190 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



description of this specimen, in which it is placed in a new species. 

 Apparently it was at first placed in Claenodon with a query, and later 

 the generic name was erased and another, which appears to be new, 

 substituted, but no corresponding change was made in the description, 

 and the genus was not defined. I do not believe this to be adequate 

 for the definition of either genus or species and feel obliged to suppress 

 these manuscript names. The specimen is aberrant (with respect to 

 species of Claenodon) in several details, but their significance cannot be 

 judged and comparative Fort Union material is too scanty for good 

 diagnosis. It is, for instance, entirely possible that this belongs to 

 Claenodon latidens.^^ 



Genus DEUTEUOGONODON Simpson 



Deulerogonodon Simpson, 1935d, p. 232. 



Type. — D. montanus (Gidley). 



Distribution. — Middle Paleocene, Fort Union, Montana. 



Diagnosis. — Dentition basically arctocyonid in type, and resembling 

 Protogonodon and Claenodon. Small, distinct, cingulum hypocone on 

 M^~^ (at least), cingula almost completely circling these teeth. Sm.all 

 but well-defined mesostyle present. Parastyle of M^ a distinct cusp, 

 crowning a lobe projecting strongly externally. Lower molars with 

 trigonid only slightly higher than talonid, metaconid smaller than but 

 as high as protoconid. Paraconid very small but distinct, subconical, 

 on slope of metaconid directly anterior to its apex. Talonid basin 

 open, crescentic lophid continuous but crest differentiated into hypo- 

 conid, hypoconulid, and entoconid, progressively smaller in that order. 

 Enamel wrinkled, but all cusps clear-cut and little or no tendency to 

 form crenulations or accessory cuspules. 



Discussion. — This seems to be a very distinctive genus, at once 

 distinguished from any similar form by the presence of a mesostyle. 

 The combination of the other characters given is equally distinctive, 

 although individually they are less so. The genus could be a deriva- 

 tive of Protogonodon, although it is too incompletely known and too 

 distinctive to establish this as a definite theory. I know of no Torre- 

 jon genus that compares more closely than the probably related but 

 manifestly distinct Claenodon, and none of the lower Eocene arctocyo- 

 nids could be derived from Deuterogonodon. The possibility that 

 Phenacodus was derived not from Tetraclaenodon, as commonly sup- 

 posed, but from Protogonodon by way of a form something like Deu- 

 terogonodon is worthy of consideration but cannot be very seriously 



»« Dr. Qidley may have had the same idea, and his manuscript is perhaps older than the publication of 

 1919. The specimen was collected before the type of C. latidens and was obviously in Dr. Oidley's hands 

 when he wrote his claenodont paper, so that its omission may well be due to his having decided that the 

 specimen did not warrant a new name. 



