Page:Quarterly Journal of the Geological Society of London, vol. 28.djvu/280

 could be no doubt of there being many species common to Europe, America, and Australia. This afforded strong evidence in favour of some such theory as that of migration. He cautioned observers to take careful notice of the manner in which Graptolites are presented in their matrix ; for, when seen from three different points of view, they exhibited such differences that three species might be made from one form of organism.

Mr. Gwyn Jeffreys mentioned the wide distribution of marine Hydrozoa by means of winds and currents, as illustrative of the history of Graptolites, the dispersion of which might have arisen from similar causes, and not from migration.

Mr. Prestwich commented on the uncertainty of our knowledge with regard to Graptolites, and consequently regarded speculation on the subject of their migration as premature. He instanced Cardita planicostata, which was formerly regarded as having originated in the Paris basin and come thence into England, but which had since been found in far earlier beds in Britain, so that the presumed course of its migration has been reversed.

Mr. Hicks remarked that the rocks referred by the author to the Upper Cambrian were in reality the lowest of the Silurian series, and that the Graptolitidae were exclusively a Silurian family.

Mr. HOPKINSON also made some remarks both on the distinction of different species of Graptolites and on their distribution. He regarded the Quebec area as that in which these forms had originated.

Prof. Ramsay commented on the great want of accord among those who had studied Graptolites, not only with regard to their structure, but to their distribution in different horizons. He thought that the suggestion of the author, as to modification of form during migration having taken place, seemed to throw some light on the subject. He could not regard two districts now only separated by the Solway Firth as constituting two geographical areas so distinct that the occurrence of the same species in both could with propriety be held to be due to migration. The phenomena in the other cases seemed to him quite as much in accordance with distribution from some common centre as with migration along any line connecting two spots where Graptolites are now found. He thought that the recurrence of some forms on different horizons in Cumberland was to be accounted for by the fact that the rocks which intervened between the Skiddaw Slates and the shales immediately above the Coniston Limestone were subaerial volcanic beds, on which, after submergence, newer muddy shales had been deposited.

March 6, 1872.

John Charles Melliss, Esq., C.E., 90 Richmond Road, Westbourne Park, W., and Thomas Mellard Reade, Esq., C.E., of Heath House, Blundellsands, Liverpool, were elected Fellows of the Society.

The following communications were read :—