Robert Harkness, Esq., on Fossil Footprints. 261 



otlier creatures of a higher organised type occurred, and 

 that these fulfilled the objects, and occupied the places, of 

 such mammalia as now prevail ; — that along with the Lizards 

 and Batrachians inhabiting the triassic shore, birds which 

 probably represented the sandpipers of the present day ex- 

 isted, and found their food amongst the shallows and mud of 

 this ancient beach. 



The occurrence of ichnolites in the Potsdam sandstone, 

 the base of the American Silurians, goes a long way towards 

 overthrowing the opinions which have been entertained, that 

 in the older formations organic forms were of the lowest 

 types. And when we reflect that these formations are exclu- 

 sively of marine origin, the cause of the generally low deve- 

 lopment of the remains at once presents itself. In the case 

 of the footprints, these are not such as to ally the Cheloniae 

 which formed them with those which impressed the Variegated 

 sandstone. The impressions of the Potsdam sandstone have 

 relation rather to Emydia than to land-tortoises, and in 

 these impressions we have indications not only of an exalted 

 form of animal life, but likewise of one inhabiting either an 

 estuary or fresh water ; and from this circumstance we may 

 infer that the drainage water of the land found its way at 

 this early period to the sea, and as there was an estuary and 

 fresh water, so there must have been dry land, which had 

 probably its inhabitants, concerning which we are at present 

 in total ignorance. The ichnolites of the trias afford evi- 

 dence of an important character, so far as the creation and 

 existence of organic forms are concerned. In the low beds of 

 the Variegated sandstone, as they are developed in Dumfries- 

 shire, we have the impressions of several species of CheloniaB, 

 Sauriao, and Batrachiae, differing in their footprints, and conse- 

 quently in their nature, from those which have been found in 

 the higher beds of this formation at Weston Point, Cheshire. 

 At this locality, however, we meet with occasionally the im- 

 pression of a small tortoise, which appears to be allied to 

 one of the small impressions of Dumfriesshire. On the 

 whole there is still sufficient to shew that different types in- 

 liabited the shore here ; and as there are certain indications 

 tliat at Weston Point the sandstone occupies a higher posi- 



