NO. 6 PALEOCENE FAUNAS OF BISON BASIN — GAZIN 49 



the characteristic "V" and "W" shapes to the outer cusps are not so 

 transversely extended as in Titatioides, or the more extreme condi- 

 tion seen in Archaeolambda. The relatively great width is composed 

 largely of the talon, and in the molars, as clearly shown in M-, there 

 is a strong ledgelike cingulum about the lingual and posterior margin. 

 On Titanoides molars the lingual cingulum is weak, although better 

 developed along the posterior margin of the premolars than in Caeno- 

 lambda. The molars of Caenolambda would appear to be about equal 

 to one another in size as in Pantolambda, not showing the marked 

 increase from M^ to IVP seen in Titanoides, or the reduction of M^ 

 noted in Barylambda and Haplolambda. 



The skull of Barylambda is large and relatively broader than that 

 of Caenolambda. The nasal cavity is larger and the nasal bones much 

 wider. The frontals are broad in both forms, but Barylambda does 

 not exhibit a sagittal crest so heavy and prominently arched as in 

 Caenolambda. The teeth of Barylambda are transversely broad in 

 comparison to their anteroposterior dimension, as in Caenolambda, but 

 the talon of molars, particularly M^ and M^, is not nearly so slender ; 

 moreover, the cingulum is weak or absent lingually rather than shelf- 

 like. M^, as noted above, is much reduced in Barylambda. 



The comparisons between Haplolambda and Caenolambda are 

 rather similar to those between Barylambda and Caenolambda, 

 although the species Haplolambda quinni and Caenolambda pattersoni 

 are more nearly comparable in size. The cranial portion of Haplo- 

 lambda is shorter and the sagittal crest not so arched as in Caeno- 

 lambda, but the nasals are wider and the nasal cavity larger although 

 the frontals are not so broad. The cheek teeth resemble those of 

 Caenolambda in their relative width and the distinctly labial position 

 of the primary external cusps, but again as in Barylambda the molar 

 talons are not so slender, the cingulum is lingually weak, and M^ is 

 reduced. In Haplolambda, moreover, M^ would appear to be larger 

 than M^, quite the reverse of Titanoides. The comparatively small 

 canine in Haplolambda would appear to be a striking difiference from 

 both Caenolambda and Titanoides, but the size of this tooth is so often 

 a matter of dimorphism that one hesitates to stress the character. 

 Nevertheless, if there is any dimorphism in this respect within species 

 of Coryphodon, it is certainly much less evident. 



CAENOLAMBDA PATTERS0NI,22 new species 

 Plates 12-14 

 Type. — Skull, lacking zygomatic arches and mandible, U.S.N.M. 

 21036. 

 22 Named for Bryan Patterson in appreciation of his work on the pantodonts. 



