202 Dr DUNCAN on the Footmarks of Quadrupeds 



sent casts similar to those now transmitted, besides a small spe- 

 cimen of the rock itself, containing one or two foot-prints), I 

 think it may be interesting to state the opinion with which his 

 politeness has favoured me as to three of the tracks. 



Concurring with Mr JAMESON, as he assures me he does, in 

 the belief that the rock is what is called the new red sandstone, 

 which is supposed to have been deposited at an era when it is 

 the received opinion that no quadrupeds existed on our earth of 

 a higher order than reptiles, he was induced to look to our pre- 

 sent crocodiles and tortoises as the species most nearly resembling 

 those whose footsteps have marked the stone. This led him to 

 make a rough experiment with some live tortoises which he has in 

 his possession, the result of which was to make him conjecture 

 that the impressions must rather belong to the tortoise than the 

 crocodile tribe. He did not, however, speak positively ; not 

 that he thought the prints too indistinct to enable him to form an 

 opinion, but because he had not sufficient time and opportunity 

 for examination *. As to the deep tracks occasioned, as I had sug- 



* Since the above was written, I have had the pleasure to receive a letter from 

 Professor BOCKLAND, containing the following account of his experiments : 



" Oxford, I2th Dec. 1827. 



" 1*2, I made a crocodile walk over soft pye-crust, and took impressions of his 

 feet, which shew decidedly that your sandstone foot-marks are not crocodiles. 



" &/, I made tortoises, of three distinct species, travel over pye-crust, and wet 

 sand and soft clay ; and the result is, I have little or no doubt that it is to animals 

 of this genus that your impressions on the new red sandstone must be referred, 

 though I cannot identify them with any of the living species on which I made my 

 experiments. The form of the footstep of a modern tortoise corresponds sufficiently 

 well, but the relative position of the impressions to each other does not entirely co- 

 incide, and this I attribute to the different pace at which the animal was proceeding; 

 for I found considerable variety in these positions as my tortoises moved more or less 

 rapidly ; and as most animals have three distinct kinds of impression for their three 

 paces of walk, trot, and gallop, so I conceive your wild tortoises of the red sandstone 



