Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/527

1870.] SHARP NORTHAMPTONSHIRE OOLITES. 361 Among the points of interest in this section are : — 1. The " Dirt Bed" (no. 3), which is of very similar character to the " shaly " bed at Tinkler's pit at Stamford, noticed by Professor Morris in the typical section of the Stamford Oolites given in a note in his paper in the Journal for November 1853. This bed is evidence of a comparatively brief but marked change in the local conditions during the period of its deposit.

2. The " Paving Beds " (nos. 7 & 8) : these exhibit on the joint-surfaces the peculiarity of the fossils being thrown out into strong relief by the partial solution of the softer calcareous matrix, probably by the action of water charged with carbonic acid.

3. The zone of Ostrea Sowerbyi in the " Bottom Jubs." This Ostrea occurs in some sections in great abundance in the underlying clay B.

As to the fossils contained in these beds, I would particularly refer to the cast of a large smooth Ammonite, some 15 inches in diameter, formerly in Miss Baker's collection (now in the British Museum, and as yet, I believe, undescribed*, two similar Ammonites having been obtained by me from the Great Oolite at Blisworth) — to a remarkable fish-jaw, I believe of Lepidotus — to the great number of fish-palates, some probably of Strophodus magnus and S. subreticulatus, and teeth of Saurians — to the abundance of large Pholadomyoe, Pinna ampla, Naticoe, Nautilus Baberi, and N. subtruncatus, Clypeus Mulleri and C. Plotii — and to the characteristic zone of Rhynchonella concinna at the base.

The section of the pit marked b shows a continuation of the beds of pits a ; and it would be merely repetition to give it in detail. In this pit, however, the Rhynconella zone at the base is usually accessible, and is sometimes seen to pass into the underlying blue clay B.

The same fossil forms which are abundant in pits a abound also in pit b. Here was found the remarkable Pandanaceous fruit figured and described by Mr. Carruthers, F.L.S., F.G.S., of the British Museum, in the Geological Magazine, April, 1868, under the name of Kaidacarpum ooliticum.

The chief characteristic of the Buttock's Booth pit (c), which exposes a section of the lower beds only of pits a and b, is an abundance of fruit of Carpolithes, fish-palates and saurian teeth, and remains of crustaceans of two varieties of Eryma, near to E. elegans, Opp. Osseous fragments of Teleosaurus have more than once been found here.

Underlying the limestone is a bed of blue or dark grey clay, B, of a thickness, ascertained by well-sinking, of 14 feet, which is also to be classed as Great Oolite. The junction of the limestone with, and indeed its passage down into, this clay, is to be seen in the bottom of the pit b. Here the zone of Rhynchonella concinna and Modiola imbricata extends into the Clay itself. The junction is also

in the British Museum and identified it as an old and smooth individual of Ammonites gracilis, Buckman.
 * Since the reading of this Memoir, Mr. Etheridge has examined the Ammonite

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