JReports and Proceedings — Geological Socieii/ of London. 379 



The whole of the northern region is formed by a vast elevated 

 plateau of Upper or Visean Limestone, with a surface more than 

 100 square miles in extent, which rises on the north and east in 

 steep terraced cliffs, but to the south-west dips gently below the 

 so-called ' Coal-measure ' Series. The surface of this plateau is formed 

 of bare rock, devoid of vegetation and presenting the typical appearance 

 of a Karst landscape. The rainfall is considerable, but is nearly all 

 carried off by subterranean channels. 



The southern district presents a totally different aspect. The high 

 ground is no longer formed of limestone ; that on the east being 

 formed by Old E,ed Sandstone and Silurian rocks, that on the west 

 by Coal-measures. The older formations appear as two anticlinal 

 flexures, with a north-easterlj^ trend, forming the mountains of Slieve 

 Aught}" and Slieve Bernagh, between which lies a broad syucline of 

 Carboniferous Limestone. The margin of this syncline is formed by 

 Tournaisian shales and limestone, the successive zones of which can 

 be traced round its outcrop, while the Visean limestones occupy the 

 core. Much of the country is obscured by drift, chiefly derived from 

 the underlying rocks. 



A study of the limestone fauna shows that the Geological Survey 

 boundary between the Upper and Lower Limestones corresponds with 

 the transition from a Tournaisian to a Visean fauna ; the Lower Lime- 

 stone cannot, however, be separated from the underlying shales ; and 

 the Middle or ' Calp ' Limestone contains a fauna distinct from that of 

 the Upper or Burren Limestone, although they are not separable on 

 lithological grounds. An account is given of the zones recognized in 

 County Clare, and a correlation made with the sequence in other 

 British localities. 



The Old Red Sandstone is succeeded, to all appearance conformably, 

 by a thin series of sandy shales containing Brachiopods characteristic 

 of the Cleistopora zone, at the base of which a band is found containing 

 abundant Modioliform Lamellibranchs. The Zaphrentis zone is well 

 developed, the clathratus subzone forming the top of the Lower Lime- 

 stone shales, and the konincki subzone the lower stratified limestone. 



The most remarkable jjortion of the whole sequence is included in 

 the Syringothyris zone, which is represented by massive grey and 

 white mottled limestones, with a luxiariant molluscan fauna, large 

 Cephalopods being especially abundant. These beds show evidence of 

 deposition in shallow water, affording further proof of a mid-Avonian 

 period of upheaval. The fauna is compared with that of the Waul- 

 sortian phase of Belgium. The incoming of a Visean fauna is well 

 marked at the base of the Seminula zone ; in the middle of this zone 

 occurs an important bed of Oolitic Limestone, with abundant Gasteropods. 

 The Bibunophyllum zone attains a thickness equal to that seen in the 

 Midland area. Dj is chiefly characterized by the abundance of simple 

 Bihutwphylla, Cyathophyllum murchisoni, Clisiophyllid Lithostrotions, 

 and Frodudus hdissitno-giganteus ; Do by the occurrence of Lonsdalia 

 and Cyathophyllum regium ; and Dg by the abundance of Zaphrentids, 

 Caninia, and Densiphyllids, and the apparent absence of Clisiophyllids 

 and Lithostrotions. 



An account of the chief fossil localities, under the headings of 



