TRANSACTIONS OF SECTION C. 387 



MONDAY, SEPTEMBER 4. 



Joint Discussion with Sections E and K on the Relation of the present 

 Plant Population of the British Isles to the Glacial Period. — 

 See p. 573. 



The following Papers were then read : — 



1. On the Lower Carboniferous Strata of the Bwndoran District 

 in South Donegal. By W. B. Wright. 



[Published by permission of the Director of the Geological Society of Ireland.] 



In the month of March in the present year an attempt was made by the 

 writer on behalf of the Geological Survey to get some evidence of the palaeonto- 

 logical horizon of the Lower Carboniferous strata of the North-West of Ireland. 

 The district about Bundoran, on the borders of Donegal, Leitrim, and Sligo, 

 was selected as representative and well exposed. Fossils were collected on the 

 various horizons and sent to Messrs. G. W. Lee, R. G. Carruthers, and Ivor 

 Thomas, of the Geological Survey of Great Britain, who kindly undertook to 

 deal with the material obtained. It will of course be understood that to then 

 expert knowledge the result is for the most part due. 



The lithological subdivisions of the Lower Carboniferous strata in the Bun- 

 doran district are summarised in the following table : — 



Feet 

 Millstone Grit (so-called) 



Yoredale Shales (so-called) 



Yoredale Sandstones (so-called) 



Upper Limestone 



Upper Calp Shale 



Calp Sandstone 



Lower Calp Shale . 



Lower Limestone 



at least 500 

 300 to 400 

 about 500 



1,100 

 500 to 800 

 300 to 500 



500 to 1,000 



The Lower Limestone has a conglomeratic base resting on the gneiss ; the 

 Lower Limestone shale, so constantly present at the base of the limestone in 

 other parts of Ireland where the Carboniferous strata pass down conformably 

 into the Old Red Sandstone, is completely absent. 



The species of brachiopods obtained from the various fossiliferous horizons 

 of this series all indicate, according to Messrs. Lee and Thomas, Lower and 

 Middle Visean horizons (say C and S of Vaughan's classification). There is no 

 indication of any Tournaisian beds whatever. Neither is there any indication 

 at the top of the series of Upper Visean beds (D zone). The beds which have 

 hitherto been known as ' Yoredale Shales ' yield the characteristic Pendleside 

 fossil Posidonomya becheri, but this is associated with a cephalopod fauna 

 which is not that of the Pendleside Series of England but of the main mass of 

 limestone beneath the Pendlesides of Hind. 



The corals, although found in great numbei's, yielded less definite results, 

 but, so far as they go, they indicate in the opinion of Mr. Carruthers an 

 abnormal phase of the Lower and Middle Visean, peculiarly rich in zaphrented 

 and other small corals. There is a complete absence of the typical Tournaisian 

 forms Zaphrentis delanouei and Z. konincki, and no specimens were observed 

 of such characteristic 'D' corals as Lithosfrotion junceum, the Lonsdaleoids 

 or the Dibunophylla. 



The conclusion drawn from a study of the fauua, that the Carboniferous 

 strata of Bundoran are throughout of Visean age, leads to an interesting 

 stratigraphical result, for it establishes palseontologically for this area the trans- 

 gression invoked by Jukes on purely lithological grounds to account for the 



c c 2 



