ERA OF THE NEW RED SANDSTONE. 53 



distance. These two animals, of which many varieties 

 have been discovered, constituting distinct species, are 

 supposed to have lived m 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. Thepterodactyle 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 ot 

 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 (sawia, chelonia, 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 

 ultra-tropical heat and frequent volcanic disturbances. 

 A.n estuary, cut off by an upthrow of trap, or a change ot 

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

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

 iecond 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 



