24 ICHNOGRAPHS OF THE 



(PI. 25, fig. 3), without (PI. 26, fig. 1), and sometimes the impress of the anterior 

 foot is partially or altogether obliterated by that of the posterior foot, and both 

 pairs of the feet fall in regular alternation. 



The type of animals indicated by these diminutive footprints may be referred 

 with probability to the saurian order of existing reptiles, for there is an intimate 

 analogy in the structural configuration of their feet. Plate 21 represents the 

 footprints of a living alligator, and by comparing them with those of Plate 24, 

 fig. 1, the points of resemblance will be seen to be very intimate. The pos- 

 terior feet in each Plate have the same number, form, and radiation of the 

 toes, and the three inner ones in both are pointed with claws ; and there are 

 also like impressions of the metatarsi. The form and radiation of the anterior 

 feet are also conformable ; and upon these analogies a portion of these quadrupedal 

 impressions will be assumed to indicate animals who were the archetypes of 

 certain existing saurian reptiles. 



The impressions upon Plate 29, which are very minute, indicate a different 

 tribe of quadrupedal animals. Their feet were widely separated, and the anterior 

 foot is planted considerably in advance of the posterior. 



The origin of the remaining quadrupedal footprints cannot be clearly inferred 

 upon any known existing analogies; and the interest created by an investigation 

 of them is in proportion to their obscurity and anomalous combinations. The 

 footprints upon Plates 31 to 34 inclusive, indicate animals whose powers of loco- 

 motion were diversified, and who approached more nearly to the mammalian type 

 than any other form of the sandstone footprints. It will be seen in the analysis 

 of these remarkable impressions, that the feet partake of the characteristics of 

 both birds and reptiles ; that is, the posterior foot conforms strictly to the ornithic 

 impressions, and the anterior to the reptilian. In Plates 33 and 34 the larger 

 feet are, in respect to the phalangeal arrangement, the heel and nails, conformable 

 to the ornithic impressions ; while the lesser, or anterior footprints, are strictly 

 upon the reptilian type. In this style of quadrupedal footprints, the same alter- 

 nation of the feet occurs as in the foregoing saurian examples: the anterior 

 and posterior feet fall upon the surface nearly together; and, if the posterior foot- 

 print be considered independently of its companion, it will without hesitation be 

 pronounced to be ornithic in its character and indications. 



In Plates 31 and 32 the same type of feet prevails, but their positions and 

 relations are materially different, as if the creature had assumed the jumping 



