MURCHISON ON THE PERMIAN SYSTEM. 83 



Trias, the one forming the uppermost Palaeozoic stage, the other 

 the base of the secondary deposits. 



After showing that the " Gres de Vosges," as described by 

 M. Elie de Beaumont, is one of the arenaceous equivalents of the 

 Permian system, and after alluding to its development in the 

 neighbourhood of Strasburg and in other parts of Europe, where 

 it is well separated from the Trias, attention is directed to the fact, 

 that as far as researches had yet gone, the Trias is always con- 

 formable to the Permian, whilst the " rothe-todte-liegende," or base 

 of the latter, is frequently unconformable to the carboniferous 

 rocks, on which it rests, and out of whose detritus it has often been 

 formed. These phenomena, say the authors, prove that the most 

 marked distinctions 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 inter- 

 rupted (Carboniferous to Permian), and a total change of fossils 

 where the contiguous formations are conformable (Permian to 

 Trias). 



These relations are expressed in this diagram : — 



r \ Keuper ..,.•[ 



..,,..;■. .;!■■■;..;,' , ry. \ ■', '. ',', V ^\ Muschelkalk • j. TRIAS. 



Upper Bunter | 

 (Oris bigarm) J 



Lower Bunter . . . . ~\ 

 I 

 Zechstein }• PERMIAN. 



Rotbe-todte-liegendJ 



CARBONIFEROUS. 



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

 last of the successive alterations which the Palaeozoic animals un- 

 derwent before their final disappearance. The total number of 

 Permian 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, Leptasna (Chonetes), 

 which have lived on from earlier periods, it is remarked that no 

 form of the Pentamerus, a genus peculiarly 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 conterminous de- 

 posits, but unknown in the Silurian. Among the Conchifers 



G 2 



