﻿1851.] BRODIE ON BASEMENT BEDS OF THE OOLITE. 211 



In my former paper in the Quarterly Geological Journal, the 

 group below the Pisolite was named the " Ammonite and Belemnite 

 bed*," for the preponderance of these shells, independent of any 

 other characters, distinguishes it from all others in the series. On the 

 whole, these genera are comparatively rare in any of the superior 

 divisions, and occur in greater or less profusion in the equivalent strata 

 at Painswick, Beacon Hill, Haresfield, Frocester, Wotton-under-Edge, 

 and Dundry. In all cases it may be also identified by the presence of 

 the small shining oolitic grains, cemented by a brown or white calca- 

 reous paste. The remains of Fish appear to be merely local, for I have 

 not observed them in any of the localities above-mentioned. With 

 the exception of a few large Palatal teeth in the Pisolite, any traces 

 of Fish are seldom met with in the Inferior Oolite of Gloucestershire, 

 and their abundance in the present instance is a remarkable exception 

 to the general rule. The bones, scales, coprolites, and teeth are very 

 minute, rolled, and fragmentary, but in sufficient numbers to form a 

 kind of Bone-bed, and probably belong to more than one species of 

 Fish, and I have only noticed one which could be ascribed to Saurians. 

 Teeth are not common ; the few which have been discovered were 

 pronounced by Sir P. Egerton to belong to a species of Hybodus. 

 The great profusion of certain genera of Cephalopods, such as Am- 

 monites, Nautili, and Belemnites, indicates a deep sea, which 

 evidently became shallower during the deposition of the shelly free- 

 stone, and even in some degree before the Pisolite ; an inference 

 which may be drawn from the presence of Lithodomi. The evidence 

 afforded by the occurrence of a boring Mollusk is that of partial ele- 

 vation and repose ; but, as Ammonites and Belemnites are again 

 found a little higher up, there must have been another local subsi- 

 dence ; after which, and before the formation of the freestone, the 

 sea would seem to have been getting gradually shallower ; for the 

 general character both of the Pisolite and freestone points to an ocean 

 of less depth than that in which the Ammonite-bed f was deposited. 



It is a curious and interesting fact, that, in nearly every example, 

 the large fragmentary accumulations of the remains of Fish or Sau- 

 rians, commonly called "bone-beds," have taken place at the close of 

 one formation and the commencement of another ; and it is not per- 

 haps easy to assign a reason for this coincidence, although most of 

 these peculiar deposits are only local and not very extensive, the Lias 



* When I spoke of this stratum near Cheltenham (Quart. Journ. Geol. Soc. 

 vol. vi. p. 224, note) as being a diminished representative of its equivalent at Fro- 

 cester, I referred more especially to the increased thickness of the sands beneath, 

 which at Leckhampton are barely represented by three inches of sandy marl ; the 

 Ammonite and Belemnite bed itself being of uniform thickness, or nearly so, at 

 both those places, but expanding considerably at Wotton and Dundry. 



f Mr. J. C. Nesbitt has kindly examined some portions of this rock, and in- 

 forms me, that although he has not yet had leisure to make an accurate quantita- 

 tive analysis, yet, from qualitative experiments, he feels satisfied that the speci- 

 mens he examined, viz. a cast of a small Ammonite and hand-specimens with 

 many small fragments of bones, &c, from this basement-bed of the Inferior 

 Oolite, contain between 40 and 60 per cent, of phosphate of lime ; — in fact, that 

 the whole of the specimens are highly phosphatic. 



