The Geologist at the Ltmcheon-table. 43 



ossicles. Veins of calcite traverse the mass, as in the well- 

 known Devonian marbles of Plymouth, and more delicate 

 thread-like veins, filled with a deep red material, run in the 

 direction of the general movement of the breccia. 



The other three tables illustrate the fossiliferous Carboni- 

 ferous marbles of this country. One is a little known and 

 beautiful variety of " grey fossil" limestone, consisting almost 

 entirely of fragments of crinoid stems. One or two small 

 pieces of coral alone break the uniformit}- of the great area of 

 encrinites ; these sea-lilies must have here grown as a veritable 

 forest. Iron oxides have delicatel}^ infilled the hollows of 

 the stems, and have even stained with tender browns and 

 pinks the whole substance of some of the ossicles. This 

 remarkable stone has been quarried in the neighbourhood of 

 Lough Erne. 



Another slab comes from the famous quarries of black 

 marble near Galway city. It has been chosen on account of 

 its strong contrasts of effect, the fossils being grouped in it 

 with a certain daring picturesqueness. From one angle, a 

 great branching mass of the tubular coral called Syri7igopora 

 spreads across the stone for a distance of some 25 cm. At the 

 opposite angle is a vertical section of a valve of the brachiopod 

 Prodtictus, while in between is a section showing the two 

 valves as circles lying one within the other. The smaller 

 valve, being concave, is thus often traversed by sections which 

 also cut across the larger and convex valve. 



Nearer to the Syringopora in this table is a bold section of 

 Pj'od7cctus, 10 cm. across, which largely influenced the selection 

 of this particular slab. A fine simple coral can be seen 

 growing from its exterior ; and here we at once have a picture 

 of the floor of the Carboniferous sea in Co. Galwaj^ with large 

 valves of dead brachiopods scattered upon it, their concave 

 sides characteristically facing downwards, like those of 

 lamellibranch shells on our own shores. Their upper surfaces 

 furnished the abundant simple corals with a fairly stable basis 

 of attachment, while the ramifying and more massive reef- 

 building forms held together and even wrapped round and 

 included other forms. Thus the example of Syringopora in 

 this table shows one or two other corals, Zaphrentis in all 

 probability^ entangled in its spreading meshes. 



