1S70.] ^ '^ [Cope. 



The centra of the dorsals are much depressed, quite as in L. perlatus, 

 Cope, and Mosasaurus hrumbyi, Gibbes. Their articular faces are of 

 transverse lenticular form, the siiperior arch being a little more convex 

 than the inferior, and obtusely emarginate for the floor of the neural 

 canal. The superior outline is thus bilobed ; the lobes rounded. The 

 transverse curvature of the articular ball is quite regular, and not, as in 

 Mosasaurus maximus, more steeply inclined at the external or lateral 

 angles. A rather broad, smooth band separates the edge of the ball from 

 the surfaces of the centrum adjacent. The latter are rather finely striate 

 ridged from the edge of this baud. The inferior outline of the centruna 

 is strongly concave, and with two venous foramina separated by a wide 

 interval. The basis of the diapoishysis on a lumbar is very broad, mea- 

 .suring more than half the length of the centrum. In general characters 

 this lumbar resembles the dorsal, including the emargination for the 

 neural canal, but is shortened in relation to its length. 



The depressed form of the lumbar centra gives place gradually on the 

 caudals to a more elevated pentagonal outline, which is still more reduced 

 in width in more posterior regions. The haemal arches are articulated, 

 and on the anterior caudals to slightly elevated bases ; on the more pos- 

 terior, the bases are reduced in height, and more widely and deeply ex- 

 cavated. I have not seen the most distal caudals, and hence cannot de- 

 termine whether their chevron bones articulate in pits, as is the case with 

 those of L. perlatus, L. proriger, etc. On a caudal where the depth of 

 the centrum a little exceeds the transverse diameter, the diapophysis has 

 become narrow and thick. The excavation for the neui'al canal is strongly 

 marked on the more anterior caudal. The smooth border of the articular 

 ball is hei-e narrow, and the superficial rugae are fine, and confined to the 

 anterior part of the centrum. 



Measurements. M. 



Transverse diameter ball posterior dorsal 0.144 



Vertical " . 097 



" " anterior caudal 094 



Transverse " " " 107 



Length centrum caudal 071 



Transverse diameter neural canal 0145 



" " basis diapophysis 083 



" " " " of a more distal caudal 0278 



Longitudinal diameter chevron articulation of caudal 023 



Length centrum 068 



Depth ball centrum 093 



Width " " 091 



Length centram of a lumbar 106 



"Width of articular ball 125 



In instituting a comparison between this and other known Mosasauridse, 

 it will be necessary to consider species refei-red to Mosasaurus as well as 

 to Liodon, from the fact that some of the former may really be Liodons. 



