192 BULLETIN 16 9, UXITED STATES NATIONAL MUSEUM 



7DEUTEROGONODON species 



U.S.N.M. no. 9653 includes part of a left maxilla with P*-M' 

 and part of a right mandible with the heel of M3. All the teeth are 

 incomplete and much battered, and none is directly comparable with 

 the types of D. montanus, so that pertinence to that genus and species 

 cannot be established but is probable, at least as far as generic 

 identity .^^ The principal characters exliibited are that P* has a strong 

 conical protocone, somewhat smaller than the external cusp or cusps, 

 and that in the talonid of M3 the three cusps, especially the entoconid, 

 are more distinctly separated than in Mi_2 of the type of D. montanus. 

 These specimens are from Loc. 18, the horizon of which is in doubt 

 but is higher than that of the types of D. montanus and in Fort 

 Union No. 3. 



There are likewise a few tooth and limb fragments, from the type 

 locality, that probably belong to this genus but are of no particular 

 value at present. 



Subfamily Oxyclaeninae Matthew, 1937 (Oxyclaenidae Scott, 1892) 



The oxyclaenine genera of this fauna, Metachriacus, Mimotricentes, 

 Spanoxyodon, Prothryptacodon, and (somewhat doubtfully) Chriacus^ 

 belong with several other Paleocene genera in a very confusing com- 

 plex. The size ranges of their species do not differ greatly, and their 

 morphology is markedly stereotyped in general pattern. Within the 

 Hmits of this general type, however, they seem to ring almost eveiy 

 possible change in combinations of detail, so that they are difficult 

 to distinguish yet are amazingly varied in minutiae and cannot be 

 grouped into one or a few broad but natural genera. The variations 

 involve, among other features: 



1. Placing of the canine (from vertical in Tricentes, etc., to strongly 

 procumbent in Prothryptacodon, etc.). 



2. Number and crowding of premolars and associated develop- 

 ment of diastemata, varying from such types as Metachriacus to 

 Spanoxyodon. 



3. Molarization of P4, from a wholly premolariform type, as in 

 Tricentes (and several other genera) to a submolariform condition as 

 in Spanoxyodon. 



4. Reduction of the paraconid, from strong and distinct (e. g., 

 Deltatherium) to almost indistinguishable (e. g., M2-3 oi Metachriacus). 



5. Placing of the paraconids, from almost strictly internal (e. g., 

 Mimotricentes) to almost strictly median (e. g., Tricentes). 



6. Elevation of the trigonids and their shearing character, from 

 high and strongly shearing (e. g., Chriacus) to low and bunodont 

 (e. g., Tricentes). 



" Dr. Gidley labeled them as of the same species. 



