Correspondence— Mr. G. F. Doll/us, F.C.G.S. 91 



This opinion is repeated in various other publications ; we can 

 see in the explanation of the geological map of Belgium, published 

 by Dumont, in 1892, the following lines : " Miocene = System 

 Bolderian — gravels, glauconiferous sands, white sands, shelly 

 gravels, and various other sands." 



In Dumont's private notes, published not many years ago by 

 M. M. Mourlon, we find the same version. Dumont says in his 

 ■description of the Bolderberg Hill : " This gravel contains pebbles 

 of flint from the size of a nut to the size of an egg, and a great 

 many shells more or less well-preserved; they were living during 

 the time of the deposition of the sand in which they are found." 



We could multiply these quotations, but when Mr. Dewalque 

 says that the Bolderian is a white unfossiliferous sand, he 

 speaks of his Bolderian, but not of the original Bolderian of 

 Dumont. On the other hand, the Bolderberg fauna is clearly 

 Upper Miocene, we find that this fauna is extremely close to the 

 fauna of Edeghem sands, near Antwerp, of which the malacological 

 fauna has been described by Nyst. in 1861, as true Miocene. More 

 than 90 per cent, of the species are common to the two localities, 

 and we think there is good ground to say that the Bolderian was 

 contemporaneous with the Anversian. The term Anversian was 

 introduced into the science by Mr. Cogels, in 1879, to indicate the 

 level of the Edeghem sand, or lower black sands of Antwerp. 



We will give the names of some of the most typical shells found 

 in the Bolderberg : — 



Murex aquitanicus, Grat. Conus Dujardini, Nyst. 



Terebra Basteroti, Nyst. Voluta Bolli, Kock. 



Cancetlana cancel/ata, L. Anci/laria obsoleta, Br. 



,, acutangularis, Lk. Oliva Dufremei, Bast. 



,, imbricata, Hoerues. Turbo murieaius, Duj. 



Dipsaccus Brugadinus, Grat. Natica Josephinia, Bisso. 



JPleurotoma asperulata, Lk. Venus multilamellar Lk. 



,, denticulata, Bast. Cytherea ehione, Lk. 



,, ramosa, Bast. Corbulu carinata, Duj. 



,, festiva, Dod. Corbulomyu complanata, Sow. 



Pectunculus pilosus, L. Ostrea erassissima, Lk. 



It will be at once clear to any geologist that the age of this fauna 

 must be Miocene; it certainly cannot be Oligocene. This is a warm 

 (southern) fauna, very distinct from the cold or temperate fauna of 

 the Diestian deposits. The scruple of Mr. Dewalque is based on 

 the fact that in the Bolderberg Hill, the fossiliferous bed (some- 

 times ferruginous) rests upon a thick mass of white sand, and is 

 covered by a great mass of ferruginous sandstone pertaining to the 

 Diestian formation, and Mr. Dewalque does not seem perfectly sure 

 whether the fossiliferous bed pertains to the lower mass, or to the 

 upper one. But we have seen that the old stratigraphists, such as 

 Dumont, had classified the fossiliferous beds with the white sands; 

 and since that time the best contemporary geologists, as Mr. Gosselet, 

 have adopted the same conclusion, saying that the fossiliferous sands 

 have nothing to do with the Diestian or upper beds. 



More recently Mr. Van den Broeck discovered at Waenrode, near 



