298 Scientific Proceedings, Royal Dublin Society. 
found while in the company of my colleague, Mr. MacHenry, at 
Puck’s Rocks, Howth, close to the spot where the late Dr. 
Kinahan discovered specimens of Oldhamia, and in the same slates 
that furnished me with certain spherical bodies, suggestively 
similar to Radiolaria. The new fossil presents itself as long, 
narrow, thread-like markings (fig. 1), which stand out in slight 
relief on the weathered cleavage faces of 
the rock, from which they are further 
distinguished by a difference in appear- 
ance due to difference in material, since 
the threads consist chiefly of quartz, with 
which is associated a small quantity of 
iron pyrites. The slate is of exceed- 
ingly fine texture, and greenish grey in 
colour: its cleavage planes are coinci- 
dent, or nearly coincident, with the 
original planes of lamination. The 
threads are confined to one particular 
band of slate not more than eight inches 
in thickness, and in this are only found 
through a narrow tract some two or three 
feet in width, where, however, they are 
very abundant, so that on breaking the. 
slate open, numbers will be seen on every 
fresh cleavage plane. mre. Gl 
The threads are of uniform breadth, Surface of a slab of slate bearing 
from 0°5 to 1:25 mm. across, and of 7 “#4 Henye Nat, size. 
indefinite length up to 5 or 6 cm.: for a centimetre or two they 
may preserve an almost straight course, but usually they run 
in a gently undulating fashion, making now and then a sudden 
turn, and sometimes apparently plunging abruptly inwards across 
the cleavage planes. Down the middle line of each thread, runs a 
longitudinal depression, bordered on each side by swollen margins, 
and the whole is crossed from side to side by numerous fine and 
close transverse ridges and furrows. 
Slices showing longitudinal sections may be readily prepared 
for microscopical examination by splitting off a thin lamina along 
the cleavage, and grinding it down to the requisite thinness: trans- 
verse sections must be cut in the usual way with a lapidary’s wheel. 
