LOWER CHALK —ISLE OF WIGHT. 
81 
local base of the Chalk. Am. [Schl.] rostratus, on the other hand, has 
never yet been found (underived) in any bed which could be referred 
to the Chloritic Marl, and it is very rarely found in the higher beds 
of the G-reensand. The species which we have found to be the 
most reliable guide is Stauronema Garteri. The range of this species 
appears to be very limited ; it is common in the bed which has 
always been regarded by the Geological Survey as typical Chloritic 
Marl. It occurs up to 14 feet above this bed at Culver, and has 
been found by Mr. Rhodes and Mr. J. B. Hue in the beds which 
underlie the phosphatic bed (those numbered 3 and 4 by us), and 
Mr. Hue has found a specimen in the still lower bed (2) near Ventnor. 
But it has never been found below this. So far, therefore, as Stauro¬ 
nema Garteri may be relied upon, its evidence leads us to include this 
lower bed with the Chloritic Marl, and to regard it as the basement 
bed of the Lower Chalk. 
It is exactly this point which makes the enquiry of importance, 
for otherwise it might seem a trivial matter whether a foot or so 
of material were or were not classed under the head of Chloritic 
Marl; but when we remember that if it is so classed all the fossils 
it contains will have to be regarded as Lower Chalk fossils, and will 
have to be excluded from the list of Selbornian fossils, then it will 
be seen that no pains should be spared in collecting and weighing 
the evidence. 
During the examination of the sections in 1897 and 1898 several 
important facts were observed which have enabled us to correlate 
the sections seen at different localities with one another. In the 
first place it was noticed that in every section, at what appeared to 
be the same horizon, there was an appreciable change in the charac¬ 
ter and colour of the rock-material; the bed below this plane being 
light grey or yellowish green, and less glauconitic, that above it 
being greyish-green and very glauconitic ; moreover, the lower 
bed is generally piped and mottled with the darker material, as if 
filled with holes and borings which had been made in the lower bed 
before the deposition of the upper bed. This recalls the relation of 
the zone of Stauronema Garteri at Folkestone to the underlying 
Gault, though the materials do not contrast so markedly as at 
Folkestone. Moreover on the western side of the island there are 
indications of current erosion at the same horizon, the bored surface 
being also an uneven surface with hollows which are sometimes 
15 to 18 inches in maximum depth. 
On a more recent visit (May, 1898) Mr. Hill paid special atten¬ 
tion to the beds at this horizon, and examined the large fallen masses 
on the shore between Ventnor and Rocken End. Starting from 
the Ventnor section, which was published by us in 1896,* he found 
that the bed which was then numbered 3 could be recognised in all 
the exposures to the westward. This is a nodule-bed, enclosing 
lumps of hard fine-grained calcareous sandstone, which have been 
4219. 
See Quart. Journ. Geol. Soc., Vol. lii. p. 105. 
F 
