152 STORY OF THE REPTILES 



land, on account of its weight. Another, with ordi- 

 nary feet, had a hill like that of a spoonhill or 

 " shoveler " duck, and fed only on more tender 

 aquatic plants, as is shown by its teeth (Fig. Y2). 

 Upon this the terrible Lidaps — the talon-toed flesh- 

 eater — is supposed to have fed. 



Fig. 72. — Didonias mirabilis x j\ (after Cope). 



If we glance at Fig. 73, on page 153, we may 

 note how birdlike these reptiles were in shape, yet 

 the resemblance was stronger still in structure. It is 

 not necessary, however, to believe that birds came 

 from these monsters; but there were some strong 

 bird ward tendencies at work then. On page 154 are 

 the cuts of some tracks made by these old three-toed 

 bipedal walkers (Fig. 74). 



One of the most peculiar of these giants has been 

 called the fin-backed lizard. It was aquatic, swim- 

 ming by a long flattened tail. The spines on the 

 upper side of the back-bone grew up into a great 

 high arch like a fin ; and these, quite likely, had 

 membranes over them or between them. On one of 

 these, found by Professor Cope, there were cross-arms 

 as on the mast of a ship. We can see no use for 



