Notices of Memoirs — Kilroe (^ McIIeiiry — Ordovickm Rocks. 173 



conjecture that the metaniorphic rocks of Galvva}', Mayo, etc., are 

 altered representatives of the Lower Sihirian or Ordovician rocks. 

 This, however, is not an obstacle, for a break, accompanied by 

 overfolding and possibly metamorphism of Lower Silurian strata, 

 has been proved to have occurred in Llandovery times, which 

 admitted of Wenlock or possibly Tarannon beds being unconformable 

 to unmetamorphosed Lower Silurian as well as to the metamorphio 

 group. All this happened prior to a second violent disturbance 

 and overfolding whicli accompanied the metamorphism of Wenlock 

 strata already mentioned, and which occurred in Ludlow times. 



A comparison of the Lower Silurian series in the west of Ireland 

 with the metamorphic group of the same region and Donegal, shows 

 so strong a resemblance between them — as regai'ds the lithological 

 characters of individual members in their original form, their 

 order of succession, and certain peculiar coincidences of associated 

 sedimentary components, described in detail in the paper — that it 

 forms a creditable j^n'md /a cie argument for their correlation. 



One instance may here be mentioned. At Westport and Achill 

 Beg thick bands of fine conglomerate, associated with black slate, 

 occur as an integral part of the metamorphic group, while on the 

 south shore of Clew Bay thick bands of fine conglomerate — very- 

 similar in character to those in Achill Beg — occur in association 

 with black slate, which, though sufficiently crushed to justify their 

 inclusion by the original surveyors in the metamorphic ground, are 

 now known to be of Lower Silurian age, identical with rocks of 

 this age in Clare Island. 



The chief objection to ascribing the metamorphic rocks of Mayo and 

 Galwaj' to the Lower Silurian age has been the present difi'erence 

 of condition between them and the fossil-bearing Lower Silurian 

 rocks of the adjoining area. This difference seems to us explicable 

 by conceiving that the great dislocation which occurred in Llandovery 

 times, and occasioned an inversion of strata by overfolding at Salrock 

 between the Killaries, carried unmetamorphosed Lower Silurian 

 rocks about Leenane against and over rocks of, say, the same age, 

 near Leenane, which had undergone metamorphism in connection 

 with granitic intrusions. These may be seen in the vicinity of 

 Kylemore. Unfortunately the great zone of break is now concealed 

 by newer strata, and further is obscured and complicated by post- 

 Ludlow faults. 



III. — The Glossoptekis Flora of Australia. By E. A. N. Arbkr, 

 B.A., Trinity College, Cambridge.^ 



THE Glossopteris flora is one of the most remarkable and widely 

 distributed of fossil floras. Typical members, such as the fern- 

 like plants Glossopteris and Gangamopteris, with the Equisetalean 

 genus Phyllotheca, occur in rocks of Permo-Carboniferous age in 

 India, Australia, South Africa, and South America, pointing to the 



^ Read before the British Association, Section C (Geology), Glasgow, Sept., 1901. 

 See also Geol. Ma.g., Dec, 1901, p. 573. 



