Geological Society. 391 



species), and two species to a new genus, to which Mr. Matthew's 

 species Micmacca (?) plana may also be referred. 



All the trilobites are represented by detached portions or 

 fragments, often mixed indiscriminately, two or three species 

 together, in the separate bands of rock ; and the Author adduces in 

 some detail the evidence for correlating certain free-cheeks, thoracic 

 segments, and pygidia with the various head-shields, so that future 

 workers may clearly distinguish between that which is actual fact 

 and that which is a matter of inference. 



January 12th, 1910.— Prof. W. J. Sollas, LL.D., Sc.D., F.R.S., 

 President, in the Chair. 



The following communication was read : — 



' On the Igneous and Associated Sedimentary Rocks of the 

 Glensaul District (County Galway).' By Charles Irving Gardiner, 

 M.A., F.G.S., and Prof. Sidney Hugh Reynolds, M.A., F.G.S. ; 

 with a Palseontological Appendix by Frederick Richard Cow per 

 Reed, M.A., F.G.S. 



The general succession of the rocks of the Glensaul district is as 

 follows, in descending order : — 



3. ? Bala Beds. Conglomerates and Sandstones. 

 These beds have not been studied. 



2. Shangort and Tourniakeady Beds. Thickness 



(8) Calcareous gritty tuff of no great coarseness, sometimes in feet. 

 becoming so calcareous as to pass into fairly pure lime- 

 stone, enclosing also bands and patches of limestone- 

 breccia, and, more rarely, bands of highly fbssiliCerous 

 limestone which in some cases has been shattered by 

 earth-movements. 

 (7) Very coarse tuff or breccia, mainly composed of felsite- 

 fragments : associated with it are impersistent bands 



of fine tuff 750 



(6) Tuff, coarse and fine, with occasional patches of calcareous 

 beds, and at one point graptolitic beds indicating the 



zone of Didymograptus hirundo 150 



(5) Great felsite sill of Tonaglanna and Greenaun about 1100 



(4) Coarse grit 20 



(3) Gritty tuff varjing in thickness from 520 to 620 



(2) Coarse tuff or breccia, mainly composed of felsite-fragments 75 



(1) Fine banded tuff 55 



1. Mount Partry Beds. 



(4) Coarse grits 150 



(3) Fine grits and tuffs associated with black chert, graptolitio 



beds, and a prominent band of coarse tuff or breccia 

 about 30 feet thick. The graptolites indicate the zone 

 of JDidymoyraptus extensus (?) 1 50 



(2) Coarse grits 110 



(1) Coarse conglomerates, about GOO feet seen. 



