No. 5. — Preliminary Account of the Fossil Mammals from the 

 White River Formation contained in the Museum- of Comparative 

 Zoology. By W. B. Scott and Henry F. Osborn. 



This paper is a brief abstract of a memoir upon the Cambridge col- 

 lection of Miocene Mammals, which is now in preparation. This 

 collection was made by Mr. Samuel Garman in Nebraska and Dakota, 

 and has been very kindly placed in our hands by Professor Agassiz for 

 preparation and description. The work of excavating, cleaning, and 

 mounting the fossils has been for the most part performed jy Dr. 

 Franklin C. Hill, Curator of the Geological Museum at Princeton, and 

 to him our best thanks are due. The drawings were all executed by Mr. 

 R. Weber. 



Geological Museum, Princeton, N. J., July 9, 1887. 



RODENTIA. 



Palaeolagus Haydeni, Leidy. Several specimens of jaws and teeth repre- 

 sent this species in the collection, but add nothing to our previous knowledge. 

 Ischyromys typus, Leidy. Isolated teeth. 



OREODONTA. 



Hyaenodon horridus, Leidy. A most valuable and indeed unique speci- 

 men of this species, belonging to the Cambridge collection, has already been 

 described by one of us elsewhere.* Here it will suffice to recapitulate some of 

 the more important facts established by it. The posterior dorsal and lumbar 

 vertebrae show the characteristically creodont feature of involuted zygapophy- 

 ses, such as are not found in any known carnivore. The scaphoid and lunar 

 bones are separate, and a distinct central is found; the manus is plantigrade 

 and pentadactjd, and the ungual phalanges are deeply cleft. This specimen 

 renders it perfectly certain that Hyctnodon was a typical creodont, and that it 

 was in all probability an aquatic form. It also shows that Hycenodon is not at 

 all allied to Mesonyx, as has been supposed, but rather to Pterodon, Protopsalis, 

 and Oxycena. 



* Scott, Jouin. Acad. Nat. Sci, Phil., Ser. 2, Vol. IX. No. 2. 



VOL. XIII. — NO. 5. 



