222 HISTORICAL PALEONTOLOGY. 



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

 tolerably clear evidence of their existence at this time in the 

 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 

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



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

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



might be produced by Wading or Cursorial Birds. Further, 

 the impressions of the toes show exactly the same numerical 

 progression in the number of the joints as is observable in 

 living Birds — that is to say, the innermost of the three toes 

 consists of three joints, the middle one of four, and the outer 

 one of five joints. Taking this evidence collectively, it would 

 have seemed, until lately, quite certain that these tracks could 

 only have been formed by Birds. It has, however, been 

 shown that the Deinosaurian Reptiles possess, in some cases 

 at any rate, some singularly bird -like characters, amongst 



