22 



GEOLOGICAL MEMOIRS. 



In the second place, the fauna of the Lower Oligocene, as far 

 as the author was able to judge in his journey to Latdorf, seemed 

 to be singularly analogous to the fauna, not of the first maiine 

 beds of the Fontainebleau sands, but to those of Morigny, near 

 Etampes, superior to the marine marls of Montmartre. Erom 

 Latdorf about lorty species were obtained, and the author has not 

 been able to establish the identity of one of them with Eocene 

 forms. While admitting that the fauna of the Lower Oligocene 

 may be anterior to that of Morigny, he considers that there is still 

 enough margin between this zone and the gypsum in which to 

 class it, without separating it from the Lower Miocene ; for in the 

 Paris basin, between the horizon of Morigny and the freshwater 

 marls above the gypsum, which M. Hebert considers as the upper 

 limit of the Eocene, there are, (1) sands and marls with Natica 

 crassatina, Deshayesia cochlearea, Brong., &c. (2) Freshwater lime- 

 stones and " meulieres " of Brie. (3) Green and yellow marls with 

 Cyrena convexa, Brong. sp., Psammohia plana, Brong. sp., Ceri- 

 thium pUcatum, Lam., C. trochleare, Lam., Bithynia plicata, d'Arch. 

 and de Yerneuil, sp. 



There is not sufficient reason to place the Lower Oligocene below 

 the last of these. 



The lignites upon which the marine beds of Latdorf rest, and 

 generally the Lower Oligocene, may, the author admits, possibly cor- 

 respond to the gypsum, although it is impossible to assign a definite 

 place to it until after the discovery in it of organic remains. He 

 also thinks that the beds of Limbourg may be ranged with the 

 Middle and Lower Oligocene of M. Beyrich, but considers that too 

 much haste has been shown in identifying the Lower Oligocene of 

 Belgium and Germany with the U]3per Eocene of England, especi- 

 ally with the Barton clay. 



The idea of a general catastrophe putting an end to the Eocene 

 fauna, which had been attributed to the author by M. Beyrich, is 

 denied, and a more gradual operation, such as accompanies all general 

 movements of the surface, is maintained to have been the cause. 

 The author then gives a Table showing the correlation of the beds 

 belonging to the Lower Miocene in France, Germany, and Belgium. 



Upper bed .. 

 ^ « Middle bed.. 



I Lower bed 



Upper Eocene ... 



Middle Eocene(up- 

 per bed) 



France. 



Beauce limestone. 

 Sands of Etampes . 



Erie limestone and 

 marls with Cy- 

 renaB 



■j Gypsum i 



Beauchamp sands 



Germany. 



Upper Oligocene . 

 Middle Oligocene 



V Lower Oligocene 



? Lignites of Lat- 

 dorf, &c 



Missing 



Belgium. 



Upper Limbourg. 



Lower Limbourg. 



I- Missing. 

 Missing. 



M. Hebert attempts to show that it is more probable that the 

 Middle Oligocene of the basin of the Ehine, and of Switzerland is 

 related to the beds of Tongres and of Maestricht than, as M. Bey- 



