242 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



•i)=N\t\f>*^jtl Blacourt Sandstone. ' :7t-ct5w?* 



The above limestone is underlaid by shales, which separate it from 

 a compact micaceous sandstone, very closely resembling that which is 

 associated with the workable coal in the higher division of the series. 

 On the section from La Cedule this band contains much diffused 

 carbonaceous matter ; at Blacourt it has impressions of Ferns, where 



I also found a portion of a Calamite ; such indications as these may ij 



have suggested the trial for coal made some years since near Bain- \ 



gheu, and perhaps also that at Caffiers, near which this sandstojitf^ | 



band passes. 'i 1 



Such a change as that here indicated by the intercalation of sands \ 



with a terrestrial vegetation, between two great groups of purely jj '.~ 



marine deposits, presents an instance of the recurrence of the like \ £ 



conditions over the same area. ,; !:, 



The sandstone group is succeeded by shales, which are bright red j! 2 



above, passing into others nearly black : the superficial breadth 'of ij 



this division is upwards of 1 00 yards in the section from La Ce'dule. ^ | 



I was informed at Caffiers, that at the trial-shaft for coal they had 'I 



ultimately met with limestone ; if so, it must have been on this part ,j 



of the series. wimqC' ,«iiJ:'n'"*' < | 



' " ■ ■' ^IdMestone of La Cedule. | 



This is a compact sedimentary limestone, hard and splintery, with ;| 

 frequent interpolations of indurated shale. It rises near the farm of ij 

 La Cedule, and, with the exception of some shales which underlie it, ' 

 is the lowest portion of the Palaeozoic group of the Boulonnais. 

 There is an old quarry, which was worked in the thick middle beds 

 of this zone, and both above and below the beds have more the cha- 

 racter of black limestone shale ; but if we include the whole in the . 

 limestone, it will have a breadth of 56 yards, with a dip to the S.W. ; 

 of from 5° to 8°. •} 



This band is seen for a short distance only ; it crosses the high \ 



road from Landrethun towards Mimoyecques. -; 



The following species were collected from the quarry near La 



Cedule:— " h _ 



Terebratula ambigua. Spirifer disjunctus. | -s; 



reticularis. Orthis resupinata. « 2 



pleurodon. Leptaena Dutertrii. ( ^^ 



Spirifer Boucliardi. I ;-; 



From the foregoing description it will be seen that a narroAV belt 1; " 



only of Palaeozoic strata is here exposed between a portion of the \ 



Oolite series on the S.W. and the Cretaceous series on the N.E., that j 



it has a general strike from N.W. to S.E., and that though it pre- | 



sents two undulations, these are also in the same direction. The i 



several sections taken give the following order of superposition (see \ 



Table) :— ■ 



