140 MEMOIRS OF THE CARNEGIE MUSEUM 
in reading and correcting the manuscript and making kindly criticisms, of Mr. 
Sydney Prentice for making the drawings, of Mr. O. E. Jennings for working out 
the details in microscopic sections made from Demonelix and furnishing notes on his 
observations, of Mr. A. 8S. Coggeshall for photographs and of Mr. A. W. Vankirk for 
making the microscopic slides and assisting in cleaning up the material. To Direc- 
tor W. J. Holland is due special acknowledgment for the privilege of describing 
this interesting and complete material. 
Steneofiber fossor spec. nov. 
This species is quite common in the Harrison (Demonelix) beds in eastern Wy- 
oming and western Nebraska. This horizon immediately overlies the Monroe 
Creek beds and is probably equivalent to the upper John Day. There are fourteen 
specimens of this species in the Carnegie Museum collections, which were found 
inside of as many Demonelices. In some cases nearly complete skeletons were 
discovered. The type (No. 1217) was found near the rounded end of a “rhizome,” 
and consists of the cranium, the vertebral column, including eleven caudals, (the 
extreme tip of the tail is missing), both clavicles, and a fairly complete set of ribs. 
The right and left fore limbs are complete, except the superior part of the right 
scapula and the feet. The pelvis and the posterior limbs are present, including the 
greater part of the right pes. No. 1208 is used as a cotype, and has the skull, lower 
jaws, eleven presacral vertebrae, the sacrum, both clavicles, the manubrium, and 
several ribs. ‘The fore limbs are fairly well represented, and there are some frag- 
ments of the hind limbs. In the following description of the osteology of S. fossor 
use will be made of supplementary material, when, by so doing, additional light is 
thrown on the subject. In each instance the museum catalogue numbers will be 
referred to in connection with the specimens. 
THE Supertor Dentirion. 
The superior incisors are comparatively as large and strong as those of the recent 
beaver; anteriorly the broad and flat surface is covered with a heavy coating of 
enamel, which forms rather sharp angular edges laterally. The rounded lateral and 
posterior faces have no enamel. The antero-posterior diameter is as great as the 
transverse. The chisel-shaped gnawing portions of the teeth are long and terminate 
anteriorly in a broad sharp edge. 
The superior grinding teeth are rather small in comparison with the size of the 
skull. They gradually decrease in size from p* to m?. Their position is nearly 
parallel with the long axis of the skull, and they are placed about midway between 
the anterior and posterior extremities of the skull. 
