OF PLANTS AND ANIMALS. 175 



carboniferous rocks have been included within the geologi- 

 cal formations of this period by some geologists, because 

 they contain the remains of the first land animals ; whereas 

 in the paleozoic age, the animals were altogether marine, 

 breathing by gills. Reptiles, however, are not found in 

 the coal measures, and do not make their appearance until 

 about the time of the deposition of the New Red Sandstone, 

 which took place immediately after the formation of the 

 carboniferous rocks. The tracks of a gigantic Batrachian 

 animal, a creature allied to the frog, have been left on the 

 New Red Sandstone of Pennsylvania and Germany ; enor- 

 mous aquatic birds have also left the impression of their 

 footsteps on the same rocks in Connecticut. 



The reptiles seem to have attained their maximum de- 

 velopment during the Oolitic period. We find in this for- 

 mation those enormous amphibia known by the names 

 Ichthyosaurus, Plesiosaurus, Megalosaurus and Iguanodon, 

 animals somewhat allied to the lizard and crocodile in 

 structure. But the most wonderful relic of the age of 

 reptiles, is the Pterodactylus, which resembled a gigantic 

 bat, and is thought to have been capable of flying. The 

 trilobites are now extinct ; but in the upper stages of the 

 Oolitic, we meet with tortoises and also the impressions of 

 several families of insects, among which dragon flies and 

 beetles are conspicuous. 



All the invertebrated animals, including the mollusca, 

 the articulata, and the radiata, are largely represented. The 

 peculiar forms of the paleozoic age have nearly all disap- 

 peared, and are replaced by creatures whose organization 

 is adapted to the new conditions. Of the brachiopod mol- 

 luscs, only one type is abundant, that of the Terebratula. 

 The G-asteropods display a great variety of species, and also 

 the Cephalopods, among which the Ammonites are the 



