found in Sandstone in Dumfriesshire, 203 



gested, by the sliding of the animal, he fully adopted my theory 

 of their origin. The track of the large animal I had not then 

 described to him ; and any account of it I am even now able to 

 give, is so vague as to lead to no certain conclusion. The only 

 thing yet discovered which can afford any idea of the nature of 

 the foot, is the ridge formerly mentioned as curling round the 

 animal's heels, on the surface of the under stratum, correspond- 

 ing to which, but a little above it, there is, in one instance, on 

 the surface of the upper layer, a depressed line of the shape 

 and dimensions marked below : 



a fact which contradicts the commonly received opinion of 

 geologists respecting the position of sandstone in its original 



age would move with more activity and speed, and leave more distant impressions, 

 from a more rapid and more equable style of march, than my dull torpid prisoners 

 on the present earth in this to them unnatural climate. 



" I found, also, that, on walking down hill on soft sand, my tortoise scooped out 

 long and somewhat oval cavities, like those of which you sent me a cast, leaving no 

 impressions of the toes or heel. Each foot successively floundered forwards to the 

 lowest point of the groove, producing the posterior part of the excavation, and was 

 then dragged out, producing a similar removal of the sand from the anterior part of 

 the groove in question. The difficulty is to explain why sand so soft did not sub- 

 side and obliterate the cavities, before or during the arrival of the next superincum- 

 bent bed of sand, which filled up and preserved these impressions. Elongated exca- 

 vations similar to those last spoken of are made by hares and other quadrupeds, in 

 moving over soft and half consolidated snow." 



In a subsequent letter of 17th March, Professor BUCKLAND, in relation to the 

 elongated and imperfect impressions, which Dr DUNCAN attributed to the dragging 

 of the animals as they were moving with difficulty down hill, observes, " The cause 

 of this variety of impressions I would interpret otherwise, and rather refer them to 



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