TIIK CARBONIFEROUS SYSTK.M 



273 



it is only in the outer part*, where the beds rise into hills, that 

 tin- complete succession can be studied ; the best sections are found 

 on it* western, eastern, and southern borders. 



As the series above described is traced southward through Mayo 

 and Roscommon into Galway it exhibits a change similar to that 

 which takes place in England, namely a thinning of the sandstones 

 and shales and a thickening of the limestones, till the series passes 

 into a great limestone formation nearly 3000 feet thick, with the 

 same black shales above and a still thicker set of basal sandstones. 

 The following is the lithological succession in Galway and Clare 

 according to Mr. Kinahan and the Survey : 



Upper limestone shales 



'Limestone with layers of chert 



Upper limestone 



Lower limestone- 



Black limestone and chert) 

 t Upper cherty zone / 



'The Fenestella limestone 



Lower cherty zone 



Shaly limestone . 



Lower limestone shale . 



tot 



. 80 

 . 1500 



. 400 



. 300 



. 100 



. 400 



. 150 



About 3000 



The zonal distribution of fossils in the limestone of Clare county 

 has recently been ascertained by Mr. J. A. Douglas, 13 and proves to 

 be comparable with that in the Bristol sequence. He tabulates 

 the beds and zones as follows : 





