2, MEMOIRS OF THE CARNEGIE MUSEUM 
PRINCIPAL CHARACTERS OF THE NORTH AMERICAN SPECIES OF 
STEN EOFIBER. 
STENEOFIBER NEBRASCENSIS Leidy. 
Pr. Ac. Nat. Sci. Philad., VIII., 1856, p. 88. 
This species was found in the Bad Lands of White River, §. Dakota, in beds C 
and D of Dr. Hayden and Leidy’s section. (The Extinct Mammalian Fauna of 
Dakota and Nebraska.) This horizon is perhaps equivalent to the Protoceras beds.' 
(See Matthew, Classification of the Freshwater Tertiary of the West.— Bull. Am. 
Mus. Nat. Hist., XI!., 1899, pp. 19-75.) 
This species is distinguishable by a small tympanic bulla, with the “ external 
auditory passage forming a short oblique canal with its orifice directed outward and 
backward in the same manner” as in S. viciacensis. The angle of the lower jaw “is 
of less proportionate breadth than in the Beaver and is much bent inwardly. ‘The 
condyle is higher or at a proportionately longer distance from the base. The single 
superior convexity ”’ does not extend downward externally as in the Beaver (p. 339, 
Ext. Mamm. Faun.). Dr. Matthew (Bull. Am. Mus. Nat. Hist., XVI., 1902, p. 
301-802) refers certain material in the American Museum collections from the 
Protoceras beds to Leidy’s species, and further characterizes it as follows: ‘“ Long 
and narrow muzzle, small bulle, sharp sagittal crest, and small braincase. The 
postorbital constriction is moderate, the pattern of the teeth rather complicated, two 
deep fossettes anterior to the external inflection on p* remaining in the well worn 
teeth of No. 1428.” (This is the catalogue number of the specimen referred to 
S. nebrascensis. ) 
STENEOFIBER PENINSULATUS Cope. 
Bull. U. 5. Geol. Surv. Terr., VI., 1881, p. 370-373, and Tertiary Vertebrata, 
1884, p. 840. 
From the John Day formation (? Diceratherium beds), Oregon. 
In the Revision of the Mylagaulids, Beavers, and Hares of the American Terti- 
ary (Bull. Am. Mus. Nat. Hist., XVI, 1902, p. 291-310), Matthew defined this 
species as ‘“‘ more robust than the last [S. nebrascensis], distinguishable by the large 
bullze and probably by the: broader muzzle, wide occiput, larger brain-case and 
wider sagittal crest. The postorbital constriction is very narrow in the type, but not 
in the second specimen.” (The latter character may indicate individual variation.) 
The configuration of the cheek teeth in Steneofiber varies so much with age, that 
'Wortman, Bull. Am. Mus. Nut. Hist., V., 1893, pp. 101-102. 
