TRIASSIC PERIOD. 



415 



Fig. 730. 



Birds. - — The evidence with regard to the existence of Birds at this 

 period has been shaken by the discovery of the three-toed reptile- 

 tracks ; and it is very probable, as was early suspected, that all the 

 supposed bird-tracks will turn cut to be Reptilian. Still, it is possible 

 that there were Birds as well as 

 Reptiles, for the existence of birds 

 in the Jurassic era in Europe has 

 been proved by the discovery of 

 specimens (p. 447). 



The tracks referred to Birds, are 

 very various in kind and size. 

 Fig. 730 (from Hitchcock), repre- 

 sents a large slab, with its lines 

 of tracks, showing that a num- 

 ber of these three-toed animals (a, 

 b, c) and at least one Amphibian 

 (d) passed over the muddy surface 

 during the same day, or before the 

 tides or freshets made new depo- 

 sitions of detritus : the tracks, «, a, 

 are enlarged views of b, and still 

 are only one tenth of the natural 

 size. Three-toed tracks not yet 

 proved by impressions of fore-feet to be those of Reptiles, have been 

 found not only at various places in the Connecticut valley, but also in 

 New Jersey above Trenton, and in Pennsylvania near Easton, and at 

 the Phcenixville tunnel on the Schuylkill. 



Of all the various kinds of tracks found in the Connecticut val- 

 ley, the collections of Amherst College, made chiefly by Professor 

 Edward Hitchcock, and also that of Yale College, contain each 

 several thousands of specimens ; a fact that gives some idea of the 

 abundance of life on the continent in Triassic time. Other estua- 

 ries and valleys besides those now occupied by Triassic beds, were 

 probably equally populous. Twenty-one consecutive tracks of the 

 Otozoum were exposed to view in 1874, at one of the Portland quar- 

 ries. 



Mammals. — The only Mammal 

 thus far discovered in the Ameri- 

 can rocks was made known by 

 Professor Emmons. The specimens 

 are two jaw-bones (Fig. 731), found 

 in North Carolina. According to D^matherium syivestre. 



Professor Owen, they belonged to an Insectivorous (insect-eating) 



Slab of sandstone, with tracks of 

 Birds (?) and Reptiles (Xjj). 



Fig. 731. 



