292 ON THE ZONAL STRATIFICATION OF THE
lumps of grey or dark glauconitic sandstones so frequently met
with) are at present of unknown origin, as although M. Omalius
d'Halloy noticed the tendency of the glauconitic grains to form
nodular concretions, they do not seem to have attracted the
notice of the Belgian geologists. Glauconite, like manganese,
seems to have a tendency to envelope or segregate round some
foreign substance, hence the great variety of organisms found
in these nodules.
The Rev. H. Canham, whose fine collection of box stones
is now in the Ipswich Museum, told me that about seventy-five
per cent. of them contained something, while only about one in
fifty were worth preserving. Selachian vertebrae, cancellated
bones and teeth of whale, and fish, are not uncommon, but
the interest centres in the mollusca, of which I know about 60
species, chiefly large forms, of which scarcely a dozen are recorded
in the "Sables Inferieurs" of Belgium—i.e. zones of Pecfuii-
culus pilosus, and of Panopaea menardi, never-the-less the abun-
dance of Isocardia lunulata in the box-stones tends to indicate
their contemporaneity. Amongst the new forms, are several
species of Sipho, Halia, Buccinum or allied form, Natica, Gibbula,
Architectonica, Nucula, Cardium, Venus, and others.
It may be noted that these organisms are very often
surrounded by the matrix and not showing at the sides, as if
the nodules had suffered very little from rolling about on the
sea bottom.
At Bawdsey the sandy lumps were often found in flat masses,
frequently with a flat bivalve on the surface. From their
quantity and wide distribution, the original deposit was
probably not far away.
I have in a brief notice of these stones (Journ. Ipswich
Field Club, 1911) had occasion to get together such informa-
tion concerning their contents as far as I found possible, and
shortly described a number of unfigured species from the
collections of the Rev. H. Canham, the Rev. C. Stanley, of
Bawdsey, and others. Mr. J. Reid Moir has since then kindly
given me several more from in and near Ipswich, and I have
also a number from the floor of the Coralline (Gedgravian) Crag
under examination. I hope to be allowed to lay a full account
with figures and all details of these exuviae before the Essex
Field Club later on.