NO. 6 PALEOCENE FAUNAS OF BISON BASIN — GAZIN 47 



conspicuously in the collections. The form represented may be 

 Phenacodus? grangeri which Simpson (1935c) described from the 

 Colorado Tiffany, but the measurements where equivalent materials 

 are present noticeably exceed those of the more southern animal. 

 M3 which measures 13.6 by 9.2 mm., for example, is 19 percent longer 

 and 12 percent wider. This difference in a form such as Phenacodus 

 might not be important. The significance would, of course, depend 

 on the position of these two examples with regard to their respec- 

 tive but unknown means. 



The third lower molar apparently reveals no information as to 

 whether references should be made to Phenacodus or Tetraclaenodon. 

 P^, however, as in P. ? bisonensis has a well-developed posterointernal 

 basin and the tritocone is apparently better defined than usual in 

 Tetraclaenodon puercensis. The isolated M^ has a distinct but small 

 mesostyle and the hypocone is particularly small. 



PANTODONTA 



CORYPHODONTIDAE 



TITANOIDES PRIMAEVTJS Gidley, 1917 



Plate II, figure 5 



The finding in North Dakota by a party under the direction of 

 Dr. Glenn L. Jepsen of portions of the skull including the upper denti- 

 tion belonging beyond doubt to the type of Titanoidcs primaevus was 

 unusually good fortune, so that no uncertainty now exists as to the 

 characteristics of the superior dentition of this upper Paleocene panto- 

 dont. Patterson early (1933) described new materials from the Pla- 

 teau Valley beds of Colorado as representing Titanoides, but upon later 

 discovery of at least three pantodont forms from these beds, with 

 distinguishing features in the upper dentition, was forced to regard 

 all as distinct from Titanoidcs and the species at first referred to Tita- 

 noides was given the new generic name Barylambda. It now develops, 

 with the finding of Titanoides upper teeth, that while Barylambda and 

 Haplolambda are clearly distinct, Sparactolambda -° is the form which 

 I believe must now be regarded as the synonym of Titanoides. 



In the University of Wyoming material from the Bison basin there 



-^ Jepscn's discovery has likewise permitted us to determine correctly the 

 identity of an excellent pantodont skull collected by Dr. T. E. White in 

 McKenzie County, N. Dak., and, like the type of T. primaevus, from the general 

 area of the type Fort Union. This skull, originally and with apparent correct- 

 ness, determined by White as representing Sparactolambda, is now seeu to belong 

 beyond doubt to Titanoidcs primaevus. 



