TRANSACTIONS OF THE SECTIONS. 5.3 



slate 50 per cent., and of the yellow sandstone 48 per cent., as already mentioned, 

 were common to the British mountain limestone ; and if the entire series were taken, 

 it appeared that out of 430 species which had been described as occurring in that 

 series, 287, or 67 per cent., were common to the mountain limestone of Ireland. 

 Hence he concluded, that the mountain limestones of Great Britain and Ireland be- 

 longed to the same geological suite, though the Irish series generally, and particularly 

 the lower members, contained a great number of species, which had not hitherto been 

 discovered in the British. From the foregoing data there appeared to be a greater 

 affinity between the upper limestone of Ireland and the British mountain limestone, 

 than between it and the other members of the Irish series. Again, the upper lime- 

 stone of Ireland contained only 16 species of fossils, or 8 per cent., which were com- 

 mon to North Devon, while the calp contained 43, or 16 per cent., the lower lime- 

 stone 39, or 10 per cent., the carboniferous slate 65, or 24 per cent., and the yellow 

 sandstone 35, or 29 per cent., in common with the same series. Thus there appeared 

 to be a nearly regular gradation from the upper portion of the mountain limestone 

 of Ireland into the upper Devonian; and although, owing to the predominance of 

 ordinary mountain limestone fossils, the per-centage is not considerable even in the 

 lower members, yet by reference to the table of results it appeared, that out of 122 

 species of fossils from North Devon, 80, or 65§ per cent., occurred in the mountain 

 limestone of Ireland; and hence Mr. Griffith concluded, that hardly a doubt could 

 be entertained as to the propriety of attaching the fossils of North Devon to the 

 mountain limestone series of Ireland. He considered this a startling result, and one 

 which could not have been foreseen from our previous knowledge of the fossils be- 

 longing to the British mountain limestone, which contained only 22 species common 

 to North Devon, and made the conclusion of some distinguished geologists as to the 

 separation of the Devonian system from the mountain limestone, perfectly legitimate, 

 even as regarded the northern portion of the district. Mr. Griffith observed, that this 

 comparison between the mountain limestone and the Devonian fossils had been con- 

 fined to those of North Devon. By a similar comparison with South Devon, the re- 

 sults were essentially different, inasmuch as out of 257 species of fossils obtained from 

 that district, only 94, or 36 per cent., were common to the mountain limestone of 

 Ireland, and 26, or nearly 1 1 per cent., to that of Great Britain, a result which led 

 to the conclusion, that the fossils of South Devon generally belonged to a different, 

 and, judging from the type of the fossils, to a more ancient period than those of North 

 Devon, though possibly a portion adjoining the culm series might eventually be found 

 to correspond with the period of North Devon. The fossils of North Devon were 

 given in these tables as described by Mr. Sowerby, Mr. L,onsdale and Mr. Phillips, and 

 those of the mountain limestone of Great Britain, by Mr. Sowerby and Mr. Phillips. 

 In regard to the fossils of the mountain limestone of Ireland, nearly the whole of the 

 fossils named in the table had been obtained by, and were in the collection of, the 

 author; of the 568 species which it contained, 166 were supposed to be new by Mr. 

 M'Coy of Dublin, who had examined and named them. Mr. Griffith stated, that the 

 collection also contained upwards of 100 additional new species, which were under 

 examination, including several species of Entomostraca, from the calp of Bundoran, 

 in the county of Donegal, the lower limestone at Armagh, and the carboniferous slate 

 at Howth, in the county of Dublin; numerous remains of fossil fish had also been 

 collected, but they had not yet been sufficiently examined to be named and intro- 

 duced in the catalogue. Mr. Griffith observed, in conclusion, that these investiga- 

 tions must still be considered as in their infancy ; the collection from the upper lime- 

 stone was particularly deficient, which had arisen from the circumstance of the di- 

 strict containing the best development of that member of the series being situated near 

 the summits of elevated crags, where no quarries had been opened ; and every geo- 

 logist was aware of the difficulty of collecting a good suite of fossils under such 

 circumstances. 



Notice on the distinction between the Striated Surface of Rocks and Parallel 

 Undulations dependent on Original Structure. By R. I. Murchison, 

 Pres. G.S. 



The President called attention to an interesting notice just published in the Scots- 

 man newspaper and sent to him by the author, Mr. MacLaren, "On the Striated 



