M. R. Thorpe — Neiv Forms of Agrioclueriis. 117 



site anterior lobe of M^,- nasals pointed posteriorly; 

 four superior premolars. Middle Oligocene (lower 

 Brule) A. antiquus dakotensis, subsp. nov. 



About same size as above ; bullae large ; palate gently eon- 

 cave ; palatonarial border opposite anterior part of I\P ; 

 nasals acute posteriorly; four superior premolars. 

 Upper Oligocene (middle and upper John Day). 



A. irifrons Cope. 



Skull size of second above; bullae small; palate gently 

 concave; palatonarial border opposite posterior lobe of 

 M2 ; nasals blunt posteriorly ; three superior premolars. 

 "Upper Oligocene (middle and upper John Day). 



A. ferox (Cope). 



2. Infraorbital foramen above anterior lobe of P^. 



Skull about size of Eporeodon major; bullae large and 

 medially constricted; palate strongly concave; palato- 

 narial border acute and opposite middle of M'^ ; nasals 

 broadly rounded posteriorly; four superior premolars. 

 Upper Oligocene (middle John Day). 



A. ryderanus Cope. 



3. Infraorbital foramen above middle of P^. 



Somewhat larger than 0. culhertsonii; bullae large; pal- 

 ate flat ; internal wall of P* complete ; either three or 

 four superior premolars. Middle Oligocene (lower 

 Brule) A. latifrons Leidy. 



Skull about size of that of Eporeodon major; bullae 

 unknown ; palate nearly flat ; palatonarial border oppo- 

 site posterior part of M^, ; nasals rounded posteriorly; 

 three superior premolars. Upper Oligocene (middle 

 and upper John Day) A. macrocephalus (Cope). 



Size about that of 0. culhertsonii; bullae moderately large 

 and inf eriorly keeled in transverse plane ; palate steeply 

 inclined ; palatonarial border opposite anterior part of 

 M^ ; nasals obtuse posteriorly ; three superior premo- 

 lars. Upper Oligocene (upper John Day), 



A. hullahis, sp. .nov. 



4. Infraorbital foramen above posterior part of P^. 



Skull about size of second above ; bull^ unknown ; palate 

 gently concave; palatonarial border opposite middle of 

 M^ ; nasals rounded posteriorly ; three superior premo- 

 lars. Upper Oligocene (Protoceras beds). 



A. migrans (Marsh) . 



5. Infraorbital foramen above interval between P^ and P^ 



Size slightly greater than 0. cidhertsonii; bullae moder- 

 ately inflated; palate strongly uparched anteriorly; 

 internal wall of P^ incomplete; four superior premo- 

 lars ; palatonarial border opposite anterior lobe of M^ ; 



