C. LAPWORTH ON THE MOEEAT SEEIES. 345 



by. He did not know the district, but the interpretation put upon 

 the section by Mr. Lapworth agreed very well with what we should 

 expect from the manner in which the May-Hill beds of S. Wales die 

 out and, where we should expect them in 1ST. Wales, the Corwen 

 Grits, Tarannon Shales, and black bands come in, succeeded by the 

 Denbigh Mags ; and then, nearer Moffat, in the Lake-district, an 

 almost exactly similar series, but more like the Moffat section, with 

 abundant fossils in the black bands similar to those associated with 

 the Tarannon Shales of N". Wales. These, which were the Grapto- 

 lithic Mudstones of the Lake-district, he recognized in Mr. Lap- 

 worth's Birkhill group. To complete the story, in Scandinavia, on 

 the other side of Mr. Lapworth's sections, we have the whole series 

 represented by from 250 to 1000 feet; yet the details are very 

 similar. Having, by a question, obtained from Mr. Lapworth the 

 opinion that the strongest break in the Moffat series was at the base 

 of the Birkhill group, which, by the association of fossils elsewhere, 

 seemed to be the equivalent of the Lower Llandovery, he pointed 

 out that we have here additional evidence in favour of bracketing 

 the Upper and Lower Llandovery together, and taking them as the 

 base of the Silurian. 



The Author regretted that in the limited time at his disposal he 

 had been unable to lay before the meeting more than a small fraction 

 of the physical and palseontological evidence upon which his con- 

 clusions were founded. If, however, it was conceded that the 

 typical sections had been correctly interpreted, and that the succes- 

 sion of organic forms therein was in precise agreement with that in 

 England and Europe, much of the remainder followed almost of 

 necessity. 



In answer to Prof. Ramsay, the author replied that the general 

 theory of the succession among the South Scottish Silurians adopted 

 by the Scotch Survey was dependent solely upon broad generaliza- 

 tions from the apparent order of superposition, in districts where it 

 is admitted that in any single visible section it is impossible to be 

 certain whether we are ascending or descending in the order of the 

 beds. It leaves all the anomalies of the Scotch beds unexplained, 

 and is crowded with insuperable difficulties. It places in a single 

 subdivision of the Llandeilo formation a thickness of comparatively 

 barren beds almost equal to that of the whole thickness of the fossili- 

 ferous Silurian elsewhere. The black beds near the supposed base of 

 this immense formation swarm with Graptolites peculiar to the 

 Llandovery rocks of other countries. Thousands of feet higher in 

 the succession these wholly disappear, and few are met with but 

 peculiar Bala forms ; while, at the very summit of the formation, 

 the only survivors are either strictly Llandeilo forms, or have come 

 up from the Arenig itself. 



With regard to the two supposed unconformities alluded to, it 

 was admitted by the Professor himself that no physical proofs were 

 forthcoming in support of them. In fact the supporters of this 

 theory have been driven to adopt these breaks in order that they 

 may not be compelled to relinquish their fundamental hypothesis 

 Q.J.G.S. No. 134. 2 a 



