SPECIAL GEOLOGY. 389 



The fish here depicted has the mouth open, the gills and 

 the fins extended, while the body is uncompressed ; from 

 which it is inferred that the creature must have been living, 

 moving, and breathing, when it was surrounded by the chalk. 





FIG. 273. Osmeroides Muntellii. 



THE MOSASAURUS. The chalk of Kent and Sussex have 

 likewise afforded teeth, a jaw, and vertebra, of the mosa- 

 saurus, or lizard of the Meuse, a reptile which, excited very 

 considerable interest at the period of its discovery. It was 

 a marine saurian, intermediate between the monitor and 

 iguana; it is supposed to have been twenty-five feet in 

 length, and to have possessed a tail, which became flat, like 

 an oar, at some distance from the body, and formed a 

 powerful instrument of propulsion-. 



In the greensand of the vicinity of Hythe, the remains of 

 a reptile of colossal size have been discovered, which, from 

 the teeth exhibiting peculiar fold-like markings, has been 

 described under the name of the PotyptycJiodon* 



parvenu a les detacher, entitlement, de la roche dans laquelle ils se trouvaient; 

 ou du moins, a les produire en relief, en detachant toutes les matieres solidcs 

 qui recouvraient les parties les mieux conservees de 1'anicnal." 



The late F. Dixon, Esq., of Worthing, has formed a splendid collection of 

 the fossils of the chalk, comprising many rare and unique specimens, among 

 which are examples of the Hijtpurites and Sphcerulites, which, though not 

 unfrequent in the cretaceous rocks of the Pyrenees and other parts of the Con- 

 tinent, are most rare in the English chalk. These form the subject of his 

 beautiful monograph on the Geology and Fossils of the Tertiary and Creta- 

 ceous Formations of Sussex. 



* Now in the British Museum. See Proceedings of the Geological 

 Society, part iii., p. 449. 



