220
R. L. JACK AND R. ETHERIDGE, JT7N., ON PLANTS
ness, within a short distance. The following is a rough ad interim Table of the strata occurring in the trough cut by the section-line above referred to. It will be seen that the conglomerate beds of the series are thicker to the north-west of the axial line, while the finer deposits thicken out in the opposite direction.
Centre of Trough, Uamh Mhor $c.
Fine red conglomerate, with matrix of siliceous sand, enclosing pebbles of white quartz, porphyrite, and Silurian grit. The pebbles frequently angular 300 ft.
North-west side of Trough. Heads of Keltie and Euchil Waters.
ft.
B. Red pebbly sandstone, matrix
mainly siliceous 500
C. Greenish-grey flags and thin-
bedded sandstones 500
D. Conglomerate, stones up to 2
inches in diameter, mostly of white quartz, some of porphyrite, and various Si- lurian rocks 3300 ft.
Red Shales, conglo- merates, and grey sandstones 1100 „
Brown gritty sand- stones and brown shales with calca- reous nodules and crustacean -tracks (?)800 „
5200
F. Very coarse conglomerate
with well-rounded blocks, lap to 2 feet in diameter, of porphyrite and quartzite, chiefly porphyrite 1500
G. Bedded porphyrites abutting
against fault about a mile south of the section-line.
South-east side of Trough. Braes of Loune, Allan Valley and Sherijfmuir.
ft. B. Red pebbly sandstone 550
D
C. Greenish-grey flags and thin-bedded sandstones ...
Fine-grained brown sand- stones and dull brown shales 1700 ft.
Crumbling felspa- thic shales 500,,
Chocola te-coloured sandstones with calcareous nodules and a few pebbles . 8400 ,,
750
10,600
E. Bedded porphyrites of
Wharry Burn 200
F. Course trappean conglome-
rate 1100
G. Bedded porphyrites, mela- phyres and ashes of the Ochils, their base masked by a fault.
In the paper by Prof. Harkness, of 1862, above referred to, the " grey sandstone passing upwards into red sandstone," and overlying the trappean conglomerate (F in above Table), is stated to have yielded remains of Pteraspis. These Pteraspis-beda are probably inferior in position to those marked C in the above Section. Professor Harkness remarks, "no traces of plants, so far as I am aware, have been found in this [Bridge of Allan] neighbourhood ; nor are there any remains of Crustaceans."
It is in the flagstone group marked C that the plant-remains above described are found. No large quarry or natural section in the group fails to furnish at least a few traces of plants ; but here and there surfaces are to be met with which are quite black with
