Von Koenen — Belgian Tertiaries. 503 



as mucli as possible -witli the well-named fossils of his country, 

 in this case especially, with the shells from the Scaldisien. On the 

 other side I must maintain that every Tertiary horizon has as many^ 

 species in common with the succeeding as with the preceding 

 horizon, that is to say, if they are analogous deposits, and provided 

 there he no sharp lines of division separating them, either into two, 

 three, or four periods, according to the author followed, whether 

 it be Dr. Hoernes, Sir Charles Lyell, or Professor Beyrich. The 

 division of Professor Beyrich into four periods is in accordance with 

 the geological distribution of the different beds, and has the advan- 

 tage that the names of the periods, Eocene, Oligocene, Miocene, 

 Pliocene, joined to the words Upper, Middle, and Lower, are suffi- 

 cient to distinguish all the principal horizons of the Tertiaries. 



If, therefore, the Systeme Diestien resembles the Coralline Crag 

 as much as the Coralline Crag resembles the Eed Crag, that is not a 

 reason to put the Systeme Diestien rather into the Pliocene than into 

 the Miocene. Mr. Lankester proposes to put certain beds of the 

 Vienna basin, which he concedes to be coeval with the Systeme 

 Diestien, also into the Pliocene ; but in doing so, in order not to 

 withdraw one of the Antwerp beds from the others, he tears in 

 two the Vienna beds, which are most certainly identical with the 

 " Faluns de la Touraine," the type of the Miocene, and older than the 

 Snbapennine and Crag beds, which are the type of the Pliocene. 



I must, say at the same time, that the name of Crag noir ought 

 not to be employed instead of Sable noir or Systeme Diestien, 

 because these beds do not correspond, either in age, condition, 

 appearance or contents with the English Crag. 



The sub-division of the Sable vert ought to be abandoned, because 

 the greenish colour is caused only by the weathering of the black 

 glauconite of the Sable noir, and beca^^se the Sable vert lies some- 

 times below the Sable noir, and contains, moreover, the same fossils, 

 though generally only in the state of casts, the oysters (Gryphaa 

 navicularis) alone having the shell preserved. In short, Mr. Lan- 

 kester very correctly states the difference of the Systeme Diestien 

 from the Coralline Crag, and its identity with beds generally reputed 

 to be of Miocene age ; an identity first announced by me in 1863.^ 

 But I have since then found that Professor Eeuss, of Vienna (one of 

 the best authorities upon Foramimfera, AntJiozoa, and Bryozoa), had 

 already pointed out (in his paper " On the Foraminifera, etc., from 

 the Systeme Diestien and from the Miocene of the North of Ger- 

 many), the great analogy between their fauna. The identity of the 

 Sable noir with the beds of Eecken and Winterswyk in the South- 

 east of Holland has been long ago recognised by Messrs. Nyst and 

 Bosquet. A few miles from Winterswyk, near Dingden^ (north 

 of Wesel), there appear black marly sands (not passed through by a 

 well-boring, in a thickness of 120 feet), containing a very rich fauna, 

 quite similar to that of the Systeme Diestien, but containing, besides 



1 About 40 per cent, it appears. ^ Zeitschr. d. D. Geol. Ges. p. 460. 



3 See Beyrich, " Ueber die Zusammensetzung der Norddeutschen Tertiaerbil- 

 dungen." Abhandl. der Koenigl. Acad, zu Berlin, 1856. 



