AUSTEN ON THE BOULONNAIS. 231 



On the Series o/" Upper Paleozoic Groups in the Boulonnais. 

 By Robert A. C. Austen, Esq., F.R.S., Sec.G.S. 



[Read March 23, 1853*.] 

 [Plate X.] 



In May 1852 I accompanied Prof. Edward Forbes, Mr. Prestwich, 

 and Mr. Morris in a geological excursion into the Boulonnais and 

 part of Belgium : the examination which we were enabled to make 

 of the district about Marquise, though brief, was sufficient to satisfy 

 us that the Palaeozoic group there had not been described with suffi- 

 cient precision and detail. I therefore visited it again in the autumn 

 of the same year, and on that occasion I was joined for several days 

 by Mr. Daniel Sharpe. 



The Lower Boulonnais is a district of the province of Artois, which 

 has for its natural limits the escarpments of the chalk formation : its 

 breadth from north to south, as from Wissant to Verlinctun, is about 

 fourteen miles ; and its length, from Bovilogne to Lottinghen, about 

 twelve. This district has been of interest to the English geologist, 

 since its physical features were first noticed by MM. Conybeare and 

 Phillips, as it constitutes the eastern extension of our Wealden denu- 

 dation. In the extreme north-east angle of this area, a little beyond 

 the village of Marquise, and at the very base of the chalk escarpment, 

 there is a very limited tract, which is the subject of the present com- 

 munication. See Map, Plate X. 



The palaeozoic rocks of the Boulonnais were described by M . Rozet 

 in his general memoir on that district, and they occupied much of the 

 attention of the French and English geologists during the Reunion 

 Extraordinaire at that place in 1839. 



M. Rozet attempted to place the Boulogne series in accordance 

 vdth the popular systematic arrangements of the carboniferous rocks 

 of England, and this led him into error. The account of the Bou- 

 logne Meeting, contained in the Bulletin of the French Geol. Soc. 

 vol. ii. 1840, must be separated into two portions of very unequal 

 authority — the one being that containing the views and observations 

 of the geologists then present — the other a communication from 

 M. Souich, a resident mining engineer, and full of accurate state- 

 ments respecting the structure of the district. 



In 1838 M. de Verneuil published an account of a section from 

 Marquise to Landrethunf, in which the lower subdivisions of the 

 Palaeozoic series were identified as the equivalents of the several parts 

 of the " Silurian System," and this view was adopted and confirmed 

 by Sir R. Murchison when at the Boulogne Meeting in the following 

 year. At the close of that Meeting a small collection of the fossils 

 of the Ferques and Fiennes limestones was sent to Mr. Lonsdale for 

 examination, and he at once recognized their agreement with certain 

 forms from South Devon, which in the previous year had been taken 

 as the types of a " Devonian System." This rectification was adopted 

 by Sir R. Murchison in a paper read to the French Geological Society 

 * Vide supra, p. 115. f Bull. Soc. Geol. de Fr. 



