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Second Contribution to a Knowledge of the Miocene Fauna of Oregon. 

 By E. D. Cope. 



{Bead before the American Philosophical Society, December 5, 1S79.) 



Two contributions to the present subject have been heretofore made by 

 the writer, viz., in the Proceedings of the American Philosophical Society, 

 for November, 1878 ; and in the Bulletin of the U. 8. Geological Survey of 

 the Territories for February, 1879. In the latter article thirty-eight species 

 of vertebrata were enumerated as having been discovered in the Truckee 

 beds of the White River formation of Oregon, of which all but one were 

 mammalia. 



I have since conducted explorations in that region, the expeditions being 

 mostly under the direction of Jacob L. Wortman. This gentleman has 

 obtained a great many specimens, several of which indicate new species, 

 which it is the object of the present article to describe. In addition to these 

 discoveries, Mr. Wortman has sent remains of Lacertilia and OpJiidia, or- 

 ders previously unknown in Oregon. I had discovered them in the White 

 River formation in Colorado in 1873. 



HESPEKOMYS NEJ1ATODON, Sp. UOV. 



This rat is represented by a beautiful skull, discovered by Prof. Thomas 

 Condon, of Eugene city, and by several jaws, and other fragments subse- 

 quently found by Mr. Wortman. 



The frontal region is not contracted as in Eumys elegans and Fiber 

 sibethicus, but the superciliary ridges are well separated from each other, 

 as in Hesperomys americanus. The frontal and posterior nasal regions are 

 slightly concave in transverse section. The molars display tubercles on 

 one side, and crescents on the other, the former being external in the su- 

 perior series. The first superior molar has an additional tubercle at its an- 

 terior extremity. The incisors have a transverse anterior face, which is 

 divided by several delicate ridges. 



Length of superior molar series, .0065 ; length of first superior molar, 

 .0028 ; interorbital width, .0042. Length of inferior molar series (speci- 

 men No. 2), .0064; length of first molar, .002; width of incisor, .001 ; 

 depth of ramus at second molar, .004. 



SCIURUS VORTMANI, sp. 110V. 



Like the S. relictus, of the Colorado White River beds, this is a rare 

 species, being only represented by a mandibular ramus in my collection. 

 This part is remarkable for its depth as compared with its length ; and the 

 base of the coronoid process has an anterior position. It rises opposite the 

 posterior part of the third molar, and its anterior border descends to a point 

 just below the posterior part of the first molar. The inferior border of the 

 masseteric fossa is a prominent edge, which descends below the inner in- 

 ferior margin of the ramus. The molars diminish regularly in size for- 

 wards ; their crowns are basin-shaped, with the anterior angle of the ex- 



