HUBERT NUMMULITIC AND OLIGOCENE STRATA. 21 



southern part, and vice versa, during which the deposition of the 

 several beds was taking place. 



In the long succession of faunse and physical phenomena de- 

 scribed by M. Hebert, it is between the Nummulitic fauna of the 

 High Alps and that of Castel-Gomberto that the greatest difference 

 is manifested, and it is there where M. Pareto, incorrectly as the 

 author thinks, places the limit between the Miocene and the Eocene. 



An intimate relation exists between the beds of Castel-Gomberto 

 and Salcedo, and the Upper Nummulitic beds of the Bormida, and 

 between these latter and the true Miocene of the Superga, and of 

 Leognan, or of Touraine. 



An altogether analogous succession unites together, in Aquitaine, 

 Gaas and Leognan, and M. Hebert considers that at present it does 

 not appear necessary to add to the three great divisions of the Tertiary 

 a fourth — the Oligocene, — which is included in his Lower Miocene. 



If in the north of Europe this Oligocene presents great differences 

 from the Miocene (Middle Miocene), it only shows that the upper 

 part of this group is not generally represented by a freshwater forma- 

 tion ; but the continuity is found again in the south, and there it is 

 not possible to admit the Oligocene. There is not then sufficient rea- 

 son to change the ternary division of the Tertiary strata, and the 

 best line of demarcation between the middle and lower group will 

 remain that which, in a general manner, M. Elie de Beaumont has 

 indicated, namely, below the Fontainebleau sands, and which the 

 author has attempted to define more clearly by fixing it between 

 the freshwater marls above the gypsum, and the marls with Cyrena 

 convecca and Cerithium plicatum, &c., below the Calcaire de Brie. 



A paper by M. Beyrich, published in 1858, in the " Berichte " of 

 the Academy of Berlin*, is then noticed by M. Hebert, who says 

 that the author has, in some instances, given to his statements a 

 meaning which was not exactly intended. Eor instance, his opinion 

 that although the sea of the Faluns of Touraine differed as much 

 from the sea of the Fontainebleau sands, as these from the sea of the 

 *' Calcaire grossier," it was preferable to adhere to the ternary divi- 

 sion, has been rendered altogether differently in the German text. 



M. Beyrich has placed the Fontainebleau sands as the equivalent 

 of his Middle Oligocene, and the gypsum of Montmartre as syn- 

 chronous with the Lower Oligocene, which would be represented in 

 Belgium by the lower beds of Limbourg. This classification, M. 

 Hebert thinks, cannot be justified by facts. First of all, in the 

 Paris basin the gypsum belongs certainly to the lower part : — 



(1) By the marine bands intercalated with its lower beds, of 

 which the fauna is identical with that from the marls with^ Phola- 

 domya Ludensis, which belong to the Beauchamp sands ; (2) by 

 the freshwater beds above the gypsum, the fauna of which ap- 

 proaches nearer to that of the Saint- Ouen limestone, situated below 

 the gypsum, and the marine marls with P. Ludensis, than of that 

 of the Brie limestone ; (3) by the contained Mammifers, which it 

 would be difficult to associate with those from the Beauce lime- 

 stone, this being the consequence of classing the latter as Upper 

 Oligocene, and the gypsum as Lower Oligocene. 



* See also Quart. Journ. Geol. Soc. vol. xx. Part 2, Ui^iscell. p. 5* 



