ERITISII ASSOCIATION MEETING AT CAMBHTDGE. 



457 



and the red sandstones of Soutli Wales, although each deposited within 

 the same great period, are not strictly ('onteni])oraneons, but were formed 

 at different parts of the period. Oi- it is ])ossible the red sandstone scrits 

 of South Wales is not a continuous series ; that the lower part of it, at 

 all events, is older than any of the Devon scries, while the upper part 

 may he nev^ cr than much of that series."* 



That some — that much — diversity of opinion should exist, respecting the 

 time relations of the two systems of rocks now under notice, is what 

 might be expected when their lithological and pala3ontological dissimi- 

 larities a,re remembered; the northern beds are eminently arenaceous, whilst 

 those in the south are almost exclusively argillaceous or calcareous ; the 

 former teem with fossil fish, and the latter wath the exuvite of mollus- 

 cous and radiate animals ; but, according to our fossil registers, Scot- 

 land does not yield the shells, corals, or sponges so abundant in De- 

 vonshire ; nor are the ichthyolites of the former found in the latter area : 

 they have no organic remains in common. 



It will doubtless be remembered, however, that in his ' Pala30zoic .Fossils 

 of Cornwall, Devon, and West Somerset,' Professor Phillips has figured 

 and described as a scale of Holoplyclirus, a fossil found in the slates of 

 Meadfoot, near Torquay, in South Devon.f It would seem that this iden- 

 tification has not been considered perfectly rehable, since the fossil has 

 not found a place in subsequent works on the Devonshire beds, or in Pro- 

 fessor Morris's 'Catalogue of British Fossils.' 



This dissimilarity of the organisms of two not very widely separated, 

 and, as has been supposed, coiitemporary sets of deposits, is, to say tlie 

 least, very remarkable. The mineral and mechanical characters of the Old 

 Hed rocks may sufficiently explain the absence, in them, of mollusks, and 

 other dwellers at the sea-bottom ; but there seems no satisfactory mode of 

 accounting for the non-appearance of fishes in the slates and limestones of 

 Devon and Cornwall. Various solutions of the problem have been at- 

 tempted. We are asked by one to suppose that some geographical diffi- 

 culty or barrier separated the two areas and prevented the migration and 

 mingling of their inhabitants ; whilst another suggests that the Old Ped 

 fish were probably at home in fresh water only, and ought not to be looked 

 for in beds so decidedly marine as those of Devon ancl Cornwall. 



The interesting and important discovery, by Sir li. T. Murchison, of the 

 intermixture, in the same Devonian bed in Eussia, of the fish of the Upper 

 and Middle Old Ped of Scotland with the shells of Devonshire, J leaves 

 the ditBculty untouched ; nor does it appear that the synchronism of tlie 

 representative beds in Britain necessarily flovi s from it. It proves, of 

 course, that the fish and shells lived at one and the same time in Pussian, 

 not that they did so in British, waters. We may have an example, 

 here, of the distinction between geological conie)))j)omnciti/ and synchrony, 

 so ably pointed out, on a recent occasion, by Professor KuxU\y.§ It is 

 possible, for instai.ce, that the fish connncnced existence before tlie shells; 

 that tlic}^ appeared in Scotland long before their descent upon Pussia ; that 

 slowly changing conditions compelled them tardily to abandon their ear- 

 lier home for a more congenial one ; and that, on their arrival, they found 

 there the invertebrate tribes which subsequently migrated to where the 

 foundations of the future Devon and Cornwall were being laid. 



Be this as it may, some geologists, recognizing the synchronism of the 



* 'Manual of Gcolocry,' 2ii(l edit. (1802), p. 492. 

 t Tal. Fossils, j)l. 57, 250, p. 133. 

 + ' Siliiria,' 3r(l edit., p.' 382. 



§ Aiuiivcrsary Address, Quait. .loui-ii. Cool. Soc., vol. wii. part 2. 

 VOL. V. 3 N 



