412 



MESOZOIC TIME. 



is the last jieriod 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. 



The Reptiles were very diversified in form and size. But, although 

 fragments of the skeletons of several sjaecies have been found, a much 

 larger number are known only from their footprints, Figs. 719-730. 



Figs. 719-724. 



Tig. 719, Macropterna divaricans ( xy e ) ; 720, Apatichnus bellus (XX) ; 721, Anomoepus scanibus, 

 fore-foot (y.%)', 721 a, hind foot of same; 722, Anisopus Deweyanus, forefoot (XK); 722 a, 

 hind 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 X -At)- 



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 Phcenixville, Pa., where there is 

 literally " a bone-bed," as described by Wheatley. The footprints 

 like those referred to birds are most numerous in the Connecticut val- 

 ley area. 



The reptiles were of the following kinds : — 



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

 four-toed or five-toed and often hand-shaped. There were two kinds of 

 them. One, the ordinary Labyrinthodonts, which were quadruped-like 

 in locomotion, the fore-feet being ordinarily used in walking; the other, 

 virtually bipeds, the fore-feet or hands seldom coming to the ground. 

 Figs. 722 represents the track of the forefoot of one of the former, 

 and 722 a, that of the hind foot, both half the natural size. Figs. 723, 

 723 a, are the tracks of the fore and hind feet of another species, two- 

 thirds the natural size. Of the bipeds, Figs. 719 represent, of re- 

 duced size, three consecutive tracks — right foot, left foot, right foot 

 — of one kind, the length of each about three inches. Fig. 724 a 



