56 Geological Society, 



the greater distance of these seas from each other than of the eastern 

 shores of England from the Faluns should he urged as an objection 

 to the inference that the crag and Faluns belong to one epoch, Mr. Lyell 

 ciills attention to the difference in the Testacea on the opposite sides of 

 the isthmuses of Suez and Panama, though these tracts are very incon- 

 siderable, both in height and breadth. That land existed in the imme- 

 diate neighbourhood of the Faluns, Mr. Lyell says, is proved, from 

 the occun-ence of the remains of terrestrial Mammalia, and of land and 

 freshwater shells, though they are of rare occurrence, compared with 

 the marine reliquiee ; and if it formed a barrier between the district oc- 

 cupied by the crag and that by the Faluns, the more northern charac- 

 ter of the crag fauna might be due to the sea in which it lived opening 

 to the north ; and in support of this opinion he alludes to the rapid trans- 

 ition in the southern hemisphere from a district possessing a mild and 

 equable climate. In which tropical forms of Testacea exist with others 

 common to high latitudes, to one of extreme cold. Lastly, Mr. Lyell 

 says, whatever speculations may be indulged, it is clear that the fos- 

 sUs of the crag and Faluns are almost entirely different from those of 

 the London clay and Paris basin ; that at least one-fifth of the fossil 

 shells, both in the crag and Faluns, are identical with recent species ; 

 that fifteen per cent, of the shells and corals of the Faluns are spe- 

 cifically identical with those of the Suffolk crag ; and that the sup- 

 posed difference of climate indicated to the Testacea and Polyparia 

 is by no means so great as some observers have supposed. Mr. Lyell 

 nevertheless does not attach such importance to the per-centage of 

 recent shells in the present state of knowledge of all the recent species, 

 as to deduce from this source alone a positive inference regarding 

 the precise agreement in age of the Faluns and the crag, merely 

 stating that both deposits are referable to the Miocene epoch ; and as 

 the red and coralline divisions of the Suffolk crag were not formed 

 at the same time, so he conceives there may have been shades of dif- 

 ference in the relative age of the Faluns and the crag. 



June 16. " Description of a Newer Pliocene Deposit at Stevenston, 

 and of Post-Tertiary Deposits at Stevenston and Largs, in the County 

 of Ayr," by the Rev. David Landsborough, and communicated by 

 •Tames Smith, Esq., F.G.S. 



The Newer Pliocene Deposit. — This stratum was discovered in 1839 

 in opening two coal-pits in the parish of Stevenston. After penetra- 

 ting from thirty to thirtj''-five feet of sand, a bed of blue clay, nine 

 feet thick, was passed through, and found to contain marine fossils 

 of the newer Pliocene epoch. All the species have been obtained in 

 other deposits of the same age in the basin of the Clyde, except two, 

 — Astorte horealis, which occurs in a fossil state in the crag and living 

 in the Arctic seas, and Asfai-te p7-opi7iquci , a new shell. Mr. Lands- 

 borough gives a list of the twenty-seven species collected by him, 

 nineteen of which are common in the adjoining seas, six are known 

 to exist in the Arctic seas, and two, Natica glaucinoides, a crag fossil, 

 and Astarte propiiiqtia, are believed to be extinct. 



Post-Tertiary Deposits. — The author prefixes to his account of 

 these beds a notice of the older formations in that part of Ayrshire. 



