48 ICHNOGRAPHS OF THE 



PLATE XXX. 



Fig. 1. The impressions of this figure, as well as those of the next mentioned, 

 were supposed by Dr. Deane to have been made by biped tailed animals. They rep- 

 resent but a portion of those upon the original stone, beyond which is a succession 

 of twelve or more footprints. Besides these and the impression made by the tail, the 

 surface is covered over with the markings of rain-drops; and, what is peculiar, the tracks 

 of little streamlets made by a combination of drops. No attempt, of course, was made 

 to represent these last on the drawing, but they render the slab exceedingly interesting. 



Dr. Hitchcock has described the species as the Selenichnus breviusculus. He 

 judges the animal to have been a Batrachian. 



The stone is in possession of Roswell Field. 



Fig. 2. This drawing represents the track of an animal of similar character to the 

 last mentioned, and may be found described by Dr. Hitchcock under the name of Selen- 

 ichnus falcatus. The impressions of both Figures 1 and 2 of this Plate are of tracks 

 made in soft mud, and it is impossible to determine by them, with certainty, whether 

 they were made by a biped or quadruped. 



The quadrupedal impressions delineated upon Plates 31, 32, 33, 34, 35, and 

 36 are distinctly different from those already described, and constitute a peculiar 

 group. The posterior foot is ornithic in type, that is, it is tridactylous, and 

 conforms in all respects to that of birds. The anterior foot is reptilian in its 

 form and character. The impressions all agree in this particular, but they differ 

 in respect to the relative positions in which they occur, and indicate distinct 

 modes of locomotion by the animals making them. In Plates 31 and 32 the 

 movement is by leaping, in Plates 33 and 34 it is by walking, as in the higher 

 grades of reptiles, and in Plates 35 and 36 by the crawling reptiles. These 

 impressions will repay a careful analysis. 



PLATES XXXI. AND XXXII. 



The subjects illustrated by these Plates are among the most interesting, and 

 at the same time the most perplexing to comprehend, of all the sandstone vestiges. 

 The footprints are those of quadrupedal reptiles, of a distinct order, having no 



