I ii nix and Mammals 



nmners of birds should have appeared in the 

 Tri;is, and it is by no means impossible that 

 some of the tracks in the red sandstone of the 

 Connecticut Valley were actually made by such 

 early birds or bird-like reptiles. Probably no 

 paleontologist ever looks upon these tracks 

 without an inward longing for a knowledge of 

 the creatures that made them. 



Many forms, too, are needed to bridge over 

 the wide gap that now separates the birds of 

 the Jurassic period from those of the Creta- 

 ceous, for the differences between them are 

 greater than between the birds of the Creta- 

 ceous and the present. Instead of long tails 

 with feathers arranged in pairs on either side, 

 the Cretaceous species seem to have had the 

 fan-shaped tails of existing birds ; * instead of 

 three-clawed and separate fingers, the bones of 

 the hand were united and adapted to the sup- 

 port of feathers. Teeth, however, are still 

 retained, and the freedom from one another of 



* Hesperornis very likely had a tail intermediate in pattern be- 

 tween these two, and he was so drawn by Mr. Gleeson in Animals 

 of the Past. 



179 



