278 Thorpe — New Genus of Oligocene Hycenodontidce. 



the smallest species. H. minutus Douglass is omitted 

 from the synoptic table, for the type consists of only a 

 right M 2 and the taxonomic position of the species is 

 uncertain. Matthew has referred it to Pseudopterodon, 

 and yet Scott believes that this genus was established on 

 the milk dentition of Hycenodon. This M 2 probably 

 belongs to a creodont, but its reference to Hycenodon 

 seems to me to be doubtful. 



Description of Species. 



Neohycenodon, gen. nov. 



Distinguishing Characters. — Larger than Hycenodon, 

 dolichocephalic, glenoids far below basicranial plane, 

 basicranial region foreshortened, dentition similar to 

 Hycenodon, except for the antero-external buttress on the 

 paraconid of M 3 . 



Neohycenodon horridus (Leidy) 1853. 



(Figs. 1, 2.) 



Y. P. M. 



Fig. 1. — Neohycenodon horridus (Leidy). Left lateral view of skull. 

 X about 1/3. 



Two very excellently preserved skulls with jaws repre- 

 sent this genus and species in the Marsh Collection. Cat. 

 No. 12766 has been selected as a cotype of the genus. It 

 was collected in South Dakota, and, while fully mature, 

 yet its sutures are clearly shown in detail. The other 

 specimen, Cat. No. 10074, collected near Eed Cloud, 

 Nebraska, is an old individual and is unique in that it is 

 the largest complete skull of this species so far reported. 



