DAKOTA AND NEBRASKA. 339 



formation of Saint-Gerand-le-Puy, France, represented in plate 48 of Gervais' Pale- 

 ontologie Francaise. Tlie teeth also of the Nebraska specimens bear a near resem- 

 blance to those of the animal just named. 



From these resemblances the Nebraska fossils were referred to a species of Steneo- 

 fiher, about two-thirds the size of S. viciacensis. Sleneofiher has been viewed by Dr. 

 Bronn, in the LethiBa Geognostica, as synonymous witli Chalicomys, of which the 

 type is C. Jdgeri, indicated by the portion of a lower jaw and teeth, from the miocene 

 formation of Germany. The lower jaw of Steneofiber viciacensis remains unknown ; 

 if, however, it should prove to possess a form such as that of Chalicomys Jdgeri, as 

 represented in figure 19, plate xxv, of Kaup's Ossemens Fossiles, it would appear to 

 be different from that in the Nebraska rodent under examination. In the lower jaw 

 of the latter, the base pursues the course of that in the Beaver, but in Chalicomys 

 Jdgeri it possesses a comparatively strong, downward convexity. Under the circum- 

 stances, I have preferred placing the Nebraska fossils under consideration in a new 

 genus, distinguished by tlie name heading the pi'esent chapter. 



In the mutilated skull, small fragments of the cranium held in position by the in- 

 cluded mass of matrix exhibit the following details in comparison with the figures of 

 the skull of Steneofiber viciacensis, represented in Gervais' Paleontologie Francaise, 

 plate 48. 



The forehead presents the same triangular form and proportionate size. The tem- 

 poral fossae appear to have had the same form and proportionate capacity. Tliey 

 were separated in the same manner by a long sagittal crest, extending forward upon 

 the frontal bone. The cranium, just back of the forehead, was equally constricted. 

 The external auditory passage formed a short oblique canal, with its orifice directed 

 outward and backward in the same manner. The palatal region likewise had the 

 same form and construction, and the infra-orbital foramina held the same relation of 

 size and position as in Steneofiber viciacensis. 



The incisors in both jaws are proportionately as long and strong as iu the Beaver, 

 and they have the same form. 



The lower jaw, figures 8, 9, is strong, and approaches in form that of the Beaver. 

 The fore part from the ascending ramus closely resembles the corresponding portion 

 in the latter. The base also pursues the same course. Tn the lower jaw of Chalico- 

 mys Jdgeri, as previously stated, the base forms a comparatively deep convexity, in 

 advance of the position of the angle. The latter, in the Nebraska fossil, is of less 

 proportionate breadth than in the Beaver, and is much bent inwardly. The condyle 

 is relatively higher or at a proportionately longer distance from the base. It forms a 

 eingle superior convexity as in the Muskrat, but proportionately less wide antero-pos- 

 teriorly, and it does not extend downward externally as in the Beaver. The poste- 

 rior border of the jaw, a little below the condyle, forms a 3-like double curvature, as 



