506 
THE CRETACEOUS ROCKS OF BRITAIN. 
calcitic crystals, so that the contrast between them and the darker 
tint of the calcareous matrix, in which they are embedded, brings 
them into strong relief when thin sections of the rock are viewed 
under the microscope (see Plate VIII, Fig. 1). Large G-lobigerina and 
a few Textularia also occur, the former being fairly numerous in 
some specimens, but as a whole their proportion to the mass of the 
rock is not great. Large fragments of Inoceramus-sh ell are abun¬ 
dant, and serve also to distinguish this zone from all others in 
the chalk, but their number diminishes gradually towards the 
summit of the zone. 
The regular character of this zone is, however, broken in Devon¬ 
shire by the well-known Beer Freestone, and by other, but less 
important, rocky beds which occur above or below this stone. 
The Beer Freestone consists almost entirely of coarse calcareous 
shell-fragments. Some of these are prisms of Inoceramus , and 
others are plates of Echinoderms, but the larger number are frag¬ 
ments of irregular shape, which show a peculiar perforated or 
cellular-like structure. There are no Spheres and very few 
Foraminifera, but the interstices between the shell-fragments are 
filled with amorphous calcareous material, the wdiole being in 
a semi-crystalline condition. The rock is therefore a shell lime¬ 
stone, and can hardly be called a “ chalk.” 
The basal part of the freestone has a similar structure, consisting 
almost entirely of perforated shell-fragments . Our section con¬ 
tains also three or four large glauconitic grains. 
Since the above was written, Dr. G-. J. Hinde has cut slides 
from samples of the Beer and Sutton freestones sent him by Mr. 
Jukes-Browne. These show that both freestones have the same 
constituents and a similar structure, but that Foraminifera are 
rather more abundant in the Sutton stone. Dr. Hinde writes: 
“ From further study of the puzzling reticulate structure, I think 
that some at least may be due to the excavations of boring 
organisms in fragments of Inoceramus-sheW. The borings do not 
remind me of those of boring sponges, but there are various 
organisms capable of this work.”* 
Above the freestone is the “ cockly ” or “ roof bed,” as it is 
called by the workmen. This has a structure which recalls that 
of the Melbourn Bock. A thin section shows the rock to consist 
largely of coarse shell fragments, chiefly Inoceramus-prmms, and 
a few showing the cellular structure; large Globigerina are 
common. These coarse organic fragments are rather irregularly 
distributed, and in some places not very closely packed, the inter¬ 
vals being filled with amorphous calcareous paste, in which a gcod 
many spheres occur. The section contains also well-marked 
areas, which appear to be nodules of partly consolidated chalk 
of quite a different character. These nodules consist chiefly of 
amorphous paste, numerous spheres, and scarcely any shell frag¬ 
ments. Four or five large grains of glauconite occur in this 
section, and a single and somewhat large grain of quartz. 
