174 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



fies, but its adaptive characters, at least, are more arctocyonine and 



the groups are more easily defined if it is placed here. It may not 



really be a creodont. 



Genus CLAENODON Scott 



Claenodon Scott, 1892, p. 298. 

 Synonym: Neoclaenodon Gidley, 1919. 



This group was studied by Dr. Gidley and the results published 

 (1919), his manuscript notes including no further observations. One 

 specimen, of considerable interest, has since been added to the Na- 

 tional Museum collection (by Silberling and me in 1932), and there are 

 several specimens in the Princeton collection that were not included 

 by Gidley in his publication. Dr. Gidley also studied Cope's types 

 and at least two later American Museum Torrejon specimens (A. M. 

 nos. 16543 and 16545), but he apparently did not examine the whole 

 American Museum series, wliich includes about 50 specimens. On 

 this basis I am forced to adopt a broader view of the variability of 

 the group and to modify the generic and specific criteria used, thus 

 arriving at a modified systematic arrangement, which also differs from 

 the final conclusions of Dr. Matthew (Pale. Mem.), based on American 

 Museum material only. 



With one exception, the Fort Union specimens were all referred by 

 Gidley to a new genus, Neoclaenodon. The supposed generic char- 

 acters as given by Gidley (1919, p. 547) may be listed and commented 

 on as follows: 



1. "Cranial portion of skull relatively long and deep; interorbital 

 space apparently much narrower, and postorbital constriction longer 

 and more slender than in Claenodon." This is based on a comparison 

 of two specimens, one of Claenodon "corrugatus" and one of "Neo- 

 claenodon" montanensis, as no others yet discovered show these 

 features. They are crushed in opposite ways, which accounts for 

 part of the difference in aspect. Tliis individual of "N." montanensis, 

 however, probably does have a slenderer and longer midcranial region, 

 but this is a character so variable with age, so likely to be of merely 

 specific value at best, and so impossible to use on a practical basis 

 for the separation of the fossil species that, in itself, it does not carry 

 generic weight. 



2. "Anterior premolars, upper and lower, much reduced; in upper 

 jaw distinct diastemae behind P', and between P^ and P^; the first 

 premolar, above and below, lies closely appressed to the canine." 

 This is in part distinctive from some specimens of C. Jerox, and not 

 from others. The influence of selecting particular specimens for 

 comparison is seen in the fact that Matthew (Pale. Mem.) proposed 

 to redefine Neoclaenodon as having the premolars unreduced [relative 

 to Claenodon]. In fact the whole series with its various species is 

 variable in these characters and varies, as far as apparent, about a 



