^^^' 55'] BEDDED EOCKS OF COUNTY WATEKFOKD. 767 



ontological grounds^ with the Balcletchie Shales of Scotland, but our 

 knowledge of the fauna of the latter is very incomplete. It appears 

 meanwhile probable, in the light of my recent work, that the Tramore 

 Limestones mainly represent beds of a lower horizon than the 

 Balcletchie Shales. The latter contain Hartfell graptolites, but the 

 former are overlain by beds containing a general Glenkiln facies. 

 Thus we may have to regard the few Tramore Limestone species 

 in the Scotch area as merely the survivors of a migration from an 

 adjoining area. In a similar way the Cystideans and Cliasmopes 

 of the Upper and Middle Bala of the Lake District and Wales are 

 looked upon by Mr. Marr^ as the surviving representatives of an 

 earlier Scandinavian fauna which migrated from its old home. 



In the Waterf ord area, the difficulty arising from the fact that these 

 graptolitic Glenkiln shales were seen to overlie beds containing what 

 was held to be a Bala fauna probably led to the idea that the same 

 principles of classification of the beds as those employed in other parts 

 of Great Britain were not here applicable. Kinahan in one place ^ 

 says : — ' The groups of fossils indicative of the age of the English 

 Silurians are to some extent mixed up together in the Irish rocks, 

 on which account they are not in Ireland a reliable test of the age 

 of the rocks.' Elsewhere^ the same writer says: — ' In the rocks of 

 the Ballymoney Series the assemblage of fossils is to be compared 

 with that of the Bala rocks, but Caradoc fossils are not uncommon ; 

 while whenever black shales occur, no matter on what horizon, 

 they nearly alwaj'S contain fossils of Llandeilo type.' 



The graptolitic shales and associated beds forming the Carrig- 

 aghalia Series correspond palaeontologically with the Dicrano- 

 ^rop^its-shales of Wales, which, as described by Messrs. Marr & 

 Roberts ' and Mississ Crosfield & Skeat,'^ rest on the Llandeilo Lime- 

 stone. We might suppose that the underlying Tramore Limestones 

 would correspond closely with the latter, but such is not the case : 

 the faunas are completely different. The Didymograiytits-shales have 

 not been identified in the Waterford area, though on the opposite 

 side of St. George's Channel, in South Wales, they underlie the 

 Llandeilo Limestone. It may be urged that the ' Tramore Slates 

 may represent them, and this is possibly the case, but there is no 

 palaeontological evidence as yet in support of this view. 



In Sweden, below the Coenograptus gracilis-zone (which is at the 

 base of the equivalent of our Glenkiln Shales), comes the Ortlioceras- 

 limestone down to the top of the Ceratopyge-\idiik.'' Though the 

 term Or/7iocer«s-limestoue is used with somewhat different signifi- 

 cation and comprehensiveness by different authors and in different 



1 Geol Mag. 1897, p. 510. 



2 Quart. Journ. Geol. Soc. vol. xxxviii (1882) p. 325. 



3 Journ. Koy. Geol. Soc. Irel. vol. v (1878) p. 120. 

 * ' Geol. of Irel.' 1878, p. 25. 



« Quart. Journ. Geol. Soc. vol. xli (1885) p. 476. 

 6 Ibid. vol. Hi (1896) p. 523. 



■^ Tullberg, Sver. Geol. Undersokn. Ser. C, No. 50 (1882) ; G. L. EUes, Quart. 

 Journ. Geol. Soc. vol. liv (1898) p. 525. 



