DESCRIPTION OF THE FORMATIONS 369 



interbedded lavas, these rocks form the whole axis of the Sidlaws, all along 

 which they are quarried for building and paving material. The well-known 

 Carmyllie quarries are in the middle of this series. Passing upward, the 



"Caimconnan Series is reached, distinguished by its coarser materials, prin- 

 cipally dull red or grey grit with bands of conglomerate. The conglomerates 

 are more particularly developed on the north side of the anticline, as at Turin 

 Hill, north of Rescobie Loch. This series should appear on the coast in Lunan 

 Bay, but it is entirely hidden by the sand and alluvium. At the south end of 

 the bay another series of lavas, admirably exposed for study, intervenes be- 

 tween it and the 



"Red Head Series, which forms the bold cliffs from the promontory of that 

 name southward to Rumness. In its lower part it consists of fine red thin- 

 bedded sandstone with bands of hard bright red shale, while the upper por- 

 tion is made up of thicker-bedded sandstone. Some six or seven miles to the 

 southwest, at Arbirlot, the lower part of this series, as seen in the banks of 

 the Elliott Burn, consists mainly of blue and grey shales, with partings of 

 sandstone, having so strong a resemblance to some of the rocks of Carmyllie 

 as to have led Hugh Miller to consider them as a repetition of that series. 

 This case illustrates very well the rapid lateral variation to which all the beds 

 of the Old Red Sandstone are liable. 



"The Auchmithie Conglomerate overlies the previous group in the cliffs just 

 north of the village so named. The series consists of three main masses of 

 conglomerate, with intervening sandstones and conglomerates. The pebbles in 

 the conglomerates are well rounded, fairly large (generally 1 to 6 inches, 

 rarely 12 inches), and, as usual, are mostly quartzite. The thickness of this 

 conglomerate series diminishes along its outcrop to the southwest. 



"The Arbroath Sandstone is the highest series of the Lower Old Red seen 

 on the Forfarshire coast. Coarse, gritty, sometimes pebbly sandstone is its 

 component rock, always red in color. Just above the base of the series, by the 

 Signal Tower at Arbroath Harbor, there is a single band of grey grit and 

 marlstone on the shore, containing nodules of limestone from the size of a pea 

 to 1 foot in diameter. This is noteworthy in view of the almost complete ab- 

 sence of lime from the Lower Old Red System. . . . 



"The EdzeU Shales . . . overlie the Arbroath sandstones. They are gen- 

 erally bright red fine sandstones, shales, and marls, either hard or soft, fre- 

 quently mottled with small circular patches of pale yellow, grey, or green, or 

 more rarely with bands of the same color. . . . 



"The volcanic rocks of the district do not call for description here. It may 

 suffice to remark that they are, with very rare exceptions, in the form of con- 

 temporaneous interbedded sheets, and are merely a continuation of the series 

 of the Ochil Hills, where they have been described in detail by Geikie and 

 others (A. Geikie, 1900). 



"Attention must now be drawn to a point, the importance of which has not, 

 I believe, been hitherto recognized. All the recorded fossils from this dis- 

 trict — and I suspect that the same applies to Perthshire — are from a very 

 limited series of horizons near the middle of the Lower Old Red System, the 

 Upper Old Red being, of course, left out of account. The Carmyllie series is 

 the fossiliferous group par excellence, while a few of the worked localities 

 may lie in the Cairnconnan series (e. g., Tilliewhamland quarry, Turin Hill), 



