228 HISTORICAL PALEONTOLOGY. 



footprints as well as by their bones; and a question has arisen 

 whether the supposed footprints of birds which occur in the 

 Trias have not really been produced by Deinosaurs. This 

 leads us, therefore, to speak at the same time as to the evi- 

 dence which we have of the existence of the class of Birds 

 during the Triassic period. No actual bones of any bird have 

 as yet been detected in any Triassic deposit; but we have 

 tolerably clear evidence of their existence at this time in '- 1 *e 

 form of footprints. The impressions in question are found in 

 considerable numbers in certain red Sandstones of the age of 

 the Trias in the valley of the Connecticut River, in the United 

 States. They vary much in size, and have evidently been 

 produced by many different animals walking over long 

 stretches of estuarine mud and sand exposed at low water. 

 The footprints now under consideration form a double series 

 of single prints, and therefore, beyond all question, are the 

 tracks of a biped that is, of an animal which walked upon 



Fig. 155. Supposed footprint of a Bird, from the Triassic Sandstones of the Con- 

 necticut River. The slab shows also numerous "rain-prints." 



two legs. No living animals, save Man and the Birds, walk 

 habitually on two legs; and there is, therefore, a prima facie 

 presumption that the authors of these prints were Birds. 

 Moreover, each impression consists of the marks of three toes 

 turned forward (fig. 155), and therefore are precisely such as 

 might be produced by Wading or Cursorial Birds. Further, 

 the impressions of the toes show exactly the same numerical 



