412 



MESOZOIC TIME. 



is the last period in which this old Paleozoic characteristic appeared. 

 Thus, as Agassiz first observed, the progress of the ages was marked 

 in the tails of the fishes. 



Amphibians and True Reptiles were very numerous, and various in 

 size. But, although fragments of the skeletons of several species have 

 been found, most of the species are known only from their foot- 

 Figs. 719-724. 



Fig. 719, Macropterna divaricans ( x Y G ) ; 720, Apatichnus bellus (xK)i 721, Anomoepus scambus, 

 fore-foot (X 3^); 721 a, hind foot of same; 722, Anisopus Deweyan us, fore foot (xK);722o, 

 hiDd foot of same; 723, A. gracilis, fore foot (X%); 723 a, hind foot of same ; 724. Otozoum 

 Moodii, fore foot ; 724 a, hind foot of same (both Xy^). 



prints, Figs. 719-730. Their fossil bones have been discovered in 

 Prince Edward's Island, Massachusetts, Connecticut, Pennsylvania, 

 and North Carolina. One of the most interesting localities is at Phoe- 

 nixville, Pa., where there is literally "a bone-bed," as described by 

 Wheatley. The footprints, like those referred to birds, are most nu- 

 merous in the Connecticut valley area. 



1. Amphibians, of the order of Labyrinthodonts, whose tracks are 

 four-toed or five-toed and often hand-shaped. The ordinary Laby- 

 rinthodonts were quadruped-like in locomotion, the fore-feet being ordi- 

 narily used in walking as well as the hind feet. Fig. 722 represents 

 the track of the fore-foot of one of the species, and 722 a, that of the 

 hind foot, both half the natural size; and Figs. 723, 723 a, are the 

 tracks of the fore and hind feet of another species, two thirds the 

 natural size. Several other kinds are figured by Hitchcock in his 

 memoir on the Footprints (Ichnology) of New England. 



2. True Reptiles existed of the following kinds : — 



1. Dinosaurs. — The Dinosaurs were to a large extent biped in 

 locomotion, like birds, seldom bringing their fore-feet to the ground. 



