169 



for union with the pterygoids, and the superior posterior process terminates 

 iu an acute cone. In front of the articulation, the bone is a vertical plate, 

 slightly concave on the inner side ; the anterior half is silbquadrate in section ; 

 the outer face subvertical ; the inner regularly rounded. The inferior surface 

 is marked with a groove which passes from the inner side to the outer. The 

 portion on the outer side of this groove is on the distal third of the bone pro- 

 duced downward into a prominent keel or ridge. The anterior extremity is 

 an acute point. Each bone bears eleven teeth, all of which have the external 

 faces of their roots exposed. The bones are curved outwardly from the fourth 

 tooth from behind ; opposite the sixth, there is a longitudinal concavity on 

 the inner face. 



The occipital region and suspensoria are not present, but both quadrates 

 were found perfectly preserved, excepting the thin ala. They present marked 

 characters, being most nearly allied to those of L. proriger and L. validus. 

 The proximal articular surface exhibits, an obliquity in the transverse direc- 

 tion. It presents a large internal angle, which, instead of being nearly at 

 right angles to the axis of the main portion of the surface, is nearly in the 

 same line. The decurved posterior hook is very short. The distal articular 

 surface has, like that of other Liodons, a small transverse extent, and is divided 

 by a concavity into two tuberosities. The outer of these receives at its angle 

 the prominent narrow portion of the internal ridge, which extends from the 

 internal proximal angle. The prominence of this ridge is greater than in any 

 other species except L. proriger ; it is acute throughout its length, and has a 

 gentle sigmoid flexure. The basis of the great ala includes a smaller area than 

 usual, and is continuous with a prominent narrow ridge, which proceeds from 

 outside the meatal crest. This meatal crest takes the place of the " knob '' in 

 such Mosasauri as M. dekayi; it projects strongly backward and outward as an 

 angle of two ridges, the inferior being acute and curved, and terminating above 

 the middle of the distal condyles. The meatal pit is not concealed between 

 ridges, but is internal ; its form is peculiar, being a narrow oval, three times 

 as long as wide, directed downward and forward. Thus, the characters of 

 this element are well marked among those pertaining to the other species. 



The teeth are not much compressed, and have a cutting angle on the 

 anterior and posterior margins, which separate nearly equal faces. 



The vertebral centra change in form from the anterior to the posterior 



regions. The ball of the axis is round ; those of the vertebra early succeed - 

 22 c 



