By G. Poulett Scrope, Esq., M.P. 101 
shore, upon which clayey mud was dropped here and there by al- 
ternating currents—probably tidal. Many of these rippled sur- 
faces exactly resemble the sands left dry by the receding tide 
on our present coasts, and like them, are strewn with drifted 
shells and bits of wood, and the casts of Annelidz or sea-worms, 
and the tracks of crabs or other crustaceous animals. It is 
clear, therefore, that this entire range of hills at the time of the 
deposition of the oolitic beds that compose them, formed the shore 
of an island or continent lying to the westward of the sea in which 
these testacea lived. Some beds of the great oolite contain many 
fragments of coral, and appear formed by the breaking up of coral 
reefs by the waves. In some spots portions of the reef itself are 
seen to remain in place. The bones, teeth, palates, and scales of 
fishes are frequently met with in the oolite, especially in the Forest 
marble, as well as the-remains of some of those extraordinary | 
amphibious Saurians, or gigantic lizards, which abound in the Lias 
beneath, and of whose supposed forms representations are to be 
seen in the Crystal Palace gardens. A few fragments of bones 
have also been found in oolitic strata belonging, it is supposed, to 
mammiferous animals. And as this is a fact of considerable im- 
portance, if clearly made out, it is desirable that all such specimens 
as may be hereafter discovered, should be carefully examined by 
competent zoologists. 
Above and eastward of the Lower oolitic group we find a thick 
deposit of bluish clay, usuaJly called the Oxford clay. This forms 
the wide surface of the vale of the Avon from Westbury north- 
wards to Bradon forest, and thence eastward to that of the infant 
Thames at Cricklade and Castle Eaton. It has some hard fossilife- 
rous limestone beds near the bottom, where it rests on the Corn- 
brash, which from their occurring at Kelloways, near Chippenham, 
have been called the ‘Kelloways Rock.’ This is the bluish grey clay 
and shale, in some places 400 or 500 feet thick, which caused, and 
still causes, so much trouble to the contractors of the Great West- 
ern Railway, by the slips which take place in the cuttings through 
it, west of Wootton Bassett. It contains great numbers of ‘Cepha- 
lopoda’ of the genera Ammonite and Belemnite. Some specimens 
