DIESTIAN. 
61 
district. He drew my attention to the strong unconformity 
which separates the Diestian beds from any of the older deposits. 
This break was noticeable in the Bolderberg, where the Diestian, 
with casts of its characteristic shells, rests irregularly on fine 
Miocene sand with a line of pebbles and silicified fossils having 
a totally different character. This disturbance of all the beds 
up to and including the Miocene, and their great denudation before 
the deposition of the oldest Pliocene, is an important point, and 
will be again alluded to. 
When we leave the higher ground and descend towards the - 
flat country near Antwerp, we find the beds to undergo a 
gradual change. In the neighbourhood of the city, where they 
underlie the later Scaldisian deposits, they have become quite 
unweathered. Instead of appearing in the form of ferruginous 
sandstone, they consist of soft sand full of glauconite, and contain¬ 
ing abundance of well-preserved calcareous fossils. The difference 
in the lithological character of the deposits is so great, that it has 
only lately been clearly recognized that we are merely dealing 
with weathered and unweathered portions of the same bed. This 
has been principally proved by the researches of Messrs. Cogels, 
Van Ertborn, and Van den Broeck, who have shown that the 
casts found in the neighbourhood of Diest belong to the same 
species as the well-preserved shells found in Antwerp Docks. 
A study of the changes produced by weathering also led to the 
discovery that the line accepted by the older writers as the 
junction of the Scaldisian with the underlying Diestian at 
Antwerp was merely a line of colour. The real junction is 
marked by a band of [)ebbles, across which the supposed boundary 
between the black crag ” and the upper lighter-coloured division 
passes diagonally. On visiting the new Antwerp Docks in com¬ 
pany with Messrs. Cogels and Van Ertborn, I ha(f the opportunity 
of examining the long sections there exposed. I found that 
these observers were undoubtedly right in their contention^ and 
that in preparing lists of the faunas of the two deposits it becomes 
necessary to ignore the lists made before the true line of junction 
was recognized. In the older collections some of the Scaldisian 
o 
species have probably been placed in the lower division; while 
on the other hand some of the Diestian species have wrongly 
been included in the later fauna, owing to their occurrence in 
a light-coloured matrix. Lithologically the Diestian and the 
Scaldisian sands are almost identical, there being no sharp change, 
as there is from our calcareous Coralline Crag to the overlying 
coarsely quartzose Bed Crag. 
Besides this cause of confusion, Miocene beds have been 
touched at the bottom of certain of the Docks at Antwerp. The 
Miocene shells have not always been clearly separated from the 
overlying Diestian, and it is possible that this mixture has helped 
to give rise to the belief in a passage between the Miocene and 
the Pliocene. In reality there appears to be nothing in Belgium 
appro idling to a “ Mio-Plioceneformation. As in England, 
r> 2 
