FAUNA OF THE CARBONIFEROUS AGE. 



401 



" We thus learn," says Dana, " that there existed in the region about 

 Pottsville, at that time, a mud-flat on the border of a body of water ; 

 that the flat was swept by wavelets, leaving ripple-marks ; that the rip- 

 ples were still fresh when a large amphibian walked across the place ; 

 that a brief show- 

 er of rain follow- 

 ed, dotting with 

 its drops the half- 

 dried mud ; that 

 the waters again 

 flowed over the 

 flat, making new 

 deposits of detri- 

 tus, and so buried 

 the records." This 

 the earliest 



is 



known land -ver- 

 tebrate. 



Similar tracks 

 have also been 

 found in the Coal- 

 measures of Penn- 

 sylvania, on a slab 

 affected with sun- 

 cracks (Fig. 578)- 

 The reptile had 

 evidently walked 

 on the cracked 

 and half - dried 

 mud at low tide. 

 Tracks have also 

 been found in the 

 Coal-measures of 

 Illinois, Indiana, 



Kansas, and Nova Scotia, and in the latter region beautiful specimens 

 of rain-prints (Fig. 577). 



There can be little doubt that the reptiles making the tracks men- 

 tioned above were Labyrinthodonts. 



2. Dendrerpeton. — In the Coal-measures of Nova Scotia have been 

 found quite a number of small reptiles, belonging to several genera. 

 Among these one is especially interesting, on account of the conditions 

 under which it seems to have been preserved. It is called the Den- 

 drerpeton — tree-reptile (Fig. 579), because it was found by Dawson and 

 Lyell in sand-stone, filling the hollow stump of a Sigillaria (Fig. 580), 

 26 



Fig. 578. 



-S'ab of Sandstone with Keptilian Footprints, from Coal-meas- 

 ures of Pennsylvania; x \. 



