122 THE STORY OF THE EARTH. 



which is impervious to water. The gypsum has 

 probably been formed out of the carbonate of 



lime of calcareous organisms, by the action upon 

 them of sulphurous waters, such as result from 

 the decomposition of iron pyrites, for Mr. Charles 

 Darwin describes gypsum as formed in this way 

 in lakes on the surface of South America. 



In the neighbourhood of Storeton, between 

 the Mersey and the Dee, an immense number of 

 impressions of the feet of terrestrial animals are 

 found, some of which are at present otherwise 

 unknown. They may comprise the footprints of 

 Dicynodonts, of Rhynchosaurian reptiles, and per- 

 haps of Hyper odapedoHy bones of which occur in 

 Keuper beds in other parts of the country. The 

 Keuper at Warwick yields evidences of the skull 

 of species of Labyrinthodon. And near Bristol, 

 carnivorous saurians, termed Pal<EOsaurtls % with 

 piercing and cutting teeth, are found, which are 

 clo>ely allied to the great saurians of the Trias of 

 Wurtemberg, named Zandodon* 



The Stormberg beds in South Africa are prob- 

 ably of TriassiC age, and contain saurians in some 

 ects similar to those of Germany, such as 

 Massospondylus and Euskelesaurus } and are found 

 above the Coal Of Cape Colony. They all show 

 some alliance with the M VTUS ^i a later 



saurians of the Miisehelkalk in Germany 



inclu le /' i fiw, which has the palate covered 

 with large flat crushing teeth; and NothosauruSy 



Which appear to be intermediate between the 



l>- iter iurj of the underlying Permian rocks 

 and the long-necked Plesiosaurs of the 



Oolith 



Jul ast the plants of the coal period, 



