232 PROCEEBiNGS OP THE aEOLOGiCAL SOCIETY. [March G, 



could l)c 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 pre- 

 sented 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. Peestwich 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 Oarditt 

 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 Graptolitidaj 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 re- 

 garded the Quebec area as that in which these forms had originated. 



Prof. Eajisat 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 Eirth 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 Melllss, Esq., C.E., 90 Richmond Road, Westbourne 

 Park, W., and Thomas Mellard Reade, Esq., C.E., of Heath House, 

 Blundellsands, Liverpool, Avere elected Fellows of the Society. 



The following communications were read :— 



