Murchison on the Permian System. 269 



between the fossils of succeeding formations cannot be referred 

 to physical revolutions of the surface ; for in the examples cited 

 there is a sequence of congeneric remains, where the succession 

 of the strata has been powerfully interrupted (Carboniferous to 

 Permian), and a total change of fossils where the contiguous forma- 

 tions are conformable (Permian to Trias.) 



These relations are expressed in this diagram : — 



.. ____^ Keuper, . . .^ 



C \ Muschelkalk, . I 



Lower secondary. 1 j^SSggj Upper Bunter, f 



J 2.^ ; ^_ J_J-Tr V (Gres bigarre) J 



f =^^jrj|§g S^.\ Lower Bunter, ... .1 



UPPER PALEOZOIC <{ ^^^^^ ^ Zechstein, J-permian. 



' L W^jJZZZ^^ Hote-todte-liegende, J 



— * — -c^rr-^.r'^v CARBONIFEROUS. 



The Permian fauna is then considered, and is said to exhibit the 

 last of the successive alterations which the Palaeozoic animals under- 

 went before their final disappearance. The total number of Per- 

 mian species known to the authors in different parts of Europe 

 (without reckoning certain ichthyolites not yet named, and a few 

 doubtful forms of shells) is 166, of which 148 are characteristic of 

 the system, 18 only being found in the subjacent Palaeozoic rocks. The 

 Brachiopods being viewed as the shells of most value in determining 

 the durations of the ancient rocks, it is stated, that 10 out of the 30 

 Permian species are common to this system and the carboniferous. 

 After some observations on the species of Productus, Spirifer, Orthis, 

 Terebratula, Lepsena (Chonetes), which have lived on from earlier 

 periods, it is remarked that no form of the Pentamerus, a genus pe- 

 culiarly characteristic of the Silurian strata, has yet been found in the 

 Permian strata, whilst the Brachiopod most frequent in the latter is 

 the Productus, a genus very abundant in the carboniferous or conter- 

 minous deposits, but unknown in the Silurian. Among the Conchifers 

 (26 in number) the Modiola is very characteristic of the Permian 

 system, both in Russia and England ; and though the large species 

 of Axinus so well known in England has not yet been found in 

 Russia, its place is there taken by two other species of the same 



