THE PERMIAN AND TEIASSIC SYSTEMS. 713 



district of Cheshire, supposes that the sea once flowed up the valley of the Weaver, and 

 was cut off from it by the growth of a bar, again making its appearance by bursting 

 through the barrier, and again the communication ceasing from the same cause. He 

 conceives, therefore, the two beds of rock-salt to have arisen from the two salt lakes thus 

 successively formed, whose waters were dissipated by the natural process of evaporation, 

 and their salt deposited, the intervening and superior strata of indurated clay proceeding 

 from earthy sediments ir. the lakes, deposited after the precipitation of the salt. This 

 hypothesis is supported by the phenomena of many salt lakes in the present day, whose 

 waters are lowering through the supply from springs not keeping up with the expendi 

 ture through evaporation, and whose beds consist of layers of salt, deposited by the over 

 charged water. There can be little doubt that this is the principle upon which the 

 saliferous deposits have been formed, accelerated in its action by a higher atmospheric 

 temperature, and the frequent play of igneous forces, in earlier ages. But the detail of 

 the theory in the case of the Cheshire salt deposits is open to the objection, that it 

 " employs data drawn from the present relations of land and sea to elucidate the pheno 

 mena of a period long gone by, and when from unquestionable evidence it is certain that 

 their relations were generally very different." At the same time, it is quite possible, 

 that in the district in question these relations may have been much the same then as at 

 the present. 



It has been observed, that the new red sandstone series, taken as a whole, is remark 

 ably deficient in the traces of organic life, though, locally, some of its members, as the 

 muschdkalk of Germany, are rich in fossils. The vegetable luxuriance of the carboniferous 

 epoch appears to have died away, though it is true, the paucity of life may be more 

 apparent than real, for it may have arisen from the unfitness of the new red sediments to 

 preserve organic remains in the fossil state. The most numerous relics are those of 

 marine life, which present a new phase in the instance of fishes. Agassiz established the 

 curious generalisation, that the heterocercal tail is universal in the magnesian limestone, 

 and all the older formations ; while in all strata above the magnesian limestone, the 

 homocercal tail predominates, as at present. Eeptiles seem to have been on the 

 increase. In the year 1834, two species were discovered on Durdham-down, near 

 Bristol, in strata belonging to the magnesian limestone the Palseosaurus and The- 



codontosaurus. Relics of a very sin- 

 gular reptile of the lizard tribe were 

 found by Dr. Ward in quarries of the 

 new re< l sandstone at Grinsill, near 

 Shrewsbury the Rhynchosaurus 

 with foot-prints upon the layers of 

 stone in the quarries, supposed to have 

 been impressed by the animal while walking over the surface of the strata, when in a soft 

 state. Parts of the skeletons of Batrachian reptiles, the Greek name for the frog, 

 but of a gigantic size, have been taken from the sandstones of Guy's Cliff, near Warwick 

 and Leamington, of which the cut exhibits a restoration of one species by Professor Owen. 

 The generic name, Labyrinthodon, refers to the labyrinthine inflections of the teeth. In 

 the upper part of the series on the continent, the remains of reptiles multiply; and 

 here, in the muschelkaUc, occur the bones of some large animals of that class the Pro- 

 tosaurus and Phytosaurus. But the most striking peculiarity yet observed is the repeated 

 occurrence of fossil footsteps, or tracks on the sandstone, affording evidence of the 

 existence, at the era of its deposition, of birds belonging to the tribe of Waders, the 

 first indications we have of that highly organised class of vertebrated animals, as tenants 

 of the globe. Ichnites, traces or foot-prints, are characteristic of the new red sandstones, 



