404 GEOLOGICAL SURVEY OF THE TERRITORIES. 



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 disappears till in the anterior teeth there is only an anterior 

 edge, the posterior 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 for- 

 amina. These rise superiorly on the premaxillary, and increase in num- 

 ber 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 the pro- 

 longation of the premaxillary. This extremity is compressed 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 for Meckel's cartilage is very large 

 and has been exposed below the last two teeth, as the splenial terminates 

 at the third. Two series of foramina on the external face of the ramus. 

 There are alveolae and bases for thirteen teeth on the dentary bone. 

 This, it will be observed, is one more than in M. gracilis, and one less 

 than in other species of Mosasaurus. The posterior extremity of the 

 dentary shows its marks of reception into the notch of the coronoid ; it 

 is more compressed and less club-shaped than the corresponding part of 

 M. mitchilliiy and would indicate less lateral flexibility than in some 

 other types. 



The right pterygoid is of less elongate form than in some other species. 

 It presents the sutural face for union with the palatine on the outer an- 

 terior extremity, and narrows to an apex a little in advance. The den- 

 tigerous face is widest at the anterior third the length, where the outer 

 margin is expanded. This then contracts and is compressed vertical at 

 the tenth tooth, where it is broken off. The transverse process is given 

 off a little anterior to the ninth tooth. The interior face of the bone is 

 a vertical plane, without projection, except a slight obliquity at the an- 

 terior extremity, and it is clear there has been some interval between 

 this pterygoid and its fellow. The superior margin is obtusely rounded. 



The bases of the pterygoid teeth are exposed for two-thirds their 

 length, on the outer side of the bone, thus approaching the Platecarpus. 

 The antero-median are large, and the anterior most closely placed. 

 Their crowns are strongly recurved, round in section, and with a fine 

 sculpture of straight striae, most marked near the base and on the inner 

 side. They are more spaced posteriorly than any other species except 

 M. mitchillii, and are relatively larger than in any except the same 

 species. They have not the compressed form with basal shoulder, 

 characteristic of the M. deltayi. 



Measurement of muzzle. 



Inches. 



Length of fragment 31. 



Length from end muzzle to pre-frontal 21. 5 



Length from end muzzle to nares 11. 75 



Length from eud muzzle to maxillary 5. 75 



