320 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 22, 



was at work at the time the shales in which tliey are imbedded 

 were deposited, and before the overlying stratum was formed. Above 

 this bed of shale we have a thin band of dark-grey stone (No. 19), 

 varying from 1 inch to 3 inches in thickness, containing Pecten 

 Valoniensis, Avicula contorta, ScMzodus doacinus, Modiola minima, 

 and what appear to be worm-tracks, or casts of the traces of 

 crawling mollusks or crustaceans. This stone band, the only one in 

 the series where (owing to the indefatigable researches of my friend 

 Mr. Waugh, of the Great l^orthern staff, to whom I owe the accurate 

 diagrams accompanying this paper) I have met with the well-known 

 Pecten Valoniensis, so common in other similar localities, lies just 

 above the septarian nodules in the shales below, sometimes reclining 

 on them ; and where these bodies occur, the stone assumes, as just 

 stated, a dome- shaped curve, being thinnest on the raised summit of 

 the nodules, and thickest in the intervening spaces, while, resting 

 on the stone, in the hollows between the swellings caused by the 

 septaria, he veins of black fibrous gypsum similar to those described 

 in the shale-bed (No. 18) below. Kext in order comes another 

 bed of black fissile shale (No. 20) from 1 foot to 3 feet thick, similar in 

 character to all the others, and forming the highest bed of the series 

 in this locality, aE. above it being, as far as the railway- cutting 

 extends, denuded and worn down by the drift, which, at a distance 

 of about 90 yards above Lea-bridge, suddenly cuts clean through all 

 the intervening beds down to the main stone band (No. 9), crushing 

 and distorting the various strata, and making the smooth slippery 

 surfaces of the shales appear as if they had been polished*. At 

 this point also the strata from beneath rise again, and the grey 

 Keuper marl becomes visible at the base of the cutting, showing the 

 form of the Ehsetic beds in this locality to be that of a shallow 

 synclinal basin. That higher beds of the series existed in these 

 parts is evident from the clean-fractured uneven fragments of 

 White Lias which are found in the overlying drift, containing Mya- 

 cites musculoides, Cardium Bhoeticum, and other fossils, with the old 

 perforated tubes of boring mollusks, the latter pointing, as Mr. 

 Moore, in his paper already cited, observes, to a quiet period of de- 

 position, when such delicate operations could take effect. One of 

 the most remarkable characteristics of the Gainsborough beds is the 

 presence of the immense quantity of iron pyrites found in the dif- 

 ferent strata, all of them, whether shale or stone, being literally 

 filled with this mineral. In the shale it occurs as a simple cube, or 

 number of cubes, and in the stone as a bright metallic layer or 

 streak ; and so filled is the entire series with this substance, that I 

 have seen, after heavy rains, the sides of the cutting in places stained 

 yellow, as if with rust, completely effacing the lines of bedding. 

 How far the surface-limits of this Ehsetic tract extend it is not easy 

 to ascertain with exactness; judging, however, from the contour of the 

 surrounding land, an estimate of its size and position may, I think, 



^ Since this paper was read, I have discovered, in the old undisturbed parts of 

 the cu.tting, traces of strata in sitti belonging to the Eh£etic series higher than 

 those described. 



