[Proceedings Belfast Naturalists' Field Club — Appendix , 1879-80.] 
THE MOLLDSCA OF THE BOULDER CLAY OF THE 
HORTH EAST OF I RELA ND. 
By S. A. STEWART, 
Fellow 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. 
