[Proceedings Belfast Naturalists' Field Club— Appendix, 1879-80.] 



THE MOLLUSCA OF THE BOULDER CLAY OF THE 

 NORTH EAST OF IRELAND. 



By S. A. STEWART, 



Fellcnu of the Botanical Society of Edinburgh. 



Amongst the British deposits of the Glacial Period the Boulder Clay is 

 undoubtedly the most important. Though of small magnitude, as compared 

 with beds of greater antiquity, yet it exhibits such remarkable characters as 

 render it unique, and in the entire sedimentary series there are no rocks which 

 can be classed as altogether similar. Attempts have been made to prove a 

 succession of Glacial Epochs in not only Secondary, but also Palaeozoic times ; but 

 if Glacial conditions ever prevailed during those eras, only comparatively faint 

 and questionable evidences remain to us, and the epoch to which the Boulder 

 Clay belongs must still be regarded as the Glacial Epoch. 



The structure and physical characters of the Boulder Clay, as it occurs in 

 this district, are so distinct that it may be recognised without difficulty, and it 

 has been accurately described by successive writers from the time of Portlock 

 down to the present. It is a stiff, compact, unstratified clay, usually reddish 

 brown, but sometimes blue, very tenacious when moist, and containing numerous 

 boulders, as well as many smaller stones. These boulders and stones have 

 their angles more or less rounded off, their surfaces being in most cases 

 scratched or striated, and such as admit of polishing — especially the limestones 

 — are often beautifully polished. The larger portion of the stones have been 

 derived from local rocks ; but such as are not from the immediate vicinity have 

 been transported from somewhere to the north, sometimes east of north, and 

 often to the west of north. 



