164 



border previous to its outward extension towai-<l the orbit. This is mucli 

 less marked in tlie Clidaatcs propython, but is distinct in M. missuriensis. 



The maxillo-preniaxillary suture gradually descends toward the alveolar 

 border, at the extremity of the maxillary bone, where it descends abruptly, 

 forming an interlocking suture cpiite different from that squamosal type 

 already observed in other species of the order. The length of the premax- 

 illary anterior to this point is three-fourths the length of the same to the 

 beginning of the nares. 



The number of teeth on the maxillary bone was probably thirteen ; 

 twelve alveolae and bases remain, and I add one in the position of the 

 posterior tooth of M. missuriensis, if such existed. This may be questioned, 

 in consideration of the small number of mandibular teeth. Premaxillary 

 teeth, two on each side, the anterior with bases separated only by a groove. 

 Throughout the whole series, the bases of the teeth are considerably more 

 exposed on the inner than the outer side. 



The crowns are everywhere subcylindric at the base; the inner face more 

 convex than the outer. Posteriorly, there is a posterior cutting-ridge, as well 

 as a marked anterior one, both minutely crenulate ; but the former gradually 

 disappears till, in the anterior teeth, there is only an anterior edge, the pos- 

 terior face being convex and continuous with the inner. There is a trace 

 of cutting-edge on the outer portion of the extremity of the crown in the 

 most anterior teeth. The anterior ridge remains very strongly marked. The 

 surface is quite rough with longitudinal ribs, of which eight may be counted 

 on the outer aspect of the second maxillary. These are not strongly marked, 

 and are separated by concave facets. The basal part of the crown is marked 

 by numerous fine, sharp striae, which are most distinct on the inner face. 



The external face of the maxillary bone presents three series of foramina. 

 These rise superiorly on the premaxillary, and increase in number, and become 

 irregular on its extremity. 



The ramus of the mandible is massive, and differs from that of Mosa- 

 saurus giganteus in continuing its proportions to its extremity. Its depth at 

 the latter point is as great as the sixth tooth from the front. It is prolonged 

 beyond the first tooth in correspondence with tlie prolongation of the pre- 

 maxillary. This extremity is conqiressed and obtuse; its inner face is very 

 rugose, as though there had been a closer union at the symphysis than usual, 

 though it would not appear to have been other than ligamentous. The groove 



