PETERSON : DESCRIPTION OF NEW RODENTS NAG 
STENEOFIBER COMPLEXUS Douglas. 
(Pr. Amer. Philos. Soc., Vol. XX., 1901, p. 249; Bull. Amer. Mus., Vol. XVI., 
1902, p. 304.) 
The type was found in the Lower Madison Valley, about nine or ten miles south 
of Three Forks, Montana, in the Oligocene formation ; horizon not clearly defined. 
The type is before me, and consists of a part of a skull and the lower jaws of a 
young individual. The temporal ridges apparently extended well backward before 
they united ; the muzzle is small and of considerable length. There is a long and 
gently curved diastema between the cheek teeth and the incisors; the latter are covered 
with heavy enamel anteriorly, and have a rounded face. ‘‘ The masseteric area does 
not extend so far forward as in S. hesperus, and the anterior margin of the coronoid 
process rises opposite the back part of mg, and is nearer tothe molar. This process 
has an entirely different form in this species. It is high; the anterior border is 
straight and rises steeply. The angle is inflected inward and is rounded, not angu- 
late anteriorly and posteriorly, as in S. viciacensis.” 
The anterior face of the lower incisor is not so convex as in S. hesperus, the 
posterior angle is broadly rounded. ‘The outer part of the cutting edge is rounded, 
not angulate. 
The upper cheek teeth are very complex, which is due to the small degree of 
attrition, the animal being young and retaining the milk premolars. Matthew 
regards most of the distinguishing characters given by Douglass as subject ‘to 
change: with age and unsafe specific distinctions. The separate temporal crests 
may constitute a valid specific distinction.” The vertical position of the ascending 
ramus of the mandible seems to suggest S. pansus as described by Matthew and 
Gidley, and is probably a valid character. When better material is found it may 
become necessary to unite S. complexus with S. hesperus. 
STENEOFIBER Fossor Peterson. 
From the Upper Miocene, Harrison (Demonelix) beds, in Converse Co., 
Wyoming. 
This species has rather small teeth in comparison with the skull; muzzle and 
nasals moderately long; zygomatic arches greatly expanded; and there is a post- 
orbital angle on the jugal. Tympanic bulla inflated and flask-like, with a long, 
constricted tube, and a large external opening. Basioccipital not excavated, but 
slightly keeled. Palate extending well back of the third true molar. The palatine 
portion of the premaxillaries is greatly arched above the cheek teeth. Upper and 
lower incisors very strong with a flat anterior surface. 
