Mr Mantell on the Geol>jff'icul Jge (rf' Reptiles. 185 



clearly been formed in the bed of" a river ; while those of Stones- 

 field, which contain a somewhat similar association of fossils, 

 have as evidently been deposited by a current which ran into the 

 ocean of the oolite, and carried with it remains of tei'restrial and 

 fresh-water animals, the shells in tiie last named strata being, as 

 before remarked, marine, and precisely similar to those of the 

 deposites above and below them ; while the shells of the Has- 

 tings' beds are decidedly fluviatile or lacustral. Besides the re- 

 mains of the reptiles above mentioned, teeth and bones of other 

 gigantic oviparous quadrupeds have been found, but the charac- 

 ters and relations of the latter have not yet been accurately de- 

 termined. 



In the extensive marine formation, the chalk, which covers 

 the Hastings' beds, reptiles are less numerous, and the Megalo- 

 saurus, Iguanodon, and other herbivorous genera, disappear al- 

 together ; no traces of their existence occurring after the last 

 named strata were deposited. At the epoch of the chalk for- 

 mation, the Ichthyosaurus, and one or more species of crocodile, 

 and marine turtles, existed ; and another extraordinary reptile, 

 the Mososaurus (lizard of the Meuse), or fossil animal of Maes- 

 tricht, first appears. This creature, so celebrated in Orycto- 

 logy since the first discovery of its head and jaws by Hoffman, 

 attained the size of the crocodile, and held an intermediate place 

 between the Monitors and Iguanas. It appears to have been 

 aquatic, swimming in the manner of a crocodile, and moving its 

 vast tail from side to side as an oar. With the chalk, the 

 " age of reptiles" may be said to terminate — the greater part of 

 the genera above noticed appears to have become extinct during 

 the changes which took place on the surface of the earth at that 

 period ; the crocodiles, turtles, &c. alone survived, a new order 

 of things commenced, and in the tertiary formations which suc- 

 ceeded, we perceive an approach to the modern condition of the 

 earth. 



