Cope.l ^"0 [Jan. 18, 



Front narrower ; internal wall of fourth premolar not com- 

 plete A. antiquus. 



Front wider ; skull shorter and higher ; internal wall of inferior 



P-m. iv complete A. latifrons. 



aa. Foramen infraorbitale above junction of P-m. ii and iii. 



Front medially concave, laterally descending to orbits ; sagit- 

 tal crest short A. trifrons. 



II. Otic bullae mammiform with triangular base. 



Front convex ; nasal bones acute posteriorly ; fourth inferior 

 premolar complete ; infraorbital foramen above junction of 

 P-m.. iii and iv A. guyotianus. 



III. Otic bullae oblong, constricted at the middle. 

 Infraorbital foramen above j unction of P-ms. ii and iii ; front 



plane ; nasal bones truncate posteriorly ; postglenoid pro- 

 cess robust A. ryderanus. 



Besides the above, Leidy has described an A. major* as near to the A. 

 antiquus, but of larger size. Marsh has described a small species from the 

 Uinta formation under the name of A. pumilus.\ Lydekker figures and de- 

 scribes a superior molar tooth from India as probably belonging to this 

 genus. \ It is stated by him to have been found in the earlier pliocene for- 

 mation. If this determination be correct, it represents the latest known 

 species, as the A. pumilus of Marsh is the earliest. Owing to incomplete- 

 ness in the descriptions of these species I cannot include them in the above 

 synoptic table. 



Agriocneerus antiquus Leidy. 



Proceedings Academy Philadelphia, 1850, 121 ; 1853, 392 ; 1854, 157 ; 

 1857, 89, Ancient fauna of Nebraska, 1853, p. 24, PI. I, figs. 5-10. Bronn 

 Lethsea Geognostica, 1856, 933 ; Leidy Extinct Mammalia Dakota and 

 Nebraska, 1869, 132, PI. XTII, fig. 4. 



White River epoch of Nebraska and Dakota. 



Agriochoerus major Leidy. 



Proceedings Academy Philadelphia, 1856, p. 164 ; 1857, 89. ? Eucro- 

 taphus auritus Leidy, Owen's Report Geological Survey, 1852, p. 563, 

 PI. XV, figs. 1-3. Ancient Fauna of Nebraska, 1853, p. 56 ; PI. VII, 

 figs. 1-3. Bronn Lethsea Geognostica, 1856, 931. 



White River formation of Dakota and Nebraska. 



Agriochoerus latifrons Leidy. 



Proceedings Academy Philadelphia, 1867, p. 32. Extinct Mamm. 

 Dakota, Nebraska, 1869, p. 135, PI. XIII, figs. 1-3. 



White River epoch of Dakota and Nebraska. 



♦Extinct Mammalia of Dakota and Nebraska, p. 134. 

 t Amer. Journal Science and Arts, 1875, p. 250. 

 JPaleontologica Indica. 



