52 



ERA OF THE NEW RED SANDSTONE 



tysomus, &c., have been applied, vanish, and henceforth 



appear no more. 



The third group, chiefly sandstones, variously colored 

 according to the anfbunt and nature of the metallic oxide 

 infused into them shows a recurrence of agitation, and a 

 consequent diminution of the amount of animal life. In 

 the upper part, however, of this group, there are abundant 

 symptoms of a revival of proper conditions for such life. 

 There are marl beds, the origin of which substance in 

 decomposed shells is obvious ; and in Germany, though 

 not in England, here occurs the muschelkalk, containing 

 numerous organic remains (generally different from those 

 of the magnesian limestone,) and noted for the specimens 

 of land animals, which it is the first to present in any con- 

 siderable abundance to our notice. 



These animals are of the vertebrate sub-kingdom, but 

 of its lowest class next after fishes — namely, reptiles — a 

 portion of the terrestrial tribes whose imperfect respira- 

 tory system, perhaps, fitted them for enduring an atmos- 

 phere not yet quite suitable for birds or mammifers.* 

 The specimens found in the muschelkalk are allied to the 

 crocodile an/1 lizard tribes of the present day, but in the 

 latter instance are upon a scale of magnitude as much su- 

 perior to present forms as the lepidodendron of the coal 

 era was superior to the dwarf club-mosses of our time. 

 These saurians also combine some peculiarities of struc- 

 ture of a most extraordinary character. 



The animal to which the name ichthyosaurus has been 

 given, was as long as a young whale, and it was fitted for 

 living in the water, though breathing the atmosphere. It 

 had the vertebral column and general bodily form of a fish, 

 but to that were added the head and breast-bone of a li- 

 zard, and the paddles of the whale tribes. The beak, 

 moreover, was that of a porpoise, and the teeth were 

 those of a crocodile. It must have been a most destructive 

 creature to the fish of those early seas. 



The plesiosaurus was of similar bulk, with a turtle-like 

 body and paddles, showing that the sea was its element, 

 but with a long serpent-like neck, terminating in a sau- 

 rian head, calculated to reach prey at a considerable 

 * The immediate effects of the slow respiration of the reptilia, 

 are, a low temperature in their bodies, and a slow consumption ol 

 food. Requiring little oxygen, they could have existed in an at- 

 mosphere containing a less proportion of that gas to carbonic acid 

 gas than what now obtains. 



