THE CRETACEOUS PERIOD. 



279 



which it very closely resembles, appears to have walked upon 

 its hind-legs, the fore-limbs being disproportionately small. 



Another remarkable group of Reptiles, exclusively confined 

 to the Cretaceous series, is that of the Mosasauroids, so called 

 from the type-genus Mosasaurns, The first species of Mosa- 

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



Fig. 210. Skull of Mosasaurus Camperi, greatly reduced Maastricht Chalk. 



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

 the Maestricht Chalk at Maastricht. 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 \\\&m,Afosasaurusprinceps, 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 oairs of limbs have the bones connecting them with the 



