18 PROCEEDINGS OF SOCIETIES. 



that which we had just left, and containing the same fossils. This 

 widens out as it goes inland : we traced it for some distance to the back 

 of the village of Dunkineely. It is sometimes very hard to find this bed 

 on the beach, as in some winds it is nearly covered by the shingle, so 

 that it might easily be overlooked. At the point of Darney we found 

 a trap dyke cutting across the bedding in a direction nearly perpendi- 

 cular to the strike. It is very clearly marked, and is the only place 

 where we observed trap penetrating the sandstone, although we found 

 a good many dykes through the mica slate. About this locality Stigma- 

 riae occur in the greatest abundance. The fossil tree which Mr. Byron 

 discovered last year, and which is in the Museum of the Dublin Society, 

 was found near this dyke. We also found Sigillarise and some leaves 

 in the shaly beds which occur through the sandstones ; however, the 

 species is not perceptible in any of the specimens which we were able 

 to obtain. At Bruckless Tannery the sandstone changes into a red 

 conglomerate ; however, the character of the shales is not altered. The 

 lowest beds of this conglomerate are exceedingly coarse ; they may be 

 observed very well in the bed of the river at Hollybrook, and in the 

 cutting for a new road opposite Killaghtee Chapel. The mica slate ap- 

 pears underlying the sandstone a little beyond the bridge at Holly- 

 brook. ' 



At Green Island, in M'Swyne's Bay, we have greenish slates with 

 trap overlying them This island can be reached by land at very low 

 tides. At the back of Carntullagh, the headland which divides 

 M'Swyne's and Killybegs Bays, we found reddish slates and sandstones, 

 of a character different from those at Bruckless, and dipping at a higher 

 angle. These appear to be the beds which are converted into mica slate 

 in other parts. The centre of this headland of Carntullagh, and of 

 that of Drimanoo, at the other side of Killybegs Bay, is occupied by 

 trap, flanked on either side by mica slate. 



The constitution of the other district, which commences at Fin- 

 tragh, three miles west of Killybegs, is similar to that of the district 

 already described, but presents greater variety, in consequence of its 

 being intersected by faults, some of which are of importance. The 

 district is a complete basin, the beds dipping inwards all round. "We 

 commenced at Fintragh strand, where we found mica slate, and soon 

 came on the junction with the sandstone, the lowest beds of which 

 were not as coarse as in the other places where we observed the junc- 

 tion. The sandstone in this basin is not marked by such a profusion 

 of fossil plants as that under Dunkineely. In the overlying shale 

 in this place we observed plants in one or two places, very indis- 

 tinct. It is full of Turbinolia fungites and Encrinites, especially the 

 former. It seems to be a purer limestone than that at St. John's Point, 

 being harder, and of a bluish instead of a black colour. It has been 

 worn out into caves in several places. About a quarter of a mile beyond 

 the promontory of the Rinn we came on a fault in the limestone, and 

 further on, before we reached Shalwy, we found beds of black shale, 

 containing nodules, some of which appear to be impure ironstone. This 



