214 E. T. Hardman — Fomliferoas Beds of Lough Neagh. 



VII. — The Fossiliferous Clay Beds oveklying Basalt, Lough 

 Neagh, and the Geological Age of that Lake. 



By Edward T. Hardman, F.C.S., etc. 



TBEGBET that I have not had an earlier opportunity of replying 

 to a paper in the -Geological Magazine tor February, p. 62, by 

 Mr. William Swanston, F.G.S., on the above subject. I shall now try 

 to compress my remarks into the smallest possible space. 



1. With regard to the Fossiliferous Clays in theCrumlin Biver : — 

 Mr. Swanston is mistaken in supposing that the discovery of shells 

 in these beds " proved to the satisfaction of the author (myself) and 

 Professor Hull, F.B.S., . . . that the beds were undoubtedly of 

 Pliocene age." Here Mr. Swanston has reversed matters. On the 

 contrary, this conclusion had been arrived at two years before, and 

 at the Belfast Meeting of the British Association I stated my con- 

 viction, chiefly from stratigraphical evidence, that the Lough Neagh 

 Clays were of Pliocene age, and the similarity of the beds led us to 

 the conclusion that the shells might be of Pliocene age. 



2. I never led it to be believed that I was " convinced " that the 

 shells in question " belonged to a species of Unio." And even before 

 suggesting that " they appear to belong," etc., I had consulted Mr. 

 W. H. Baily, F.G.S., whose authority as a Palaeontologist I need not 

 here enlarge upon. Moreover, not being convinced by the examina- 

 tion of a few mutilated specimens, I even pointed out the necessity 

 for a thorough examination of the specimens on the spot, to which 

 hint doubtless Mr. Swanston is indebted for his collection. 



3. I am at a loss to know if the opinion of Dr. Gwyn Jeffreys, 

 F.B.S., is positive or conjectural. Such a phrase as "I can come to 

 no other conclusion " is somewhat ambiguous. There could be but 

 little difficulty in determining absolutely the common mussel as it 

 occurs in drift. 



4. Here it occurs to me: Can Mr. Swanston and I be referring 

 to exactly the same locality ? In the section I described there occurs 

 positively no Boulder-clay whatever ; though there is abundance of 

 it both higher up and lower down the river, from which Mr. 

 Swanston may have obtained his shells. But the clays resembled 

 in every respect many of the beds of undoubted lacustrine clay of 

 Lough Neagh, and were perfectly similar to those found not far 

 distant on the Glenavy Biver; and also to many of the beds used 

 for pottery manufacture to the south of the lake. Furthermore, the 

 shells I noticed are extremely thin and fragile, hardly thicker than 

 a piece of notepaper. They appear in every way suited for the 

 quiet waters of a lake, but seem ill-fitted to resist the stormy 

 buffetings of a sea-shore. The clays in which they occur are deposits 

 clearly formed on the ancient margin of the lake, as denoted by old 

 shore-cliffs of basalt close by. Even granting that the shells be 

 Mytilus, it would not be outside the bounds of possibility that the 

 lake might formerly have communicated with the sea, as it is now 

 only 48 feet higher ; thus the shells might be true lacustrine fossils 

 deposited before the Glacial period. 



