236 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Verrerie, T was assured by M. Buchet, was above tlie coal-measures ; 

 it is inconsiderable in extent and thickness, and represents the lower 

 portion only of the Blecquenecque hmestone. 



S.W. of the Bois d' Aulne the lower limestone rises from beneath 

 the coal-basin of Locquinghen ; it then apparently arches over, as the 

 bed of the watercourse from near La Rochette do^oiwards shows that 

 the superficial covering rests on limestone. A little to the E. of the 

 road from Locquinghen to Rouge-fort there is an old quarry of a 

 black limestone, and which at one time was much sought for as an 

 ornamental marble ; the quarry presents fine beds of compact rock, 

 above which are from 8 to 10 feet of flagstone bands, equally black ; 

 the uppermost bands alternate with two seams of splintery claert, and 

 are overlaid by fine shales ; these beds would therefore seem to corre- 

 spond with those noticed on the road from Rinxent to Blecquenecque. 



The dip of these black limestones is to the S.W. at a considerable 

 angle : a little to the E. of the quarry the basset edges of another 

 limestone may be seen in projecting masses through the cultivated 

 ground, and which presents a remai'kable contrast in colour, being 

 white or nearly so ; it contains large Prodiicti in great abundance 

 (P. auritns, P. giganteus) ; it immediately underlies the black beds. 



The fossils of these uppermost beds of the Haut-banc group are — 



Productus Martini (semireticulatus, Productus fimbriatus. 



Martin). Spirifer lineatus. 



undatus, Defrance. glaber. 



antiquatus. duplicosta. 



plicatilis. bisulcatus, /Sow. 



longispinus (Flemingii, Sow.). Turbinolia fungites ? 



Coal-measnres. — Li the strict order of sequence, this group should 

 have been taken next after the upper limestones of Leulinghen and 

 Blecquenecque, but in a district such as that here described, where, 

 owing to the extent of superficial covering, the succession cannot be 

 followed out at one place, but is to be deduced from a comparison of 

 many sections, the order here taken is most convenient. 



Neither the thickness, nor order of sequence of the series which 

 includes the coal-seams, can be dietermined near Leulinghen and 

 Ferques. The whole of the carboniferous group, as already seen, is 

 highly inclined, and the upper edges have, at some subsequent time 

 to this movement, been planed down to a uniform tabular surface ; 

 at these places, however, the refuse heaps of the old workings suffi- 

 ciently indicate the character of the beds in which the coal is included. 

 A section may be compiled out of a series of scattered observations 

 to be made at the eastern extremity of the Bois des Roches. First, 

 along the line of the watercourse from the black limestone quarry, 

 the lowest coal-shales may be traced, and distinctly overlying the 

 limestone ; above these are the sandstone bands, followed by a consi- 

 derable thickness of light-brown gritty and very micaceous sandstone, 

 to be seen in the road section leading towards Rouge-fort ; these all 

 dip S.W. till they are concealed by the Inferior Oolite, which halfway 

 down the descent to the stream abuts against them horizontally. 

 The strike of these beds carries them in a N.W. course towards the 



