176 MEMOIRS OF THE CARNEGIE MUSEUM 
XVL, 1902, p. 303. Matthew states that the type is “allied to S. nebrascensis, but 
larger, with somewhat longer teeth, and enamel inflections deeper and more complex. 
The type is an old individual, whence the antero-posterior direction of the internal 
upper and external lower enamel inflections on which Professor Scott largely relies 
to distinguish the species.” The proximal position of the third trochanter on the 
femur, referred to above, may be considered as of specific value. 
STENEOFIBER HESPERUS Douglas. 
(Pr. Amer. Philos. Soc., Vol. XX., 1901, pp. 247-248; Bull. Amer. Mus., Vol. 
XVI, 1902, p. 304). 
The type was found on Black Tail Deer Creek, about thirty miles above Dillon, 
in Beayerhead Co., Montana, in the Oligocene formation ; the horizon not clearly 
determined by characteristic fossils. 
The mandible is somewhat smaller than that of S. pansus of the Loup Fork of 
New Mexico. “The animal was not so robust as the New Mexico species.” ‘The 
masseteric¢ area does not extend so far forward. “The anterior surface of the incisors 
is more convex than in the beaver, Castor canadensis, and the antero-posterior 
diameter is proportionally greater.” 
? 
“The two anterior [lower] molars (m1 and m2) are broader and longer” than 
those in S. pansus. “The outer enamel inflections do not extend so far down on 
the outside of the teeth, are more open and incline more forward, and the outer lobes 
more angulate.” 
The type of this species is illustrated in Matthew’s paper referred to above. In 
speaking of this specimen Matthew regards it as “close to S. montanus, if not iden- 
tical ; the difference in age prevents any accurate comparison. ‘The size is the same 
at similar points of wear; the upper [should read lower: there are no upper teeth 
in the type] incisors are more rounded externally, but the value of this character is 
doubtful.” The flat anterior face of the incisors in S. fossor is constant throughout 
the entire series of skulls and lower jaws in the Carnegie Museum collections, and is 
considered as of specific value. 
The inferior premolars are the only basis for comparison in S. montanus and hes- 
perus. The internal enamel folds are quite distinet on all the cheek teeth and the 
configuration of the triturating surface of pz in S. hesperus is certainly more complex 
than in S. montanus. This is due in part to the younger age of S. hesperus. I give 
below the measurements of pz taken from the author’s descriptions : 
Sleneofiber montanus. Wength of lower molar (py)...cccecceee ceseececees cress cceess ena sersecsseceaeeseeenes 0.005 m. 
Width of lower molar (p;)........... Q696 606 d9accadas00Ne6;809000000000 canbo0s0D5000 0.004 “ 
Steneofiber hesperus. Length of pz at base..........0... ccceceseeccsceececeeeceneecseceneceeteeerereeteseeee ates 0.005 ‘* 
WGN OH SO Bib EES 6 cecotecoatadbod "20000000 cdanba600 509000000 atioogosoecaobeps0005000000000 0.0045 ‘* 
