A HISTORY OF NORTHAMPTONSHIRE Any of the hard beds may yield water, but the only ones that can be fairly well relied upon to do so, and that give permanent springs within the district, are those marked thus *. The Junction bed. No. 7, is seldom to be seen ; the most interesting exposure that has occurred was near to Welton Station.' Beds included under 6 may be examined in the deep valleys around Catesby and Hellidon ; beds 3 to 5 near to Staverton and Byfield, etc. The Marlstone rock-bed, No. i, may be found over much of the area shown as Middle Lias on the map ; it is by far the most important bed, having been worked for ironstone in the south-western parts of the county, near Kings Sutton, and for building stone and road metal almost everywhere where it occurs near to the surface. The Transition Bed At or near the close of the Middle Lias period there appears to have been a pause in the terrestrial movements we have chronicled in previous pages, during which time little or no sedimentation took place, for attrition of the rock-bed itself may have yielded the small thickness of grey marl usually found resting upon it. The striking similarity in character, thickness, and fossil contents of the Transition bed over a large part of Northamptonshire and some neighbouring counties, indicates uniformity of conditions, including depth, hence a few pages back we took this horizon as a datum for calculating subsequent earth movements. The time taken up by the period we are considering was no doubt a fairly long one, for the fauna of the bed is a mixture indicating a decline of Middle Lias forms and an influx of Upper Lias ones, hence the term ' Transition Bed ' given to it by Mr. E. A. Walford.^ Ammonites acutus is characteristic, and several of the interesting gasteropods found in it might be so regarded for this district. The Upper Lias Before the Transition period much or the whole of Northampton- shire was embraced in the north-westerly rising area, after it in the sink- ing (south-easterly or general ?) area. Then followed, on a smaller scale, a remarkable repetition of Lower and Middle Lias phenomena. As the near land disappeared, and the shore line receded, in succession were formed paper shales with much vegetable matter, and fine-grained fish and insect limestones, then calcareous clays with argillaceous limestones, (but only two or three) ; next purer clays with isolated cement stones. Towards the close (corresponding to the change from Lower to Middle Lias, p. 11) we find a layer of water-worn nodules and rolled fossils, some covered with ostrea or serpu/ce, followed by micaceous sandy clays containing an entirely new fauna mixed with the old, and in certain ' W. D. Crick and C. Davies Sherborn, ' On some Liassic Foraminifera from North- amptonshire,' Journ. North. Nat. Hist. Sac, vol. vi. p. 2o8.
- Edwin A. Walford, ' On some Middle and Upper Lias Beds in the Neighbourhood of
Banbury,' Proc. IVarw. Nat. and Arch. Field Club (1878). 12
