ERA OF THE NEW RED SANDSTONE. 



53 



^stance. These two animals, of which many varieties 

 have been discovered, constituting distinct species, are 

 supposed to have lived in the shallow borders of the seas 

 of this and suosequent formations, devouring immense 

 quantities of the finny tribes. It was at first thought that 

 no creatures approaching them in character now inhabit 

 the earth ; but latterly Mr. Darwin has discovered in the 

 reptile-peopled Galapagos Islands, in the South Sea 9 a ma- 

 rine saurian from three to four feet long. 



The megalosaurus was an enormous lizard — a land 

 creature, also carnivorous. The pterodactyl e was another 

 lizard, but furnished with wings to pursue its prey in the 

 air, and varying in size between a cormorant and a snipe. 

 Crocodiles abounded, and some of these were herbivorous. 

 Such was the iguanodon, a creature of the character of 

 the inguana of the Ganges, but reaching a hundred feet in 

 length, or twenty times that of its modern representative. 



There were also numerous tortoises, some of them reach- 

 ing a great size ; and Professor Owen has found in War- 

 wickshire some remains of an animal of the batrachian 

 order,* to which, from the pecular form of the teeth, he 

 has given the name of labyrinthidon. Thus, three of 

 Cuvier's four orders of reptilia (sauria, thelonia, and ba- 

 trachia) are represented in this formation, the serpent 

 order (ophidia) being alone wanting 



The variegated marl beds which constitute the upper- 

 most group of the formation, present two additional genera 

 •of huge saurians — the phytosaurus and mastodonsaurus. 



It is in the upper beds of the red sandstone that beds 

 of salt first occur. These are sometimes of such thick- 

 ness, that the mine from which the material has been ex- 

 cavated looks like a lofty church. We see in the presen* 

 world no circumstances calculated to produce the forma- 

 tion of a bed of rock salt- yet it is not difficult to under- 

 stand how much strata were formed in an age marked by 

 *iltr a- tropical heat and frequent volcanic disturbances. 

 An estuary, cut off by an upthrow of trap, or a change of 

 level, and left to dry up under the heat of the sun, would 

 quickly beeome the bed of a dense layer of rock salt. A 

 second shift of level, or some other volcanic disturbance, 

 connecting it again with the sea, would expose this stra- 

 tum to being covered over with a layer of sand or mud, 

 destined in time to form the next stratum of rock above it 

 * The order to which frogs and toads belong 



