Y. MERYCOCHCERUS AND A NEW GENUS OF MERY- 



COIDODONTS, WITH SOME NOTES ON OTHER 



AGRIOCHCERID^E. 



By Earl Douglass. 

 (Plate XXI.) 



Outline of Contents. 

 (I.) History of .the generic name Merycochcerus. 

 ( II. ) Bearing of our knowledge of the later Tertiary formations of the west upon the 



probable age of the genera Merycochcerus and Pronomotherium . 

 (III. ) Pronomotherium (gen. nov. ) described and compared with the types of Mery- 

 cochcerus proprius and Merycochcerus rusticus. 

 (IV.) Affinities of Pronomotherium. 

 (V.) Relationships of the Flint Creek and other upper Miocene beds. 



I. A History of the Generic Name Merycochcerus. 



In the year 1857 Dr. F. V. Hayden, while on an exploring ex- 

 pedition, discovered opposite Fort Laramie in a stratum of " dull red- 

 dish brown indurated grit" (bed "D" of Hayden's section of the 

 Miocene formations), portions of skulls and mandibles of a new genus 

 of Merycoidodonts. In 1858 these were described by Joseph Leidy 

 under the name of Me jycochoer us proprius. 1 The genus was based on 

 several portions of the upper and lower jaws. 



Previous to this time only four species of Merycoidodonts (Oreodonts 

 auctorum) had been described, Merycoidodon culbertsoni Leidy, in 

 1848, Eucrotaphus jacksoni Leidy, in 1850, Oreodon gracilis Leidy, in 

 185 1, and Oreodon major Leidy, in 1854. These, with the exception 

 of Eucrotaphns jacksoni, were represented, so far as the skulls and 

 dentition are concerned, by good material enabling satisfactory com- 

 parisons to be made. 



In the same paper in which Merycochcerus proprius was described 

 Leidy established the genus Merychyus with three species, Merychyus 

 elegans, Merychyus major, and Merychyus medius. In this same paper 

 Dr. Leidy gave a few of the characters which distinguish Meryco- 

 chcerus from the Merycoidodonts then known. 



l Proc. Acad. A 7 at. Set. Phi/a., 1858, p. 24. 



84 



