163 



IncbcR. 



Proximal, width of the cup 3.43 



Proximal, depth of the cup 3. 23 



Caudal without the diapophyses, No. 1, length 1.6 



Caudal without the diapophyses, No. 1, depth of the cup 2. 65 



Caudal without the diapophyses, No. 1, width of the cup 2. 6 



Caudal without the diapophyses, No. 1, height of the neural canal 0.4 



Caudal without the diapophyses, No. 1, antero-posterior width of the neural spine 0. 8 



Caudal without the diapophyses, No. 2, length 1.2 



Caudal without the diapophyses, No. 2, depth of the cup 2.15 



Caudal without the diapophyses, No. 2, width of the cup 1.86 



Caudal without the diapophyses, No. 2, width of the neural spine (antero-posterior) 1. 07 



Caudal without the diapophyses, distal, length 0. 5 



Cauual without the diapophyses, distal, depth of the cup 0.85 



Caudal without the diapophyses, distal, width of the cup 0. 64 



Caudal without the diapophyses, distal, antero-posterior diameter of the neural spine 0. 40 



The points of attachment of the chevron-bones on the distal vertebrae 

 are strongly-marked pits ; on the anterior, the anterior margins of the pits 

 are raised and continuous with the chevrons. 



The muzzle presents the usual characters of the large Mosasauroids, but 

 adds a peculiarity in the prolongation of the premaxillary bone into a cylindric 

 mass, forming an obtuse beak beyond the premaxillary teeth. The bone is 

 narrowed anteriorly, and does not descend regularly, as in Mosasaurus, sp., 

 but continues to its abrupt and narrowed termination described. The 

 extremity is deeper than wide. Immediately in front of and between the 

 anterior premaxillary teeth, a short acuminate projection interrupts the 

 surface, and, in front of this, a transverse depression. Above, the surface 

 becomes flattened, and presents two shallow longitudinal depressions con- 

 tinuous with the nostrils. Where the premaxillary rather suddenly contracts 

 into its spine, it is materially wider than the maxillary on each side of it ; in 

 M. missuriensis it is narrower, according to Goldfuss. The maxillary border 

 of the nares is rather suddenly concave at the anterior extremity of the 

 nares, narrowing the maxillaries. The latter gradually widen by the expan- 

 sion of their inner margins. 



No part of the fronlals is preserved, but a considerable part of the left 

 prefrontal remains. It unites by a very coarse, overlapping suture with the 

 maxillary, whose outline forms an irregular chevron, with the apex pointing 

 forward in the middle of the maxillary bone. This, it will be seen, is very 

 different from the form given by Goldfuss in the M. missuriensis, where the 

 most anterior point of the suture is on the nareal margin. The external 

 margin of the bone behind, is contracted considerably within the maxillary 



