480 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 41. 



ing back only to the third tooth. The vertical part of this border is 

 but a little shorter than the oblique portion. Back of this border, 

 above the fifth tooth, is a rounded, free, emarginate edge marking 

 the outer boundary of the narial opening. On the outer surface are 

 two parallel rows of foramina, those of the lower row leading into the 

 bases of the teeth. The border meeting the prefrontal is missing. 



Measurements of maxilla. 



mm. 



Greatest length as preserved 248 



Greatest width over ninth tooth ■ 55 



Greatest width over second tooth 34 



Width from alveolar border to narial border 51 



Dentition. — In the maxillary there is evidence showing the pres- 

 ence of at least ten teeth, and the posterior end of this bone, which 

 is missing, may have contained one or two more. (See pi. 40.) 



Counting from the front, the first, second, fourth, and tenth teeth 

 were lost in fife, only the empty cavities remaining; the third, fifth, 

 and eighth are represented by the broken bases of the crowns; the 

 seventh and ninth, both mature teeth, are present and in a good state 

 of preservation, as are the second, fourth, fifth, and sixth germ teeth. 

 The dental series is well shown in plate 40. 



The ninth maxillary tooth has a bulbous crown with a finely 

 wrinlded enamel surface. This wrinkling of the enamel is coarsest 

 at the apex and descending becomes gradually finer, ending in a 

 nearly smooth surface on the lower constricted part of the tooth. 

 As in all mosasauroid reptiles the tooth is attached to a spheroidal 

 mass of ostein. On the posterior side of the ninth tooth there is a 

 very faint carina which fades out before reaching the apex. The 

 apex is worn. 



The seventh tooth is slightly smaller in transverse diameter, with 

 a more pronounced posterior carina. The shape of this tooth also 

 differs from the ninth by a shallow depression encircling the base of 

 the crown just above the more constricted neck, which meets the 

 ostein base. 



As shown by the broken crown, the fifth tooth has a similar encir- 

 cling depression of the crown. The base of the eighth indicates that 

 that tooth resembles the ninth more closely than it does those pre- 

 ceding it. 



On the inner side of the dental border of the maxillary there are 

 the usual pits or excavations, several of which contain young teeth 

 in various stages of development. 



The young tooth showing in the sixth socket appears to be more 

 elongate vertically, with anterior and posterior carinas which termi- 

 nate in a slightly raised point on the apex of the tooth. The position 

 of the carinse on the inner and outer sides of the tooth, which is just 

 emerging above the parapet of the jaw, appears to indicate a revolv- 

 ing movement of the tooth as it rises into place. 



