^{page 194 note *} In his Mineralogical Survey of Dumfriesshire.

^{page 195 note *} The accompanying engraving (Plate VIII.) is taken from the cast No. 1, and is on a reduced scale.

^{page 196 note *} It is not meant that the quadruped has actually been in this position; for tht hind-foot would of course be moved forward before the fore-foot was lifted.

^{page 198 note *} That is, when the fore-foot was advanced, and the hind-foot thrown back in the act of moving forward.

^{page 200 note *} Specimen marked A.

^{page 201 note *} Specimen marked B, on which there is also the track of a small animal ascending.

^{page 202 note *} Since the above was written, I have had the pleasure to receive a letter from Professor Buckland, containing the following account of his experiments: “Oxford, 12th Dec. 1827. “1st, 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. “2d, 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 coincide, 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 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 subside and obliterate the cavities, before or during the arrival of the next superincumbent bed of sand, which filled up and preserved these impressions. Elongated excavations 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 the more than usual soft condition of the sand at the time and place where these imperfect marks were made. Marks exactly like those made by my living tortoises, on sand that was wetted too much for a sound impression, viz. holes into which the foot had sunk so deep that it could not be lifted out and moved forward by the advancing animal without displacing by its toes a quantity of the sand that was in front of the line of motion of each foot, and the result being a series of scoopings such as the track of a hare or rabbit exhibits in soft and deep snow. If this idea be correct, the impressions may have been made on horizontal beds of soft sand, ere they had received the high degree of inclination they now possess. Thus the problem will be relieved of some portion of its difficulty, namely, that which attends the hypothesis of all the impressions having been made on the sand-beds whilst inclined at the same angle they exhibit at present.”

^{page 204 note *} The casts and specimens here alluded to are deposited in the Museum of the Society, and may be inspected by application to any of its members.