363 
land), which Mr. Morris has pointed out to the author to be iden- 
tical with the P. marginata of Michaud, a living French species. 
It is a question therefore, the author states, whether these unknown 
fishes may not still mhahit the rivers and lakes of the more northern 
parts of urope or America, especially as M. Agassiz is at present 
unacquainted with the freshwater fishes of Norway, Sweden, Spitz- 
bergen, Iceland, Greenland, Labrador and Canada, and even of the 
northernmost parts of Scotland and the Shetland Islands; and in 
conclusion Mr. Lyell says, it seems natural to look northward for 
types analogous to the Mundesley fishes, because the beds in which 
they occur were deposited contemporaneously with the drift accu- 
mulated by the agency of floating ice. 
Feb. 3.—A paper was read, “‘ On the Geological Structure of the 
Wealden District, and of the Bas Boulonnais,” by William Hopkins, 
Esq., F.G.S. 
This paper is divided into two.parts. In the first the author de- 
scribes the phenomena of elevation presented in the two districts 
comprised respectively . within, the boundary of the great Chalk 
escarpment of the south-eastern part of England, and an exactly simi- 
lar escarpment forming the inland boundary of the Bas Boulonnais, 
The former is well known as extending fromthe coast at Folkstone; 
by Seven Oaks, Godstone, Farnham, Petersfield, etc., round to. the 
coast again at Beachy Head. On the opposite side of the channel, 
the escarpment, commencing at Wisant on the north, forms nearly 
a semicircle, of which Boulogne is not far. from the centre. If we 
conceive the northern Weald, escarpment continued from Folkstone 
to Wisant, and the southern one from Beachy Head to the southern 
extremity of the Bas Boulonnais, it will be seen that. the whole tract 
~ comprised within the Chalk would be a regular oval, except that its 
axis instead of being straight is ewrved, so as to incline towards the 
S.E. in its eastern portion. ‘These two districts are thus connected 
by relative ppsasion not less than by a community of geological cha- 
racter. . 
In the second part of his paper, the author compares the laws 2 
the existing phenomena in these districts with the results given by 
his ‘ Theory of Elevation,’ published in the Transactions of the Cam- 
bridge Philosophical Society (Vol. VI. Part I.). 
I. The lines of elevation in the Wealden district are partly marked 
by an anticlinal arrangement of the beds, and partly by strong flex- 
ures, forming one-sided saddles. .The latter have been termed by the 
author lines of flecure. The central portion of the district is first 
described. The following lines of elevation are found init. 
1. Hastings Line.—This line runs to the north-east. of Hastings 
towards Battle. It has been mentioned by. Dr. Fitton and other geo- 
logists. /The author had not had time.to examine it himself. 
2. Brightling Line.—This is strongly anticlinal, and runs along 
the high ridge of Brightling Down.as far as Heathfield Park, where 
its distinct features are lost.. The author has not ascertained whether 
it is a continuation of the Hastings line. 
