248 A. J. Jukes-Browne—The Subdivisions of the Chath. 
degree of relationship between the Corallian Gasteropoda and those 
of the fossiliferous horizons which preceded the Corallian beds 
within the area. Tables of fossils may guide us to a certain extent, 
but owing to many causes, more especially to the binomial system 
of nomenclature, the mere names of fossils afford but little insight 
into their differences and affinities. 
The earliest collectors amassed a heap of curios, and for a long 
time doubted their organic origin. The second stage of observation 
was influenced and obscured by certain prejudices, but the third 
stage witnessed the establishment of the principles of stratigraphical 
palzontology, though much affected by the prevailing belief—that 
every species, ancient and modern, was a distinct and separate 
creation. This belief still lingers in the minds of some, and the 
unequal value of specific names as a means of differentiation may 
perhaps tend to foster the idea by increasing the apparent imper- 
fection of the geologic record. Our object, therefore, in dealing 
with the Corallian Gasteropoda should be, after a careful description 
of such forms as seem entitled to the denomination of species, to 
dwell especially upon their distribution and representatives or 
relatives in other districts or in other beds in the same district. 
This method may be of service in arriving at an understanding as to 
the physical conditions and life history of the period, without in any 
degree conflicting with the more important biological work of other 
authors. 
(Zo be continued.) 
IJ.—Txx Svspivisions oF THE CHALK. 
By A. J. Juxzs-Browne, B.A., F.G.S. 
[Read before the Geological Society of Norwich, Feb. 3rd, 1880; and communicated 
by permission of the Director-General of the Geological Survey. ] 
A Nee earliest attempt to describe the component beds of the 
English Chalk was made by W. Phillips in 1819: this is his 
well-known account of the cliffs between Dover and Folkestone, 
which is reproduced in Conybeare and Phillips’ Geology (1822). 
He recognizes four divisions as follows :— 
1. The Chalk, with numerous flints. 
2. The Chalk, with few flints. 
38. The Chalk, without flints. 
4, The Grey Chalk or Chalk Marl. 
Samuel Woodward published his Geology of Norfolk in 1833, and 
his classification is very similar, viz.— 
1. Upper Chalk, with many flints. 
2. Medial Chalk, with few flints. ? 
38. Lower Chalk, without flints. 
4. Chalk Marl. 
The extent of ground occupied by each of these divisions is indi- 
cated in the geological map, but the boundary-lines are stated to be 
only approximately correct, and it is evident that they are so. It 
would therefore be difficult to say how far the divisions proposed by 
Phillips and Woodward are respectively identical, but it is obvious 
that the same basis of classification is adopted by both. The 
