No. (4703 
A. 4. 
SS. 
we 
aN = 
“ WK i 1G ge 
; | 
Sy We As Mi Je , 
Fig. 42. Cynodontomys scottianus, upper jaw, outer and crown views. Lost Cabin beds, 
Wind River basin, Wyoming. 
outer surface, sharp posterior and thick rounded anterior border, It is 
not so long as in Mixodectes, more flattened. The tooth behind it is de- 
termined by Osborn as a canine, but appears to be more probably a premolar 
(pz). It has a simple pointed crown and two connate roots. The third 
premolar has two well separated roots and a simple pointed trenchant crown 
with small heel. Ps is submolariform, with strong inner cusp nearly as high 
as the protoconid, broad bicuspid heel. 
The fourth upper premolar has two strong external cusps, the posterior 
one a little lower than the anterior, distinct conules and parastyle, and the 
inner half of the tooth is broadened out so as to give it a subquadrate form 
like the molars. Mesostyle absent on p‘, rudimentary on mi, 
