118 M. R. Thorpe — New Forms of Agriochoerus. 



nasals pointed posteriorly. Middle Oligocene (lower 

 Brule) A. antiquus antiquus Leidy. 



Size about equal to that of Eporeodon major; bullae small ; 

 palate nearly flat; palatonarial border opposite poste- 

 rior edge of M^ ; nasals pointed posteriorly ; four supe- 

 rior premolars. Upper Oligocene (middle John Day). 



A. guyotianus Cope. 

 6. Infraorbital foramen unknown. 



Size largest of this genus; four premolars; sagittal crest 

 low and broad; brachyodont; P^ two-rooted ; antero- 

 posterior diameter of molars greater than transverse. 

 Lower Oligocene (Pipestone Creek). 



A. maximus Douglass. 



Size smallest of the genus; P^ right triangular; P* equi- 

 laterally triangular in cross-section ; molars broader 

 than long ; M^ and M^ possess internal cingula. Lower 

 Oligocene A. minimus Douglass. 



Species large ; buUas large ; nasals narrow and pointed pos- 

 teriorly (Wortman) ; palatonarial border opposite ante- 

 rior cusp of M^; three superior premolars. Upper 

 Oligocene (Protoceras beds) A. auritus Leidy. 



Species about size of A. latifrons; (known from single 

 molar tooth). Middle Miocene (lower Manchhars). 



A. sp. Lydekker. 



Eeferences. 



Cope, E. D. 1879. A. On some characters of the Miocene fauna of Oregon. 



Proc. Amer. Philos. Soc, 18, 63-78. 

 — 1879. B. Second contribution to a knowledge of the Miocene fauna of 



Oregon. Ibid., 370-376. 

 — 1881. On the Nimravidae and Canidse of the Miocene period. U. S. 



Geol. Geog. Survey, 6, 165-181. 

 — 1884. Synopsis of the species of Oreodontidse. Proc. Amer. Philos. Soc, 



21, 503-572. 

 Douglass, Earl. 1902. Fossil Mammalia of the White Eiver beds of 



Montana. Trans. Amer. Philos. Soc, new ser., 20, 237-279. 

 Leidy, Joseph. 1850. Descriptions of Ehinoceros nehrascensis, Agriochoerus 



antiquus, Palceotherium proutii, and P. bairdii. Proc. Acad. Nat. Sci., 



Phila., 5, 121-122. 

 — 1852. Description of the remains of extinct Mammalia and Chelonia from 



Nebraska Territory. In D. D. Owen, ^'Eeport of a geological survey 



of Wisconsin, Iowa, and Minnesota, ' ' etc., 534-572. 

 — 1854. The ancient fauna of Nebraska. Smithson. Contrib. to Knowl., 



6, art. 7, 1-126. 

 — 1856. Notice of some remains of extinct vertebrated animals. Proc. 



Acad. Nat. Sci. Phila., 8, 163-165. 

 — 1869. The extinct mammalian fauna of Dakota and Nebraska. Jour. 



Acad. Nat. Sci. Phila. (2), 7, 1-472. 

 — 1871. Eeport on the vertebrate fossils of the Tertiary formations of the 



West. 2d (4th) Ann. Eept.. U. S. Geol. Survey Wyoming and Terr., 



340-370. 



