John Randall — Geology of Linley Valley. 497 



were, of the molluscs of the time to keep their ground in the waters 

 covering this area — there would appear to be few other traces of 

 animal life than the remains of fishes, and these chiefly in the Corn- 

 stones, or limestones, associated with the red or variegated marls and 

 sandstones. Fishes could readily swim freely without injuiy in the 

 waters from which the peroxide of iron was thrown down, so long 

 as they did not disturb the substance at the bottom, while at the 

 same time molluscs would be incapable of crawling upon or living 

 in the sand or mud intermingled with the peroxide, as we have found 

 by experiments ; so that at any intervals when the waters might be 

 relieved by deposit from their load of mechanically suspended per- 

 oxide of iron, the fish could readily enter the area exposed to this 

 kind of red accumulation." Seeing that there is no break or 

 unconformity in these two sets of rocks, the Upper Ludlow and the 

 Old JRed rocks, but that the physical passage from one to the other by 

 these stratigraphical beds is uniform and complete, it is difficult to 

 account for the life break which takes place in passing from one for- 

 mation to the other, excepting on the ground that great changes in 

 the relative positions of land and water must have taken place, 

 causing the marine condition of an extensive area most probably to 

 have become one of fresh-water, seeing that the remains found 

 belong to the latter, and that marine forms did not live on beyond 

 the limits of these passage-beds. The marine Silurian sea must have 

 been slowly and gradually changing at the time these beds were 

 formed by elevations and oscillations of the land over an oval basin- 

 shaped region, extending from this northern point to Haverford-West 

 and Milford Haven, in South Wales, on the one side, and along the 

 Abberley and Malvern ranges, and the eastern margin of the Bristol 

 Coal-field on the other. Over this large area during long intervals 

 of time fresh-water conditions, estuarine or lacustrine, with slow but 

 continuous elevation of land, are supposed to have continued, for no 

 form of invertebrate life appears to have lived on beyond these beds,^ 

 which form the confines of the two systems. 



Clearly, an entire change took place in the marine fauna as we 

 follow through this series of beds from the Ludlow Limestone 

 to the conformable Lower Old Eed Sandstone, when the few fish 

 and Crustacea common to them almost, if not entirely, disappeared ; 

 for the vast accumulation of these sandstones in this district marks 

 an epoch and an era almost barren of life ; only two or three species, 

 and these land and fresh- water, being found, and they only in the 

 upper portions of the Old Eed. 



In supposing this section of Old Red Sandstone to have been piled 

 up under fresh-water rather than marine conditions, I have adopted 

 the views of Mr. Robert Etheridge, F.R.S., who holds that an exten- 

 sive coast-line or barrier existed south of the Memdip Hills, separat- 

 ing it from the fossiliferous marine Devonians, which he divides into 

 a middle, lower, and upper series. 



1 We assume the autlior means life in this particular area ; he does not of course 

 imply that no form of invertebrate life passed from tlie scene of the older into that 

 of the newer deposit. —Edit. Geol. Mag. 



VOL. X. — xo. cxiii. 3i 



