Cou7ity Dtiblm, Past and Present, 75 



Bail5^' The quarry west of St. Doolagh's, a hamlet 2^ miles 

 south of Malahide, where half of an ovoid hill has been already 

 cut awa}", offers perhaps the most fascinating field. As in all 

 compact limestones, the fossils stand out on weathered surfaces, 

 but are difficult to extricate entire. 



The Carboniferous sea was rich in corals of the old tetra- 

 corallan type; in brachiopods, particularl}^ Spwifer and /*;^- 

 ducttcs ; in gastropods, as Euoniphalus, which is coiled almost 

 in one plane ; and in cephalopods, as Nautilus and its extinct 

 straight all}^, Orthoceras. But the lower types still largely 

 predominated; taking as an example 345 species of shell- 

 bearing animals from the Lower Carboniferous Limestone 01 

 Ireland, as cited by Sir Richard Grifiith in one of his famous 

 lists, "" we find the following percentages: — Brachiopods 37.5, 

 Lamellibranchs 21.9, Gastropods 18' i. Utilising 527 species 

 living in modern British seas,^ the percentages are : — Brachio- 

 pods 1.3, Lamellibranchs 32.6, and shell-bearing Gastropods 

 no less than 48. Perhaps the life of the Carboniferous sea 

 seems still more remote from that of our times when we ex- 

 amine the larger forms. The fishes are all elasmobranchs 

 (sharks and ra3^s) ; or ganoids, like the now restricted Lepi- 

 dosteus of America and Polypterus of the Nile ; or dipnoi, like 

 Ceratodus of Queensland, a fish linked very closely to the 

 amphibians. Of the teleosteans, the familiar modern bony 

 fishes, there is not a trace in any country^ In Co. Dublin only 

 a few teeth and scales of fishes have been found. 



We know that amphibians walked upon the adjoining land 

 — in Upper Carboniferous times at any rate;-* but no true 

 reptile had arisen to assert itself among them. Plants have 

 become washed in here and there from the land,^ as, for 

 instance, near Loughshinny; but the great development of 

 low tj^pes of vegetation in the Carboniferous period must be 

 studied in beds which denudation has removed from Co. 

 Dublin. 



The Carboniferous Limestone has undergone two marked 

 types of alteration. Firstly, chert has frequently developed, 

 silica replacing the carbonate of lime, and flint}^ nodules and 

 bands resulting. These can be beautifully seen, running par- 

 allel to the bedding, in the low promontory north of the sands 

 at Rush. The chemical aspects of Irish cherts has been dis- 

 cussed by Mr. Hardman,*^ and secT:ions have been described by 



^ " Palseoiitolog}' of County Dublin," G. S. /., v., pp. 85-95. 

 -"Localities of the Irish Carboniferous Fossils," G. S. D., ix. (1S60), 



P- 37- 



3 " Report of the British Association for i860," p. 218. 



4 "Huxley and Wright, "On Fossil Vertebrata from the Jarrow Col- 

 liery, Trans. Roy. Irish Acad., xxiv. (1867), p. 351 ; Bail}', I\t'p. Bnt. Assoc.' 

 for 1878, p. 530, and for 1883, p. 496. 



5 Griffith, G. S. D., viii., 78. 



^ Sci. Trans. Roy. Dublin Soc, i. (new series), p 85. 



