704 WILLIAM J. SINCLAIR 



The dentition. — The superior incisors are larger than the cor- 

 responding teeth in Elasinognathus bairdii. The inferior incisors 

 are slightly smaller than the superior. Both series have the 

 crowns somewhat cupped, especially so in the superior incisors. 

 The first and second inferior incisors are of equal size, while the 

 third is two-thirds as large as those preceding it. The crowns 

 of both canines are broken off, but the diameters of their roots, 

 measured on the alveolar borders, are greater than the corre- 

 sponding parts of the larger incisors. A long diastema succeeds 

 the canines. The premolars have their anterior cusps united 

 into transverse ridges, slightly notched at the summit. In all 



Fig. I. 



except the second premolar, the ridges are perpendicular to the 

 long axis of the jaw. They are equally developed on the third 

 and fourth premolars. Posterior cross crests are not developed 

 on any of the premolars. In the second premolar, the proto- 

 conid is larger than the deuteroconid and is situated farther for- 

 ward than the latter. In the succeeding premolars, these cusps 

 are of the same size and are situated directly opposite each 

 other. The tetartoconid of the premolars is smaller than the 

 metaconid. The latter cusp is united with the inner side of the 

 base of the protoconid by a ridge. This structure is also found 

 in the molars, all of which have two cross crests. The posterior 

 crest in the first and second molars is somewhat oblique to the 

 axis of the jaw. The third molar is too imperfectly preserved 

 to describe. Anterior and posterior cingula are present on all 

 the molars and premolars. Traces of an external cingulum are 

 found at the outer end of the transverse valley in all except the 

 second premolar. In this tooth the paraconid is very large, 

 uniting by a ridge with the protoconid. In the remaining pre- 

 molars the paraconid is replaced by a style rising but little above 

 the level of the anterior cinofulum. 



