THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
151 
is concretionary, and quite oolitic in places, the grains being 
flattish and elliptical in shape; a few grey micaceous patches, 
also many small pebbles, and some larger concretions are 
present. This description is quite sufficient for the same 
bed as it exists at Gay ton, some five miles south-west of 
Northampton, almost exactly on the line of strike. 
At Milton , to the east of this line, and Bughrook to the 
west, the bed is a little different in character. At the former 
place the oolitic character is not noticeable, whereas at the 
latter it is very pronounced; also fossils seem more abundant 
as we go westward, because there is less matrix. 
At Daventry, where the bed is superficial, and Staverton, 
where it has been long exposed, the green colour is not to 
be observed, partly owing to oxidation and partly because at 
these places it is almost entirely composed of fossils. The 
situation of these two sections is almost exactly on the line 
of strike, and near the westerly limits of the Middle Lias 
outcrop. If the lines connecting Northampton and Gayton 
and Daventry and Staverton respectively be produced, it will 
be seen that Chalcomb lies nearly midway between them, and 
the bed there possesses intermediate characters. 
At Chalcomb the bed has the same mottled appearance 
that it has at Northampton, though the colour is much less 
decided ; also it is more fossiliferous, though less so than the 
same bed at Staverton. Some portions of the bed at 
Chalcomb are exceedingly pretty ; they are highly vesicular, 
the cavities being filled in partially or entirely with calcspar, 
which shows up well against the other portion of the stone — 
red in these cases. Several good springs issue from the base 
of this bed hereabouts, and no doubt running water has 
effected the change above referred to. An experiment in the 
laboratory with some of the stone from Northampton showed 
that the green portion was mostly soluble in hydrochloric 
acid, with effervescence, the ochreous portions being much 
less soluble. 
The bed near Northampton seems to be characterised by 
very large specimens of Pecten liasinus, and everywhere by 
small pebbles. A little iron pyrites was found in one or two 
specimens, which accounted for the sulphurous odour emitted 
when they were struck by the hammer. The thickness seems 
to decrease in a northerly direction but to increase eastwards. 
At Chalcomb it is probably 2ft., Staverton 1ft. 4in., Daventry 
lft. Sin., Northampton between 3ft. and 4ft. 
Fossils. 
Ichthyosaurus tooth (?) ... Staverton. 
Fish remains, vertebra and teeth of small Jish, dc. Staverton 
and Northampton, 
