149 
NOTE ON A LIASSIC CONCRETION. 
F. M. BURTON, F.L.S., F.G.S., 
Gainsborough. 
A RATHER remarkable concretion has been met with in a well 
which has recently been dug near a cottage at Blyton, a village 
about four miles from Gainsborough, situated on the Lower 
Lias. It consists of indurated clay, of a round disc-like shape 
as big as a small cart wheel, thinning off at the outer rim. 
When broken—and it had to be broken in pieces before it could 
be got out—the interior showed, in places near the circumference, 
vertical, fusiform cavities, 24 inches in height and about an inch 
apart, crowded on their surfaces with small, almost pulverulent, 
dog-tooth crystals of calcite, much stained with impurities, 
giving the mass somewhat the appearance of a huge ammonite 
with its septa.* In the middle portion the nodule is 44 inches 
thick, and judging from the curve of the outer rim, when entire 
it must have measured quite 3 feet in diameter, and probably 
more. Besides these vertical openings near the outer rim, there 
were many slits and cavities in the middle portion of the nodule, 
all lined with similar crystals, but on the outside of it there was 
no appearance of anything, the surface was homogeneous and 
smooth throughout. There is, of course, nothing unusual in 
this inner shrinkage and crystallisation, the cause of it is well 
known. Some organic remains which had collected (perhaps 
in a slight hollow of the matrix assuming its shape) had become 
enveloped in a crust of clay, and the organisms, shrinking first 
before the outer integument, secreted the crystals and caused 
the fissures which are found in it. 
Blyton lies on the fringe of the Am. angulatus zone of the 
Lower Lias, and on examining the heap thrown out in digging 
the well I found an ordinary septarian nodule, so frequent in 
these deposits, with some thin pieces of hardened limestone 
containing worn fragments of Gryphea and other fossils. The 
well is 14 feet deep, and as the lowest zone of the Lower Lias, 
Am. planorbis, occurs in this neighbourhood at about the same 
horizon—being found near Corringham, Springthorpe, Lea, 
Gate Burton, and Marton—this concretion may belong to that 
zone which, in some places, shows signs of having been deposited 
a 
* The specimen sent to us is certainly remarkable for the regularity of 
shape, and distance apart, of the lenticular cracks, which are, of course, 
fusiform in section.—EDs. 
1907 April 1. 
