36 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 91 



shadows the protoconule and metaconule. The anterior portion of 

 the tooth is relatively wide and projects outward somewhat as in 

 Tetradaenodon and shows a prominent parastyle. The external 

 cingiilum is much weaker than in Prolog onodon and is peculiar in 

 being discontinuous across the postero-external portion of the para- 

 cone; however, there is no mesostyle such as observed in Tetradae- 

 nodon and the cingulum is perhaps a little better developed postero- 

 external to the metacone than in Tetradaenodon. 



M? is relatively small as in Tetradaenodon^ more reduced than in 

 Protogonodon, but the cingulum is continuous around the inner wall 

 of the protocone as in the latter and there appears to be little or 

 no evidence of a distinct hypocone. 



The lower teeth of the type are from both rami and between 

 them include a representation of the series from P3 to M3. Although 

 rather well worn, many characters can be ascertained showing, as 

 with the upper dentition, the structural position that this form 

 holds between Protogonodmi and Tetradaenodon. 



P3, though incomplete posteriorly, is seen to be small and narrow, 

 comparable in this respect to Protogonodon., but with a more gently 

 sloping posterior crest. 



P4, though slender and relatively small, shows a marked resem- 

 blance to T etradaenodon. The parastylid is high, prominent, and 

 deflected inward from the anterior crest of the protoconid about 

 as in Tetradaenodon. The tooth is well worn, but from the outlme 

 of the occluding surface there is little doubt that a pronounced 

 metaconid was present. The heel structure is nearly as in Tetra- 

 daenodon but with less anteroposterior extent and a less distinct 

 entoconid. 



Ml is too worn to show any important characters but as in the 

 succeeding tooth shows the talonid to be less widely basined than in 

 Protogonodon. 



In M2 the trigonid portion exhibits a more prominent paraconid 

 than in Tetradaenodon.^ which is perhaps not so close to the meta- 

 conid, but as in the latter it is distinctly lingual in position and is 

 joined by an arcuate crest to the anterior slope of the protoconid, 

 forming a somewhat more distinct but anteroposteriorly restricted 

 trigonid basin than in Protogonodon pentacus. 



M3 is relatively small as in Tetradaenodon but with a much better 

 developed paraconid. The trigonid is anteroposteriorly shortened 

 and the paraconid more lingual in position than in Protogonodon. 

 The talonid basin is relatively simple, with the entoconid and hy- 

 poconulid not actually distinct but forming a slightly cuspate crest. 



Remarks. — The intermediate position of Desmatodaenus between 

 Protogonodon and Tetradaenodon suggests that Tetradaenodon may 



