JURA-TRIAS IN AMERICA. 



455 



Birds, they vary in size from those of a snipe to those of the great 

 Brontozoum, eighteen inches long, and with a stride of four feet (Fig. 



720). This huge hird, if bird it was, 

 must have been at least fourteen feet 

 high (Dana). Such a huge animal must 

 have been wingless, like the ostrich, etc., 



Fig. 717. 



Fig. 718. 



Fig. 719. 



Figs. 717-719.— Kepttle-T racks (after Hitchcock): 717. Otozoum Moodii: a, hind-foot, x &; b, 

 fore-foot, x T l 5 . 718. Giguntitheriuin caudatum, x ^. 719. Anomcepus minor, x £: a, hind- 

 foot; b, fore-foot. 



for its size is far beyond the limit with- 

 in which flight is possible. 



We have expressed a doubt as to 

 whether these tracks be those of birds 

 or reptiles. This is not so strange as 

 it may at first appear. These two class- 

 es are, indeed, now very widely sepa- 

 rated, but then they were very closely 

 allied. There were probably animals 

 then living which, even if we saw them, 

 might puzzle us to decide whether to 

 call them reptilian birds or bird-like 

 reptiles. These tivo classes were not yet 

 fairly disentangled and separated from 

 each other. 



We may easily imagine the circum- 

 stances under which these tracks were 

 formed. During the Jura-Trias period 



Fig. 720.— Track of Brontozoum gigan- 

 teum, x | (after Hitchcock). 



