ipi.v Yi\^c.\i,— Shelly Drift of Co. Mayo. 3 
distance of twenty-two miles as the crow flies, was examined 
during a total of thirteen days, and the Hmits of the shelly 
drift ascertained. From Lackan Bay around Downpatrick 
Head to Ballycastle is pleasant open country, but from 
Ballycastle westward the land gets steadily wilder and 
bleaker, until between Belderrig and Porturhn it becomes 
desolate in the extreme. It was found that the limits of the 
Shelly Drift were roughly the eastern slope of Glenulra, and 
the western slope of the Belderrig River valley; and on the 
ground between these two points most of the time was spent, 
with the result that as regards the mollusca a number 
of new records may be added to Canon Grainger's list — 
and that the Boulder-clay near Belderrig, containing Tellina 
cakarea, is found to be of later date than the till in Glenulra 
and of the overlying brown Boulder-clay. The following 
appears to be the sequence of the Glacial deposits in this 
district : — 
5. Sands and gravels. 
4. Belderrig Boulder-clay with Tellina calcarca. 
3. Brown Boulder-clay, mostly of local origin. 
2. Stiff blue Boulder-clay (Till). 
I. Boulder-bed in the Owenbeh5^ 
1. The Boulder-bed in the Owenbehy is composed of 
rounded and sub -angular boulders of sandstone, with 
practically no clay and with no shells. It has a thickness 
of about two feet, and occurs in the left bank of the river, 
which it occupies for about 100 yards. As ^this bed does 
not appear in any other section in the district it may be 
the old river debris of pre-glacial times. 
2. The Till or stiff blue clay with erratics and shell- 
fragments occurs in three places in the district — Glenulra, 
at an elevation of about 160 feet, and the eastern and 
western branches of the Owenbehy, at about 270 feet. 
In each case it makes its appearance in the same manner, first 
becoming visible in the bed of the stream between the river 
boulders ; then it gradually begins to appear from 
under the local Boulder-clay in the river -bank, and having 
attained a thickness in most cases of about 4 feet it dis- 
appears again under the local Boulder-clay, after running 
for about 100 yards. The erratics noted in the till were 
striated limestone, sandstone, mica-schist, grits and granite. 
a2 
