DISTRIBUTION OF BIRDS. 389 



Secondly, The impressions are mostly tridactylous that is to 

 say, formed by an animal with three toes on each foot, as is 

 the case in many Waders and most Cursorial Birds. 



Fig. 331. Footprint supposed to belong to a Bird. Triassic Sandstones 

 of Connecticut. 



Thirdly, The impressions of the toes show the same numeri- 

 cal progression in the number of phalanges as exists in living 

 birds that is to say, the innermost of the anterior toes has 

 three phalanges, the middle one has four, and the outermost 

 toe has five phalanges. 



Taking this evidence collectively, it would have seemed, till 

 lately, tolerably certain that these impressions were formed by 

 Birds. We must not, however, lose sight of the possibility 

 that these impressions may have been formed by Reptiles 

 more bird-like in their characters than any of the living forms 

 with which we are acquainted. The recent researches of 

 Huxley, Cope, and others, go to show that the Deinosaurian 

 Reptiles possessed the power of walking, temporarily or per- 

 manently, on the hind-legs, and many curious affinities to the 

 true Birds have been pointed out. It is therefore by no means 

 impossible that these footprints of the Connecticut valley are 

 truly Reptilian.* 



The size and other characters of the above-mentioned im- 

 pressions vary much, and they have certainly been produced 



* The occurrence of many^/wr-fo^/impressions in these same Sandstones, 

 and the further discovery of the bones of Deinosaurian Reptiles in the same 

 beds, have rendered the Reptilian nature of many of these footprints almost 

 certain ; but some may possibly have been formed by Birds. 



