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.