288 HISTORICAL PALEONTOLOGY. 



from the type-genus Mosasaurus. The first species of Mosa- 

 saurus known to science was the M. Camperi (fig. 210), the 

 skull of which six feet in length was discovered in 1780 in 

 the Maestricht Chalk at Maestricht. As this town stands on 

 the river Meuse, the name of Mosasaurus (" Lizard of the 

 Meuse") was applied to this immense Reptile. Of late years 

 the remains of a large number of Reptiles more or less closely 

 related to Mosasaurus, or absolutely belonging to it have been 

 discovered in the Cretaceous deposits of North America, and 

 have been described by Professors Cope and Marsh. All 

 the known forms of this group appear to have been of large 

 size one of them, Mosasaurus princeps, attaining the length of 

 seventy-five or eighty feet, and thus rivalling the largest of ex- 

 isting Whales in its dimensions. The teeth in the " Mosa- 

 sauroids " are long, pointed, and slightly curved ; and instead 

 of being sunk in distinct sockets, they are firmly amalgamated 

 with the jaws, as in modern Lizards. The palate also carried 

 teeth, and the lower jaw was so constructed as to allow of the 

 mouth being opened to an immense width, somewhat as in the 

 living Serpents. The body was long and snake-like, with a 

 very long tail, which is laterally compressed, and must have 

 served as a powerful swimming-apparatus. In addition to this, 

 both pairs of limbs have the bones connecting them with the 

 trunk greatly shortened; whilst the digits were enclosed in the 

 integuments, and constituted paddles, closely resembling (in 

 structure the "flippers" of Whales and Dolphins. The neck 

 is sometimes moderately long, but oftener very short, as the 

 great size and weight of the head would have led one to antic- 

 ipate. Bony plates seem in some species to have formed an 

 at any rate partial covering to the skin; but it is not certain 

 that these integumentary appendages were present in all. Up- 

 on the whole, there can be no doubt but that the Mosasauroid 

 Reptiles the true " Sea-serpents " of the Cretaceous period- 

 were essentially aquatic in their habits, frequenting the sea, 

 and only occasionally coming to the land. 



The " Mosasauroids " have generally been regarded as a 

 greatly modified group of the Lizards (Lacertilia). Whether 

 this reference be correct or not and recent investigations 

 render it dubious the Cretaceous rocks have yielded the 

 remains of small Lizards not widely removed from existing 



