246 MIOCENE STEATA OF ITALY. [Oh. XIV. 



In one instance, the pattern of a butterfly's wing has escaped oblitera- 

 tion in the marlstone of Eadaboj ; and when we reflect on the remote- 

 ness of the time from which it has been faithfully transmitted to us, 

 this fact may inspire the reader with some confidence as to the reli- 

 able nature of the characters which other insects of a more durable 

 texture, such as the beetles, may afford for specific determination. 

 The Vanessa above figured retains, says Heer, some of its colors, and 

 corresponds with V. Hadena of India. 



The lignites called Brown Coal in Germany belong, for the most 

 part, to the Lower Miocene epoch. Among these may be mentioned 

 those of the Siebengebirge, near Bonn, which are associated with 

 volcanic rocks. 



Professor Beyrich, in his important " Memoirs on the Tertiary 

 Strata of the North of Germany," * has made known to us the exist- 

 ence of a long succession of marine strata which lead, by an almost 

 gradual transition, from the Sternberg beds (see above, p. 239), 

 approaching in age to the faluns of the Loire, to others agreeing in 

 date with the Lower Tougrian of Dumont, already mentioned, p. 238,' 

 as the base of the Miocene. In conformity with the method which I 

 formerly adopted, he has appropriated the term Miocene exclusively 

 to the faluns of Touraine and strata of that age ; but for all the for- 

 mations below that level^ as far down as the Uppermost Eocene, he 

 has proposed the new term of Oligocene. The Sternberg beds are 

 called Upper Oligocene ; the next five groups, to which those of the 

 Mayence basin, amongst others, belong, as well as the Calcaire de la 

 Beauce and Fontainebleau Sandstone, are named Middle Oligocene ; 

 while the Egeln beds and some North German Brown Coals of the 

 age of the Lower Tongrian of Dumont are called Lower Oligocene. 

 The difficulty of drawing a boundary line between these last forma- 

 tions and the Eocene is precisely the same as that of separating the 

 Lower Miocene and Eocene (as defined in the preceding chapters) in 

 France and Belgium. After full consideration, it seems to me most 

 convenient to accept the classification so long adopted by many wri- 

 ters, which places the gypsum of Montmartre as the uppermost of the 

 Eocene subdivisions ; and if it can be demonstrated that any part of 

 the Tongrian of Dumont, or of the German strata classed by Beyrich 

 as Lower Oligocene, is strictly contemporaneous with the Paris gyp- 

 sum or the Bembridge strata of the Isle of Wight, I should then sepa- 

 rate them from the Lower Miocene, and consider them as Upper 

 Eocene. We are now arriving at that stage of progress when the 

 line, wherever it be drawn, will be an arbitrary one, or one of mere 

 convenience, as I shall have an opportunity of showing when the 

 Upper Eocene formations in the Isle of Wight are described in the 

 sixteenth chapter. 



* Abhandlungen der Konigl. Acad, der Wissen. zu Berlin, 1855, and ibid. 1858, 

 p. 59, 



