274 '^^^^ Irish Naturalist* November, 



THE SILURIANS OF NORTH EAST IRELAND 

 AND THEIR CHARACTERISTIC FOSSILS. 



BY R. CI.ARK. 



Within the past four years revised maps on the one-inch scale have 

 been published by the Geological Survey of the country stretching 

 north from the Boyne to Belfast Lough, and westward into the 

 Counties Monaghan and Cavan. The greater portion of this area is of 

 Silurian age, and on the old editions of the Survey Maps issued many 

 years ago the beds were in general classed as " Lower Silurian." Subse- 

 quent investigations into the fauna of the Silurians, especially the 

 labours of Messrs. Lapworth and Swanston, increased very considerably 

 the knowledge hitherto existing, and rendered it desirable that a detailed 

 division of these beds should be undertaken. To obtain a key to the 

 various zones the abundant fauna of Coalpit Bay, Co. Down, was further 

 investigated with very satisfactory results, which materially aided the 

 revision in other localities, and allowed of its being carried out in detail. 



It was most interesting to note at widely distant localities the regularity 

 with which the sequence of the Coalpit Bay section was repeated, and the 

 Various bands from the Diplograptus palmeus of the LTpper Llandovery 

 to the cherty radiolarian seam of the Lower Caradoc again and again 

 met with. In the course of the author's researches fossils were procured 

 at numerous hitherto unknown localities, and in districts previously con- 

 sidered barren of palseontological evidence. This was especially so over 

 a large portion of Co. Armagh, from which a large collection of typical 

 JL/Ower Caradoc and Llandeilo Graptolites was made, and again in the 

 Clogher Head area of Co, Louth, where a fine series of Monograptus 

 similar to those at Portaferry, Co. Down, showed the beds to be of Upper 

 Llandovery age, and not Llandeilo as they had been supposed to be. 

 The occurrence of species new to this country is interesting, and the 

 discovery of Rastrites maximusy the absence of which had been com- 

 mented on by Professor Lapworth, was gratifying. A dichotomous plant, 

 Bet-wynia Carmthersi, was found at Coalpit Bay in Lower Llandovery. 



THE DRIFT MAP OF THE DUBLIN AREA. 



BY J. J. H. TEAI^I., K.R.S. 



The new map of the Drifts or surface deposits of the Dublin area 

 (sheet 112), is the outcome otthe combined work of the field staff of the 

 Geological Survey of Ireland during last year. A copy of the map was 

 exhibited, and it was pointed out that this constituted the first colour- 

 printed map produced by the Survey. The colour scheme adopted to 

 represent the 9 or 10 classes into which it was found possible to divide 

 the Drifts was briefly explained, and the relative ages of the different 

 divisions was pointed out. Some new and hitherto unexplained physical 



