E. L. Troxell— Helaletes Redefined. 367 



Helaletes nanus is notable for the rounded molars, the 

 very prominent paracone and receded metacone, the small 

 size, posteriorly, of the ectoloph, and especially for the 

 double internal cusps on the premolars which are most 

 separated on P 3 . P 2 is wider than it is long (7 X 6.3 

 mm.) ; there is a postero-exterior cingulum on each 

 molar, and a conspicuous protocone (antero-exterior) on 

 the upper premolars. 



In this species the maxillary presents a smooth border 

 curved strongly inward above the anterior premolars, 

 indicating a facial pit of a slightly different character 

 from that of H. hoops, described later. 



Helaletes hoops Marsh. 



(Figs. 2-3.) 



Holotype, Cat. No. 11807, Y. P. M. Middle Eocene (Bridger), Grizzly 

 Buttes, Wyoming. 



This genus is readily distinguished from Hyrachyus 

 Leidy, as the latter is generally known, by the small 

 size, the double internal cusps on the premolars, the long 

 diastema in front of the upper canine, the compressed 

 short incisors, the distinctive form of the rounded molars, 

 the great antero-posterior diameter of M 3 , the presence 



Fig. 2. 



J J 807 TYPE Y. P. M. 



Fig. 2. — Helaletes hoops Marsh. Holotype. Showing the upper teeth 

 complete, and the last premolar and three molars of the lower dentition. 

 Xat. size. 



of a heel on M 3 , the absence of connecting ridges between 

 the crests of the lower molars, and finally by the presence 

 of a great facial pit as shown by the smooth edge of the 

 maxillary above the diastema and the premolars. 



