60 PERMIAN ERA. 



* 



in the ancient seas, or only to some such simple cause as the 

 occurrence of deposits which were not favourable to the pre- 

 servation of animal remains. It may even be that the principal 

 cemeteries of the age have not yet been hit upon by research ; 

 for certainly this is neither the most extensively nor the most 

 rigidly examined of the various formations, and we are made 

 the more suspicious by finding that, at this part of the rock 

 series, several important fossiliferous strata are present in one 

 region and not in others. It has been ascertained, however, 

 by Permian researches, that extensive changes of specific forms 

 in the ancient seas were not, as has been supposed, necessarily 

 and essentially connected with great physical disturbances ; for 

 both do we find that the unconformability of strata or memo- 

 rials of disturbance between the carboniferous and Permian do 

 not affect the fossils, and that a conformable succession of 

 strata over the Permian is attended by a great usually called 

 a complete change of species. At this termination of the 

 Permian, it has become customary to close what is called the 

 Palaeozoic Period, or period of the most ancient forms of 

 animal existence, on a presumption that a completely new set 

 now enter upon the field. There seem, however, to be con- 

 siderable reasons for doubting if any such decided change takes 

 place at this point of time. Plants identical with species of 

 the carboniferous formation are found in later formations 

 (Trias of France and certain Liassic beds in the Alps). We 

 have also seen that reptiles of a family hitherto supposed to 

 commence in these superior formations are now discovered in 

 the carboniferous beds. In that regular advance of life from 

 inferior to superior classes there is here no interruption. 

 Taking all things together, it seems the more reasonable sup- 

 position, that, notwithstanding conformableness of strata, a 

 local suspension of deposits for a considerable time is indi- 

 cated a time during which the usual changes of species were 

 proceeding probably at their usual rate and which was 

 sufficient to present something like a complete change of forms 

 when the deposits were re- commenced. 1 



1 Murchison's Russia ; also Mr. Horner's address as president of the 

 Geological Society, Feb. 1846. 



Russia presents another notable example of a change of fossils in a 

 conformable series of strata ; that is, a series showing no record of vol- 

 canic disturbances. This takes place between the Devonian and Car- 

 boniferous formations. " The uppermost beds of the Devonian," says 

 Sir R. Murchison, " loaded with Holoptychius and Onchus, Coccosteus, 

 Placosteus, and Dendrodus, are at once conformably surmounted by 



