NOTES AND QUERIES. 



385 



New Fossil Locality op Mollusca in the Scottish Old Red. — The 

 new deposit of fossil organic remains in the Old Red Sandstone at Dron, as 

 noticed by me in the last " Geologist," becomes, upon further examination, 

 of the greatest interest as well as theoretic importance in a scientific point of 

 view. I shall, therefore, in a few details give the substance of the discovery, 

 showing the general bearings, relations, and character of the rocks in the dis- 

 trict, and furnishing materials, whether of controversy or agreement, for future 

 investigation among geologists. 



The district in question occupies a central position in Strathearn, skirting 

 the Ochils on the south, and trending northerly towards the hill of Moncreiffe, 

 which forms an outlier of the Sidlaws. The intermediate space of nearly three 

 miles in breadth, is filled with deep alluvial clays, peat, and gravels, and forms 

 an extension of the Carse of Gowrie deposits intersected by the river Tay. 

 An elevated ridge occurs at Dron, near the church, which rises steeply towards 

 the west • it is about a mile in length, terminating in the red sandstone quarries 

 of Pitkeathly, and separated by a deep hollow from the Ochil range of trap- 

 porphyry. The outcrop of the new fossil beds is on the slope to the south of 

 this hollow, forming an insulated little basin of blue marly clays, interlaminated 

 with hard micaceous flagstones, and showing all round indications of great 

 denudation. 



Extending the view eastward, the basin-estuary of the Tay opens up widely, 

 enclosing the various members of the Old Red Sandstone series — the con- 

 glomerate of Glenferg, the yellow-spotted beds of Abernethy, the cornstone of 

 Clunie and Newbigh, the tilestones of Parkhill, and all of which have their 

 correspondents at Clashbennie, Meurie, Inchture, Balruddery, Tearing, Carmy- 

 lie, and Forfar. The intermediate space westerly, from the Ochils to the Gram- 

 pians, averaging fifteen to twenty miles in breadth, is occupied with the lower 

 Devonian series, embracing all the rich fossiliferous rocks of Forfarshire, the 

 deep-red beds towards Birnam, Crief, Donne, and Dumblane ; and which, in 

 some of the members near Gleneagles and Dalmyatt, contain specimens of 

 Parka deeipiens, Pteraspis, and Cephalaspis. The outgoing of the whole, east 

 and west, from the terminating shores of Arbroath and Montrose, being the 

 environs of Lochlomond and Dumbarton. 



The relation of every one of the above series of rocks, forming one geo- 

 logical group, may be traced in the vicinity of Dron in juxta position each to 

 each in an easy forenoon walk. The depth of the deposit, as exposed at the 

 mill-dam, varies from twenty to thirty feet. The newly-discovered fossil-bed 

 — so attractive yet to be to science — forms the centre-point which underlies 

 the whole. It stretches along the narrow ravine to the foot of the Ochils, 

 where it becomes enclosed among the trap-porphyries, and where a fine water- 

 fall (the Ramheugh) plunges over its indurated edges. The " cornstone" of 

 the series is not now observable, being covered up by the improvements of 

 modern husbandry ; but it has been long known as existing, in situ, in the 

 neighbouring fields. A few hundred yards distant the quarries of Pitkeathly 

 — the Holoptychian red — shows the position of these beds. And, last of all, 

 an insulated section of what I regard as the Dura Den yellow sandstone, and 

 ferruginous marls, crowns all the underlying strata; it is exposed to the depth 

 of thirty to forty feet in the woods of Wester-Dron farm, and the nearest con- 

 tinuation of which is ten miles off, at Glenvale, on the Lomonds. When 

 fossils were not sought after, or formed no attraction to the curious, these 

 upper rocks have been extensively worked, and all their ganoid treasures, if 

 ever exhumed, lost to science. 



The organic remains just discovered in the lower grey sandstone of the series 

 consist of shells and microscopic Crustacea, and are, so far as I am aware, the 

 first specimens of conchifera yet detected in any of our Scottish Devonian 

 YOL. iv. 2 S 



