MYOMOEPHA. 849 



EuMYs ELEGANS Leidy. 



Proceedings Academy, Philada., 1856, p. 90; loc. cit. 1857, p. 89. Extinct Mammalia of Dakota and 

 Nebraska, p. 342, PI. XXVI; figs. 12, 13, 1869. Cope Ann. Report U. S. Geol. Snrv. Terrs., 1873 

 (1874), p. 474. 



Plate LXV; figs. 1-14. 



I found remains of this rat exceedingly abundant in the shallow washes 

 of the White River rocks in Eastern Colorado. It had previously been 

 known from a single imperfect jaw-fragment from Dakota, found by Dr. 

 Hayden. 



The sutures of the cranium anterior to the brain-case are distinct, in- 

 cluding those that separate the frontal and nasal bones on the median 

 line. The suture separating the maxillary and premaxillary bones crosses 

 the palate a little behind the line connecting the bases of the zygomata, 

 passes upwards a little in front of the latter and then turns posteriorly, 

 joining the nasal suture at its posterior extremity. The apices of the pre- 

 maxillary and nasal bones fonn an acute angle above the middle of the 

 orbit, and the frontals enter an acute notch between them. The palato- 

 maxillary suture crosses the palate opposite the middle of the second molar 

 tooth. 



The nasal bones are strongly convex at the extremity, and extend a. 

 short distance beyond the base of the superior incisor teeth. They narrow 

 posteriorly, become plane, and then concave on the median line. The 

 carina of the frontals incloses a median groove. The superior portion of 

 the maxillary bone presents a subround fossa at the entrance of the fora- 

 men infraorhitale. The latter is overarched by a slender bridge, which is as 

 wide as thick. The malar bone does not appear in the base of the zygoma, 

 whose inferior expansion presents a shallow, wide fossa, downwards and 

 forwards. The anterior border of the base is free, inclosing a fissure which 

 descends from the superior portion of the foramen. The posterior margin 

 of the base is opposite to the anterior part of the first molar tooth, a point 

 which is nearly attained by the incisive foramina. The latter are separated 

 by a narrow septum on the median line. The free border of the palate 

 is slightly concave, but does not advance beyond the posterior part of the 

 third superior molar. The palatine foramen is large, and is opposite the 

 posterior half of the second molar. 

 54 c 



