240 



GEOLOGY. 



Fig. 139. 



to belong to another animal, whose remains, however, 

 had never been discovered. The name of Cheirotheri- 

 um was given to this supposed animal because the tracks 

 were so much like the print of a hand, the word being 

 derived from two Greek words, cheir, hand, and therion^ 

 beast. It is now pretty well ascertained that these 

 tracks were all made by the Labyrinthodon. This name 

 is given to this animal from the structure of its teeth. 

 In Fig. 140, at a, is a tooth half its natural size, and at b 



Fig. 140. 



is part of a transverse* section magnified twenty diame- 

 ters. You see that the turnings on this surface have a 

 labyrinthine arrangement, and hence the name given to 

 the animal. At c is one of these turnings very highly 

 magnified. 



346. Tracks. The tracks of Triassic animals have 

 been observed by geologists in various quarters, but most 

 largely by Professor Hitchcock, of this country, in the 

 red sandstones of the Connecticut River Valley, where 



