Ixxvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



rich Upper Silurian limestones of Bohemia have no true representa- 

 tives in Thuringia. Again, whilst the Hartz contains all the members 

 of the Devonian rocks, with a copious development of the Lower 

 Carboniferous, and whilst the Thiiringerwald possesses neither the 

 Central nor Lower Devonian bands, none of these formations have 

 yet been found in Bohemia, where the Silurian rocks are at once and 

 abruptly followed by the upper coal-beds. 



We thus see at what different epochs the breaks occur in the older 

 rocks of Germany and France, and in the palaeozoic series of Great 

 Britain. But the authors observe that, notwithstanding all these dif- 

 ferences, whether consisting of such local dismemberments or varied 

 lithological conditions, the four natural palaeozoic groups of Russia, 

 Scandinavia, Germany, and France have been perfectly assimilated 

 to their congeners in Britain ; so that, despite of great breaks in each 

 natural division of these regions, the classification by means of 

 Silurian, Devonian, Carboniferous, and Permian remains is every- 

 where maintained. 



I would direct the careful attention of those geologists who may 

 be disposed to connect the great and general mutations of life with dis- 

 ruptions and disturbances similar to those here alluded to, to the con- 

 cluding observations of this paper. The authors state that, in Ger- 

 many no physical dismemberment has been observed which separates 

 the upper palaeozoic strata, accumulated at the close of the Permian 

 epoch, from the lowest mesozoic strata, formed during the earliest 

 period of the Trias, the summit of the one being everywhere con- 

 formable to the base of the other; and yet the change of life which 

 took place at that period of quiet physical transition was absolute and 

 complete. 



It does not however necessarily follow (and I am not certain whether 

 the authors mean to infer it or not), that these Upper or Triassic 

 beds immediately followed the deposition of the Permian. For, 

 although no disturbances or change of inclination of the strata may 

 have taken place, an indefinite period of time may have elapsed be- 

 tween the deposition of the two formations ; that such was the case 

 is indeed rendered probable by the great change of organic life ob- 

 served between these two formations. But no evidence of such a 

 lapse of time would be forthcoming if the lower bed had maintained 

 its horizontality during the intervening period. 



We have not yet received the completion of the text of the Drs. 

 Sandberger's work on the ' Fossils of the Rhenish Devonian System 

 in Nassau,' but I understand that we may soon expect it. In the 

 mean time, Dr. G. Sandberger has forwarded to me a catalogue 

 of the principal fossils figured in it, and which may serve as cha- 

 racteristic types of the formation. To this he has added a table of 

 contents, from which it appears that the following organic remains 

 are to be described in the work : — 



Genera. 



Pisces 2 



Crustacea 11 



Annulata 2 



Species. 



Newly described. 



2 





19 . 



6 



8 . 



5 



