168 MARINE SAURIANS. , 



chalk formation, the Ichthyosauri and Plesiosauri were the 

 tyrants of the ocean ; and just at the point of time when 

 their existence terminated, during the deposition of the chalk, 

 the new genus Mosasaurus appears to have been introduced, 

 to supply for a while their place and office,* being itself des- 

 tined in its turn to give place to the Cetacea of the tertiary 

 periods. As no Saurians of the present world are inhabi- 

 tants of the sea, and the most powerful living representatives 

 of this order, viz. the Crocodiles, though living chiefly in 

 water, have recourse to stratagem rather than speed, for the 

 capture of their prey, it may not be unprofitable to examine 

 the mechanical contrivances, by which a reptile, most nearly 

 allied to the Monitor, was so constructed, as to possess the 

 power of moving in the sea, with sufficient velocity to over- 

 take and capture such large and powerful fishes, as from 

 the enormous size of its teeth and jaws, we may conclude 

 it was intended to devour. 



The head and teeth, (PI. 20.) point out the near relations 

 of this animal to the Monitors ; and the proportions main- 

 tained throughout all the other parts of the skeleton, warrant 

 the conclusion that this monstrous Monitor of the ancient 

 deep was five and twenty feet in length, although the longest 

 of its modern congeners does not exceed five feet. The 

 head here represented measures four feet in length, that 

 of the largest Monitor does not exceed five inches. The 

 most skilful Anatomist would be at a loss to devise a series 

 of modifications, by which a Monitor could be enlarged to 

 the length and bulk of a Grampus,f and at the same time be 

 fitted to move with strength and rapidity through the waters 

 of the sea; yet in the fossil before us, we shall find the 

 genuine characters of a Monitor maintained throughout the 



* Remains of the Mosasaurus have been discovered by Mr. Mantcll in 

 the upper chalk near Lewes, and by Dr. Morton in tlie green sand of 

 Virginia. 



t The Grampus is from 20 to 25 feet long, and very ferocious, feeding on 

 seals and porpoises as well as on other fishes. 



