AGES OF NATURE. 



197 



Hitchcock, in the red sandstone of the Connecticut, have 

 made us acquainted with a great number of birds' tracks 



a Fig. 158. b c 



(Fig. 157, #, &), belonging to this epoch, for the most part in- 

 dicating birds of gigantic size. These impressions, which he 

 has designated under the name of Ornithichnites, are some 

 of them eighteen inches in length, and five feet apart, far 

 exceeding in size the tracks of the largest ostrich. Other 

 tracks, of a very peculiar shape, have been found in the red 

 sandstone of Germany and in Pennsylvania. They were 

 probably made by Reptiles, which have been called Chei- 

 rotherium, from the resemblance of the track to a hand (c). 

 The Mollusks, Articulates, and Radiates of this period, 

 approach to the fauna of the succeeding period. 



484. The fauna of the Oolitic formation is remarkable for 

 the great number of gigantic Reptiles which it contains. In 



a 



this formation we find those enormous Amphibia, known 

 under the name Ichthyosaurus, Plesiosaurus, Megalosaurus, 

 and Iguanodon. The first, in particular, the Icthyosaurus 

 (Fig. 159, a), greatly abounded on the coast of the conti- 

 nents of that period, and their skeletons are so well pre- 

 served, that we are enabled to study even the minutest 

 details of their structure, which differs essentially from that 

 of the Reptiles of the present day. In some respects they 

 form an intermediate link between the Fishes and Mammals, 



