Mr. De la Beche on the Geology of Part of France. 81 



striking", from the flints being black and disposed in regular layers ; they have 

 not, however, such irregular shapes as the true chalk flints. Even the bed 

 with ferruginous grains, which is here exposed between the other beds, 

 has, in one of the quarries, a white base. Its fossils agree with those in the 

 same bed at Bayeux. 



From Croisy, in a S.S.E. direction, to a small hamlet on the road from 

 Falaise to Pont d'Ouilly, the inferior oolite beds rest upon argillaceous slate 

 and grauwacke. 



The beds of the inferior oolite may in general be traced by a superficial 

 bed of unrolled angular gravel, composed either of flint or chert ; as the one 

 or the other predominates in the oolitic beds of the vicinity. This is par- 

 ticularly remarkable upon the edges of the beds where they rest upon the slate : 

 and on the road from Falaise to Pont d'Ouilly the slate itself is, in several 

 places on the high ground, covered by this kind of gravel, the debris most 

 probably of the inferior oolite beds which once rested upon it. There is a 

 great deal of this gravel between the little hamlet of St. Basille and Tilly sur 

 Seule. 



At St. Laurent de Condel a red porphyritic conglomerate is exposed by 

 the removal of the inferior oolite, which appears at one time to have covered 

 it. The quartz rock and slate of Falaise are also disclosed by a denudation 

 among the same beds ; and there may be many other instances of denudation 

 on the outskirts of the slate hills. 



Lias. 



The lias first appears eastward on the coast of the department of Calvados, 

 between St. Come and Arromanche, under the calcareous sandstone with 

 chert seams above described; from thence to St. Honorine it forms the lower 

 part of the cliffs, gradually rising to the west. At St. Honorine this stratum 

 forms a great curve, and, dipping N.N. W,, disappears on the shore to the 

 west of St. Laurent. Near Port en Bessin it extends to some distance inland, 

 and at the Fosse du Souci, about half a league from that place, the rivers 

 Drome and Aure find a subterraneous passage through it ; reappearing on 

 the coast near Port en Bessin, in the form of large springs or fountains. 



The boundary of the lias in the department of Calvados will be best under- 

 stood by reference to the accompanying map, as the lines which separate it 

 from the rocks above and beneath wind very considerably. Its general direc- 

 tion is south-east from Isigny to Villers. It is extensively quarried along the 



VOL. VI M 



