146 Physical Geography. 



found footprints, apparently of Labyrinthodonts, at 

 Brownrigg, in Plumpton, and near Penrith ; and many 

 years ago numerous footprints were described by the 

 late Sir William Jardine, which were found on the sur- 

 faces of beds of sandstone in Corncockle Moor and in 

 other parts of Dumfriesshire. All of these footprints 

 clearly indicate that the animals were occasionally 

 accustomed to walk on bare damp surfaces, which were 

 afterwards dried by the heat of the sun, before the 

 flooded waters overspread them with new layers of 

 sediment in a manner such as now takes place during 

 variations of the seasons in many modern salt lakes. 

 Pseudomorphs of crystals of salt in the Permian beds 

 of the Vale of Eden, and deposits of gypsum and per- 

 oxide of iron, help to this conclusion, together with 

 the occurrence of sun-cracks or rain-pittings impressed 

 on the beds. The Pseudomorphous crystals of salt tell 

 of the evaporation of pools by solar heat, for neither 

 crystals of chloride of sodium (salt"), nor deposits of 

 sulphate of lime (gypsum), could have been formed 

 amid common mechanical sediments at the bottom of 

 an open ocean. Only concentration of salts, by solar 

 evaporation of inland waters, could have produced this 

 result. 



Eight genera and 21 species of fishes have been 

 found, chiefly in the marl slate. They are Acro- 

 lepis 1, Calacanthus 2, Dorypterus 1, Gyracanthus 1, 

 Gyropristis 1, Palceoniscus Il,Platysomus 2, and Py- 

 gopterus 2. Grenerically they have strong affinities 

 with those of the Carboniferous age, some of which were 

 undoubtedly truly marine, while others certainly pene- 

 trated shallow lagoons bordered by peaty flats. There 

 is nothing extraordinary in the occurrence of seafish 

 in an inland salt lake. 



