CONNECTICUT RIVER SANDSTONE. 23 



In these typical features of the ornithic footprints, it will be seen that there 

 is an exact agreement with the footprints of living tridactylous birds, that appar- 

 ently establishes the cognate relations of the extinct and living races. The 

 same alternation and consecutive series of steps distinguish the movements of 

 each type of birds; and, in all essential particulars, a mutual agreement exists, 

 that appears to connect them by indubitable analogies. Until a recent period 

 no fact has ever appeared to disturb the ornithic theory of a portion of the 

 footprints; but late discoveries disclose the singular fact, that other contempo- 

 raneous animals that were quadrupedal possessed a similar organization of the 

 posterior foot (Pis. 33 and 34). But, from the accurate comparison of the 

 ornithoid impressions with those of existing birds, it is proper to consider them 

 to be analogous, although future discoveries may prove the grounds of this belief 

 to be fallacious. 



The reptilian footprints, that are supposed to indicate animals of saurian type, 

 are distinguished for inferior magnitude and for the disproportion of the anterior 

 and posterior feet, the latter being several times greater than the former (Pis. 

 23 to 26 incl.). This characteristic feature is indeed common to all varieties 

 of quadrupedal footprints. As a general rule each foot consists of four toes ; 

 but the anterior foot sometimes has five (PL 25, fig. 1). The toes are com- 

 paratively stout, and the feet massive. In some examples the toes are in contact 

 (PL 23), but they usually radiate from a common centre (PL 24). In other 

 examples, those of the posterior feet are parallel, while those of the anterior feet 

 radiate (PL 23). With <one exception (PL 24, fig. 2), each foot points obliquely 

 outward ; and the divergence of the anterior foot is sometimes so great as to 

 point directly outward (PL 23). As an invariable rule the ornithic footprint inclines 

 inward, and the inclination is in direct proportion to the length of stride. When 

 the step is long, the convergence of the foot is slight; but when it is short, 

 the foot points prominently inward. The central toe, in ornithoid footprints, points 

 with precision to the succeeding footprint. The convergence or divergence of 

 the footprints, then, indicates the class to which the animals making them belonged. 

 It rarely happens that the phalangeal divisions of the toes, in the saurian types, 

 can be determined, although it is sometimes the case ; yet the symmetrical pro- 

 portions of their feet are usually well preserved. In walking, the posterior foot 

 falls upon the ground near the place of the anterior foot, usually a little distance 

 behind (PL 24, fig. 2), within and behind (PL 24, fig. 1), before and without 



