154 Seeley— Section of the Lower Chalk near Ely. 
contrary to the physical consideration ; but to say they sup- 
ported the hypothesis of a shallow sea ‘would assert too much. 
As a group, they differ but little from other Lower Chalk 
collections, and offer little or no ground for assuming theories 
as to relative depth in the Lower- “Chalk Ocean. 
At Cherry-Hinton the Chalk-pit is about 30 feet above the 
Greensand. At Madingley there is a chalk-pit much lower in 
the Chalk; and in this locality the lower beds are less compact, 
have a slightly marly character, and contain Rhynchonella lineo- 
lata. In this pit there are lines of bedding which dip south; 
and here the Chalk forms a hill overlooking the whole Fen- 
country; the Greensand cropping out a few yards below, and a 
great plane of Gault extending beyond to the north. The hills 
Gf che’owen Chalk are alll low - ; Cherry-Hinton Gog-Magog, 
which is the highest, being only some 200 feet; and all the 
higher part of this is of Upper Chalk, which formerly, full of 
flints, was also seen in the Cherry-Hinton pit, but has been 
quarried away. ‘The Lower Chalk contains some small frag- 
ments of vegetable remains, but no plant more definite than the 
dubious Chondrites. I have never seen any extraneous speci- 
mens excepting a phosphatic nodule from Reach, derived from 
the Upper Greensand; and it fortunately is a phosphatized 
Cucullea, of a different species to any yet detected in the 
Cambridge district. The Gasteropods have come chiefly from 
Burwell. Crustacea occur indifferently at Burwell and Cherry- 
Hinton; as do Cephalopods, though these are much more 
abundant at Burwell than anywhere else. 
Til. On THE LAURENTIAN ForRMATION: ITS MINERAL CONSTITUTION, 
ITs GEOGRAPHICAL DISTRIBUTION, AND ITS RESIDUARY ELEMENTS 
or Lire. By J. J. Brassy, M.D., F.G.S., formerly British Se- 
cretary to the Canadian Boundary-Commission. 
PART I, 
lle is intended in this paper to present a general outline of the 
Laurentian Formation under the heads mentioned in the above 
title ; dwelling principally on the latter clause, its residuary elements 
of life, or, in other words, on those mineral substances, contained 
within it, which at some earlier period have been the constituents of 
organic bodies. This formation, or system of rocks, which have 
been called ‘ fundamental,’ has of late years very generally received 
the name of ‘ Laurentian,’ a geographical denomination, taken from 
the country (Laurentide or Laurentian Mountains) in which it has 
been well studied, and where it exists in vast force. An assemblage 
of metamorphosed rocks may usually be considered ‘ Laurentian,’ 
when over great spaces (with or without the intervention of the 
