Troxell — Hyrachyus and its Subgroups. 



45 



and posterior cross crests. In the worn condition these 

 crests come to show the typical "L" of the rhinoceros- 

 like animals because of the low ridges extending from 

 them on the onter forward side. The ridge from the 

 anterior crest continues on into an upfolded edge or 

 cingulum. 



Fig. 4. 



J1170 TYPE 



Y. P. M 



Fig. 4. — Holotype, Hyrachyus affinis gracilis, subsp. nov. Crown views of 

 the upper and lower teeth. Note the odd-shaped P 4 and M 3 and the rhinoc- 

 eroid lower teeth with the strongly L-shaped cross crests. Nat. size. 



This new subspecies is put under H. affinis (Marsh) 

 on account of the agreement in size. Such parts as can 

 be compared exhibit some notable differences : the new 

 form may be distinguished (1) by the weaker paracone 

 on M 3 , which blends into the metacone without such a 

 deep groove on the outer side ; (2) by the less prominent 

 base of the metacone, giving a more nearly rounded out- 

 line to the posterior and outer sides; and (3) by the 

 longer P 4 with its heavier metaloph continuous with the 

 end of the curved protoloph. 



Hyrachyus princeps Group. 



Hyrachyus eximius Leidy 1871. 



Hyrachyus princeps Marsh 1872. 



Hyrachyus imperialis Osborn, Scott and Speir 1878. 



These species are grouped together because they can 

 not be distinguished specifically. Leidy 's type was the 



