258 MOSASAURUS. 



MOSASAUKUS. 



106. One gigantic extinct species of Saurian Reptile has been 

 found to agree with many of the species above cited in the Lacertian, 

 Iguanian, Anolian and Scincoid families of existing Saurians in having 

 the pterygoid bones armed with teeth : but the maxillary teeth com- 

 bine the pleodont with the acrodont characters ; and the skeleton 

 indicates a special adaptation for swimming and a marine life. 



The true affinities of the Mosasaur, the extinct reptile in ques- 

 tion, which was at least twenty-four feet in length, and the remains 

 of which characterize the chalk-formations, were first determined by 

 Cuvier, who places it in the Lacertine group of Saurians between the 

 Iguanse and Monitors. Its dentition exhibits in an eminent degree 

 the acrodont character ; the teeth being supported on expanded coni- 

 cal bases anchylosed to the summit of the alveolar ridge of the jaws : 

 no existing Saurian exactly parallels this mode of attachment of the 

 teeth, either in regard to the breadth of the alveolar border, or in 

 the relative size of the osseous cones to the teeth which they support. 

 A shallow socket is left where the tooth and its supporting base are 

 shed. The form of the teeth is likewise different from that hitherto 

 observed in any existing Saurian : they are pyramidal, with the outer 

 side nearly plane, or slightly convex, and separated by two sharp 

 ridges from the remaining surface of the tooth which forms a half- 

 cone ; the transverse section of the tooth near its attachment to the 

 osseous base presenting the contour given at PL 72, fig. 5. All the 

 teeth are slightly recurved and their peripheral surface is smooth. The 

 teeth are implanted upon the intermaxillary, maxillary and preman- 

 dibular bones ; a series of similarly shaped but much smaller teeth 

 are placed upon the pterygoid bones. The superior maxillary bone 

 in the great cranium preserved in the Parisian Museum — the most 

 celebrated fossil of the present species — contained eleven teeth : 

 Cuvier calculates that the intermaxillary bone may have contained 

 three teeth ; meaning probably three on each side : the premandibular 

 element of the lower jaw supported fourteen teeth : the number of the 

 teeth thus approximating to that which characterizes the Varanus Nilo- 



