FOOT-STEPS IN RED SANDSTONE. SUCCESSION OF STRATA. 167 



tinct impressions of a similar kind. There can be scarcely a doubt, 

 that they were the real foot-marks of a digitated animal having short 

 toes and claws, and the foot broad in proportion to its length. The 

 breadth of the foot is above one inch. The part of the sandstone in 

 Mr. Murray's possession, appeared to be composed principally of gran- 

 ular fragments of reddish quartz rock and felspar, with spots of chlo- 

 rite or hornblende. As remains of reptiles have been found in the 

 zetchstein or magnesian limestone on the Continent, which is as an- 

 cient as the new red sandstone, may not this animal have been a rep- 

 tile allied to the tortoise ? 



Since the publication of the third edition of this work, Professor 

 Buckland has, I believe, ascertained that the foot-marks are similar 

 to the foot-marks which some species of tortoise make in sand. 



Before concluding the account of the red sandstone, it may be 

 proper to repeat, that in a formation of such complexity, it is often 

 difficult to determine to which part of the series any particular bed 

 belongs, unless its situation be indicated by some of the limestone 

 beds, which sometimes occur in different parts of it. Thus, in De- 

 vonshire, the porphyrilic beds and conglomerates may belong to the 

 lowest, or to the middle series of sandstones : their position, with 

 respect to the rocks on which they rest unconformably, does not as- 

 sist in the discovery. In Yorkshire, the very lowest series rest on 

 coal measures, as stated by Professor Sedgwick, in his masterly and 

 luminous description of the geological relations of the magnesian 

 limestone, from Northumberland to Nottinghamshire. At Cham- 

 wood Forest, the uppermost series rests on ancient granitic and slate 

 rocks, as represented in Plate III. fig. 4. «, a. In the lowest beds, 

 resting on the slate, I observed indications of their mode of forma- 

 tion, which I intend afterwards to describe. Professor Sedgwick 

 first ascertained the true relations of the lower sandstone ; but, twen- 

 ty years before, in the first edition of this work, (1813, p. 270.) I 

 gave a brief account of the Pontefract sand rock, as the last of the 

 rock formations over coal, in a description of a section from the 

 Yorkshire to the Lancashire coast : — " The magnesian limestone is 

 succeeded by yellow siliceous sandstone, on which the town of Pon- 

 tefract is built. We may consider this as the boundary of the low 

 calcareous district: proceeding in a direction to Wakefield, we soon 

 come upon the argillaceous coal strata of the middle district." 



Professor Sedgwick arranges the red sandstone and magnesian 

 limestone in an ascending series. 



1. Lower red sandstone, yellow and red. 



2. Marl slate and compact limestone. 



2 a. Compact and shelly limestone, and variegated marls. 



3. Yellow magnesian limestone. 



4. Lower red marl and gypsum. 



5. Upper thin bedded limestone. 



6. Upper red sandstone. 



7. Upper red marl and gypsum. 



