560 F. B. Loomis — New Mosasaur from the Ft. Pierre. 



raised in a low rounded ridge, so that between this and the 

 external rim there is a shallow channel. On the inner surface 

 the margin of the meatus is beveled and the external edge 

 rounded. The large oval stapedial pit is situated very high 

 up (see fig. 2) as in Brachysaurus and Platecarpus, lying at the 

 upper end of the meatus notch. 



Height of the quadrate 103 mm 



Greatest width of quadrate 88 mm 



Fig. 2. 



Fig. 2. 

 nat. size. 



The quadrate from the inner side showing the stapedial pit. 1/2 



The lower jaw is unusually long and fairly slender, and car- 

 ries in my specimen 7 teeth with places for four more, making 

 a total of 11 teeth for the dentale. This bone projects a short 

 distance in front of the first tooth and extends back so as to 

 make over half of the mandible. Externally it is ornamented 

 with longitudinal strise. The splenial (presplenial) is exposed 

 externally only below the posterior end of the dentale. The 

 artieulare is large and extends from the rear of the dentale 

 back beyond the articular fossa. In this species is found but 

 very little of the articular fossa, that being carried mostly by 

 the supra angulare. This latter bone is unusually large, cover- 

 ing almost all the space back of the dentale and above the 



