230 Geological Society : — 



magnesia might have been deposited simultaneously by concentra- 

 tion of solutions, due to evaporation. Some of the MagDesian-Lime- 

 stone strata have almost a tufaceous or stalagmitic aspect, as if de- 

 posited from solution. 



The Cambrian strata also show some evidence of not being true 

 • marine deposits. They are purple or red, like the other strata pre- 

 viously spoken of; and the surfaces of the beds sometimes exhibit 

 sun-cracks and rain-pittings. The trilobite Palceopyge JRamsayi is 

 considered by the author to be an accidental marking, simulating 

 the form of a trilobite ; and the fossils of St. David's are found in 

 grey beds, which may mark occasional influxes of the sea, due to 

 oscillations of level. 



The foregoing reasonings, in the author's opinion, lead to the con- 

 clusion that in the northern hemisphere a continental area existed, 

 more or less, from the close of the Silurian to the end of the Triassic 

 epoch, and that this geographical continuity of land implies probable 

 continuity of continental genera. 



There is therefore no palseontological reason why 'the Hypero- 

 dapedon, Telerpeton, and Stagonolepis of the Elgin country should 

 be considered of Triassic age, especially as the beds in which they 

 occur are stratigraphically inseparable from the Old Eed Sandstone. 



Finally, terrestrial and marine European epochs were rapidly 

 reviewed. 



1. The Cambrian epoch was probably freshwater. 



2. The Old Eed Sandstone, Carboniferous, Permian, and Trias 

 were formed during one long continental epoch. 



This was brought to an end by partial submergence during the 

 Jurassic epoch; and by degrees a new continental area arose, 

 drained by the great continental rivers of the Purbeck and "Wealden 

 series, as shown in various parts of Europe. 



3. This continent was almost entirely swallowed up in the Upper 

 Cretaceous seas. 



4. By subsequent elevation the Eocene lands were formed ; and 

 with this continent there came in a new terrestrial fauna. Most 

 of the northern half of Europe since then has been continental, and 

 its terrestrial fauna essentially of modern type. 



If, according to ordinary methods we were to classify the old 

 terrestrial faunas of North America, Europe, Asia, and probably of 

 Africa, a palaeozoic epoch would extend from Old Eed Sandstone to 

 Wealden times, and a Neozoic epoch at least from the Eocene period 

 to the present day. The Upper Cretaceous strata would at present 

 remain unclassified. The' marine epoch would also temporarily be 

 divided into two, Palaeozoic from Laurentian to the close of the 

 Permian times ; and all besides, down to the present day, would form 

 a Neozoic series. The generic gaps between the two begin already 

 to be filled up. The terrestrial and the marine series at their edges 

 at present overlap each, other. 



The great life-gaps between the two terrestrial periods may some 

 day be filled up by the discovery of the traces of old continents 

 containing intermediate developments of structure as yet undis- 

 covered. 



