240 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



3. Bright red shales and clays underlie the sandstone, as may be 

 seen in the quarry near the Chateau de Fiennes ; and this band may 

 be traced across the district at intervals, by the colour it imparts to 

 the surface soil, as near La Malassise, and west of Ferques, where 

 the iron ore is raised. 



These red shales are succeeded or pass into others of a dark grey 

 tint : the superficial breadth of this argillaceous group is about 1 70 

 yards, which with a mean dip of 20° gives it a thickness of about 

 180 feet. 



Limestone of Ferques and Fiennes. 



Strictly speaking it is the Haut-banc limestone which is nearest to 

 the village of Ferques ; the band now in question passes it at some 

 distance on the north-east. This limestone is not separated by any 

 very marked line from the group next above it ; some of the charac- 

 teristic shells of this second division of the Boulogne series (To'cbra- 

 tula, Spirifer) are most abundant in the shales, which overlie the 

 limestone, and belong to the higher group ; with these are isolated 

 masses of coral in lenticular masses, representing the gradual cessa- 

 tion of conditions favourable to their increase. 



The pure limestones are very distinctly stratified throughout ; the 

 upper portion is thin-bedded, and the intervals would seem to indi- 

 cate periods of time when accumulation ceased ; the duration of 

 these may be estimated, as it is mostly in the upper portions of each 

 of these beds that these large coral masses, with perfect terminal 

 surfaces, are met with, and which are so characteristic of this band. 

 The middle portion of the band presents one or two distinct zones 

 of Spirifers : the lower beds are thicker, darker, and afPord orna- 

 mental marbles, besides being worked into pavement slabs. This lime- 

 stone band is the only portion of the series which can be traced 

 continuously across the area of the older rocks ; it is also more 

 extensively quarried than any other : near La Malassise it ranges 

 for a short space rather E. and W. of its usual strike, thence it runs 

 nearly N.W. S.E. as far as the fault along the Beaulieu stream ; it 

 crosses the Bois de Beaulieu W. 10° N. and runs out in the Crem- 

 breux stream at the Chateau de Fiennes. 



In its range from west to east the inclination of this band presents 

 at intervals 8°, 10°, 20°, 25°, and lastly at the Crembreux stream 

 as much as 35°. 



The abundance of the fossil forms preserved in this band places 

 it in striking contrast with the higher limestones, but they are 

 not equally distributed throughout — the upper portion is by far the 

 richest. 



The following list of species contains only the result of Mr. Sharpe's 

 examination of what we ourselves collected ; in the general list there 

 will be found others quoted on the authority of competent observers, 

 but even that gives a very imperfect notion of the richness of the 

 fauna of the Fiennes baud. The collection of M. Bouchart of 

 Boulogne contains numerous forms which we were not able to meet 

 with, and of which it is understood that he proposes to publish a 



