PETERSON : DESCRIPTION OF NEW RODENTS 175 
of South Dakota. This may or may not be this species. It is distinctly separated 
from S. fossor by the moderately excavated basioccipital without the median ridge, 
and by the shorter palate, which “is roofed over as far back as the anterior border 
of the third true molar.” In 8. fossor the posterior narial opening is 4 mm. back of 
the third true molar. 
The ascending ramus of the mandible in the American Museum specimen is 
more vertical, and relatively higher than either in S. peninsulatus, 8. fossor or S. 
barbourt. The specimen indicates an animal intermediate in size between S. fossor 
and S. barbouri. 
STENEOFIBER MON'TTANUS Scott. 
(Trans. Amer. Philos. Soc., Vol. XVII., 1893, pp. 76-78; Bull. Amer. Mus., 
Vol. XXI., 1902, pp. 303-304.) 
Professor Scott writes me that the type of this species is lost. It was found in 
the Upper John Day beds of Smith River (Deep River), Montana. 
“The incisors are narrow, with anterior faces which are less convex than in 
Castor and are covered with a thick layer of orange-colored enamel.” ‘The caudal 
vertebree indicate that this species had a longer and more slender tail than the 
beaver; the anterior portion was provided with chevron bones.” 
“The humerus has a rather slender, trihedral shaft and prominent deltoid 
ridge, which terminates in a massive, overhanging hook ; this hook is proportion- 
ately even better developed than in Castor. ‘The supinator ridge is also conspicuous 
and continues high up upon the posterior aspect of the shaft. . . . The internal 
epicondyle is very prominent, massive, and rugose, and is perforated by a large 
foramen.” 
“The femoral trochanters are well developed, but the third is placed more prox- 
imally than in S. peninsulatus or in the beaver.” In 8S. fossor the third trochanter 
is like that of S. peninsulatus. ‘The caleaneum has a short, depressed, irregular, 
and club-shaped tuber; the sustentaculum is notably smaller than in the modern 
species, and the external projection near the distal end much more prominent; the 
The third metatarsal 
”) 
cuboidal surface is of triangular outline and slightly concave 
is relatively very much more slender and shorter than in Castor and of different 
shape, as the shaft is of nearly uniform size throughout, not being contracted in the 
middle nor expanded distally ; it is also more depressed and flattened, and the head 
for the first phalanx less enlarged. ‘The proximal end has an oblique surface for the 
ectocuneiform, which is abruptly constricted behind and continued as a narrow pos- 
terior tongue.” 
The upper and lower teeth of the type are figured in the Bull. Amer. Mus., Vol. 
