10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 128 



artiodactyls of the Uinta, but I find difficulty in accepting many of 

 his conclusions as to relationships, particularly as portrayed in the 

 rather abbreviated synoptic chart given in this work. As far as the 

 bunodont artiodactyls are concerned there appears to have been no 

 previous attempt at ciphering origins and sequence, although much of 

 the groundwork for this was laid by Sinclair and Peterson. 



Treating first the bunodont forms, I believe these may be logically 

 regarded as representing a single rather large family, the Dicho- 

 bunidae. There would appear to be justification for including the 

 North American forms with those of Europe, although distinct direc- 

 tions and tendencies are noted, inasmuch as basic resemblances are 

 evident suggesting a not too remote common ancestry, possibly in 

 early Eocene or late Paleocene time. It is interesting to note, how- 

 ever, that the schism between the Old World and New World groups 

 appears to have widened with advance in Eocene time, and I see no 

 certain evidence of a later interplay between the hemispheres within 

 the period. 



While including the Eocene bunodonts within the Dichobunidae 

 there are, nevertheless, cogent reasons for recognizing at least three 

 subfamilies among the North American forms, as may be seen in 

 the accompanying chart. The genus Eohyns (Marsh, 1894) is omitted 

 from consideration in this study, as I am unable to determine its rela- 

 tionships or add any information to that brought forth by Sinclair 

 (1914, p. 267), since the type materials are so very incomplete. These 

 are from the lower Eocene (or Paleocene?) of New Mexico. 



An early group, and one which I regard as fundamentally distinct, 

 includes Diacodexis, Wasatchia, and Bunophonis. These are separated 

 under the subfamily Diacodexinae. Wasatchia and the closely related 

 Bunophorus may not much resemble Diacodexis, with their much 

 more inflated tooth cusps, but basically their dental structures are 

 rather similar and together seem rather more condylarth-like than 

 other dichobunids. There is no record of any diacodexids after Lost 

 Cabin time but the suggestion is made that the leptochoerids may 

 have originated somewhere in this subfamily. If the leptochoerids are 

 of North American origin, which I am rather inclined to believe, then 

 of the various dichobunids known here, only the diacodexids on the 

 basis of dentition would seem to qualify (not the helohyids as sug- 

 gested by Scott, 1940, p. 378). Except for relative proportions of the 

 teeth, one cannot escape noticing the basic similarity of the molars. 

 The premolars, moreover, though not so enlarged or so elongate 

 (except in advanced D. secans), would seem potentially qualified, 

 particularly those of the upper dentition. In view of the long interval 



