482 Mr. O. V. Hay on 



somewhat curved, and is occupied by compressed sharp-edged 

 teeth. Of these there are present twenty-eight; but if we 

 restore the bone, as we can safely do, I believe, by aid of 

 Stewart's figures of S. dentatus *, we may conclude that there 

 were originally thirty-four teeth, possibly one or two less. 

 The root of the most anterior tooth has been exposed by the 

 fracture, and its fang is seen to be distinctly faceted ; so 

 that it presents just such an appearance as the tooth of 

 S. lanciformis figured by Leidyf. The roots of teeth situated 

 more posteriorly, whose fangs have been exposed by a tool, 

 are similarly faceted. Cope states J that S. lanciformis is 

 to be distinguished from his S. arapahovius by the lack of 

 facets on the roots of the teeth of the latter. 



Leidy estimated that the maxilla in his hands had sup- 

 ported only twenty-six or twenty-eight teeth, and he was 

 probably correct. That maxilla, a larger one than the one 

 in my possession, seems to have been broken just behind the 

 palatine condyle. If now we take from Leidy's drawing 

 the width of the bone at this point and apply it to the 

 alveolar border, we find that it includes ten teeth ; the width 

 of my own specimen includes thirteen teeth. It is not im- 

 possible, however, that the specimen figured by Leidy had 

 been broken away some little distance behind the condyle. 

 At any rate, 1 do not believe that the difference of a few 

 teeth, other things being alike, would justify us in regarding 

 the specimens as belonging to different species. 



As in the case of the original specimen, there is a shallow 

 groove running along the mesial surface of the maxilla, 

 about 5 millim. from the alveolar border, and from this groove 

 foramina, one for each tooth, enter the bone. 



millim. 



Depth of maxillary at palatine condyle 38 



Distance from anterior end of palatine condyle 

 to hinder end of maxillary 85 



The right mandible is shown in fig. 2, five eighths the 

 natural size and showing the mesial surface. The alveolar 

 border is straight and supports thirty-four teeth, of which 

 those occupying the middle of the border are the largest. In 

 general, they are larger than the teeth of the upper jaw. 

 The line which spans thirteen teeth in the maxilla spans ten 

 in the dentary. At the proximal end of the mandible there 

 must have been a process of the dermarticulare, as in related 



* Kan. Univ. Quart, vii. p. 25, pi. i. figs. 3 a, 4 a. 

 t Trans. Amer. Philos. Soc. xi. pi. vi. fig. 9. 

 % Cretaceous Vertebrata, p. 216. 



