1866.] GOpWIN-AUSTEN BELGIAN TERTIARIES. 235 



face. The upper series is somewhat coarser than the lower, and 

 indicates a local change, or disturbance of sea-bed; the whole of 

 the crag accumulation at this place is sublittoral. 



Along the valley of the Dyle denudation has removed all beds 

 from the Crag down to the Bruxellien of Dumont, or Lower Num- 

 mulitic. 



Fig. 1. — Section showing Crag -sand and Shingle capping a hill east 



of Louvain. 



1. Flint shingle. 



2. Very ferruginous sands, with flint shingle at the base. 



3. White and yellow marl (Argile de Boom) underlain by Lower 



Rupellien sands. 



6. Berg. — The furthest point to the E.S.E. of Antwerp, distant 7 

 myriametres, at which we saw the rolled flints and yellow sands of 

 the Crag-sea area, was at Berg ; these gravel beds were pointed out 

 to us as belonging to the base of the Campine sands, but the circum- 

 stance that the gravel is wholly composed of chalk flints is against 

 such a supposition. These Crag beds, which indicate Kttoral condi- 

 tions, overlie the uppermost portion of the Nummulitic series (Ton- 

 grien). 



7. Bolderherg. — Our visit to this place was the most interesting 

 point of the excursion : the locality had suggested to M. Dumont 

 his *^ Systeme Bolderien ; " as such it was adopted by Sir Charles 

 Lyell {uhi supra, tab. 1. p. 270) as also by MM. d'Orbigny* and 

 Beyricht. The Bolderien formation or division has therefore a two- 

 fold interest : — 1st, in respect of its distinctiveness or place as a 

 marine sedimentary group, 2nd, as to its zoological value. 



The section of the Bolderherg is well given by Bir Charles Lyell 

 {u. s. p. 295), except that the position of the shingle-bed on an 

 eroded uneven surface of the subjacent sandy strata is not repre- 

 sented in the woodcut. To whatever period the lower sands may 

 belong, it is evident that they had become consolidated before the 

 accumulation of the shingle. The shingle is whoUy made up of 

 chalk-flints, in which respect it agrees with the lines of gravel and 

 shingle in the Louvain section (fig. 1), and also with that at 

 Berg. 



M. Dumont's systematic subdivisions were based on considerations 

 of composition or mineral character; and in accordance with an 

 assumed theory of geological change he considered that §hingle-beds 

 represented a break or division in a series of accumulations, and 

 further, that the shingle- or gravel-beds were referable to the close 



* Cours Elementaire de Pal^ontologie, t. ii. p. 765. 



t Ueber den Zusammenhang der Norddeutschen Tertiarbildungen, Abhandl. 

 der k. Akad. der Wissensch. zu Berlin, Aus dem Jahre 1855, pp. 1 et seq. 



s2 



