1G3 



Inches. 



Proximal, wiiltli of the cup ]' ' 



Proximal, <lci>tli of the cup ' • '■ 



Caiulal wit bout tlio diapopliyses, No. 1, leiisHi '• ' 



CaiKlal witliout tlie diapophyses, No. 1, deptli of tliocup '-J- *j-J 



Caiulal without tho diapophyses, No. 1, width of the cup 2.6 



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



Caudal without tho diapophyses, No. 1, antero-posterior width of tho 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 tho cup 1-S<5 



Caudal without tho diapophyses. No. 2, width of the neural spine (antero-posterior) 1.07 



Caudal without the diapophyses, distal, leugth 0.5^ 



Caui'.al without the diapophyses, distal, depth of the cup. 0.8.5 



Caudal without tho diapophyses, distal, width of tho cup 0.64 



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



The points of attachnieut 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 uf the large Mosasauroids, but 

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

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

 narrowed anteriorly, and does not descend regularly, as in Mosasaurm, 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 projectioQ 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 graxlually wulen 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 narcal margin. The external 

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



