156 PALEONTOLOGY 



The best-defined footprints in the new red sandstone 

 quarries at Stourton, on the Cheshire coast, are found where 

 strata of sandstone are separated by a thin layer of argil- 

 laceous stone, which, when exposed, soon breaks up and 

 crumbles away. This layer has, however, received the im- 

 pressions when it was plastic, and the superincumbent deposit 

 of sandstone retains those impressions in relief upon its under 

 surface. The observations which have just been recorded, of 

 the circumstances that produce an interposition of a thin layer 

 of claystone between thicker beds of sandstone, and which 

 circumstances the writer has witnessed in the Bay of More- 

 combe, explain the formation and the preservation of the best 

 " ichnites" of the labyrinthodont and other reptiles in the new 

 red sandstone of Stourton. 



There is a third condition under which impressions, and 

 casts of impressions, on a sandy beach may be preserved. On 

 a dry windy day clouds of fine sand are drifted along the 

 surface exposed at low-water, are spread lightly over all 

 its little inequalities, and fill up every impression that may 

 have been made on it since it was left bare by the retreating- 

 waves. On the return of the tide, the fine sand filling the 

 impressions is moistened, and more wet fine sand is added 

 to it ; and a cast is thus fixed in the moulds, to be more and 

 more firmly fixed by each deposition from successive tidal 

 waves. 



Thus may be witnessed the actual conditions and the cir- 

 cumstances daily occurring that tend to preserve footprints 

 and other impressions made on the sea-shore, and which have 

 operated in past time to similarly preserve the impressions 

 then made on tracts alternately exposed and covered by the 

 tidal wave. The merit of having first discerned the nature 

 and cause of the numerous small hemispheric pits and tuber- 

 cular casts in relief on the surface of certain sandstone slabs, 

 is due to John Cunningham, Esq., F.G.S., architect, of Liver- 



