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 



