iNVESflGATION OF FAUNA ANd FLOHA OF TRIAS OF BRITISH ISLES. 221 



also in 1 824. The former were found by Dr. Duncan and described four 

 years later in the paper referred to above. The latter, although found in 

 1824, were not recognised as footprints by Sir P. Grey Egerton ' till 1836, 

 and were described in 1838 in a paper read at the Geological Society's 

 meeting, December 5, and at the same meeting the prints from Storeton 

 were described.^ 



The footprints vary greatly both in size and form, the smallest noticed 

 being about one-eighth of an inch and the largest 15 inches in length. The 

 variation in form is not only caused by differences in the form of the foot 

 itself, but also by the conditions under which the tracks were made, such 

 as the consistence of the mud, the action of the animal, whether moving 

 rapidly or otherwise, and the inclination of the surface.'* 



The prints are generally preserved as casts on the under surface of the 

 overlying sandstone. The bed of marl on which the original prints were 

 made, being very thin and friable, is seldom fit for removal. Immediately 

 after a slab is lifted the perfect prints are often visible, but rapidly 

 become obliterated. At Corncockle Muir, however, the prints themselves 

 are frequently preserved. 



The bed of marl is often much broken up by desiccation cracks and 

 otherwise deformed in drying, which greatly interferes with the preserva- 

 tion of impressions, and casts of these cracks often form a network of 

 ridges on the overlying sandstone. 



The beds in which the prints were made appear to have resulted from 

 temporary accumulations of water, which, as they disappeared, left behind 

 the mud, on which were preserved tlie footprints of whatever animals 

 happened to cross it. In the loose sand which formed the general surface 

 of the country such records of their presence would not be preserved. 



There is no indication in the forms preserved that they were produced 

 by water-loving animals ; there is no more reason for supposing that the 

 mud attracted an unusual concourse of animals than that it merely 

 recoi'ded the presence of the usual inhabitants. 



There is every probability that the sand was usually deposited on the 

 mud by a^olian rather than by aqueous agency. The prints were often 

 made in a very thin layer of mud (occasionally so thin that it adhered to 

 the foot of the animal, leaving the underlying sand exposed), and this 

 thin layer in drying was broken up by shrinkage and divided into a 

 number of curved plates, the curved surfaces being perfectly reproduced 

 on the under surface of the layer of sandstone above. Had this mud 

 been again covei-ed with water it would have lost its curvature, and the 



' ' On two Casts of Impressions of the Hind Foot of a gigantic Clieirotherium from 

 the New Red Sandstone of Cheshire,' by Sir P. Grey Egerton, Proe. Geol. Sou., 

 vol. iii. p. 11. Read December 5, 1838. 



• ' An Account of the Cbeirotherium and other unknown Animals lately discovered 

 in the Quarries of Storeton Hill, in the Peninsula of Wirrall, between the Mersey and 

 the Dee,' Proc. Geol. Soc, vol. iii. p. 12. Read December 5, 1838. This appears to 

 have been a report by the Liverpool Natural History Society written by Mr. J. 

 Cunningham and submitted by the Geological Society in London. 



^ A letter from Professor Buckland, dated Oxford, December 12, 1827, quoted in 

 Dr. Duncan's paper referred to above, shows how fully the importance of studying the 

 effect of varying conditions on the prints left by recent animals was recognised by 

 earlier investigators. 



Professor T. McKenna Hughes in the Qiiarfi'vly Journal Geological Society, vol. s.]. 

 p. 178, pis. 7-11, has a paper on ' Some Tracks of Terrestrial and Freshwater Animals,' 

 which, though referring to the tracks of invertebrates, has an important bearing on 

 the present subject. 



