208 C. Lapworth — Geology of Galashiels. 



the Old Eed Sandstone of BerwicksMre, in the north bank of Tweed, 

 about 200 yards above the railway viaduct at Leaderfoot, and are 

 charged with Diplograpsus pristis. 



The relation of this band of black shale to the associated strata in 

 this district is very obscure ; but, as we have never been able to 

 detect it either to the north or south of this line, it may be surmised 

 that there is no great dislocation of the strata, and no fold of sufficient 

 intensity to bring the band again to the surface. 



Every fossil yet found in these beds belongs to the fauna of Moffat, 

 and there is very little doubt that this line of black shale is the 

 continuation of that which is so persistent in that district; or, if 

 there be more than one band, this must be the higher, or that of 

 Dobbs' Linn and Frenchland Burn, which seems characterised by 

 the comparative rarity of Didymograpsus and other peculiar Llandeilo 

 forms. 



(B) The Gala Group. 



(1.) The Abbotsford Flags and GreywacTces. — These lie to the north 

 of the line of Anthracitic Shale that marks the approach to the 

 summit of the Moffat beds, from which I imagine they are separated 

 by some thick band of hard conglomeratic grit, which contains small 

 fragments of the Black Shales here and there in abundance. 



These peculiar grits seem to be pretty persistent, for I have met 

 with them in the neighbourhood of St. Mary's Loch, thirty miles dis- 

 tant along the strike, and apparently holding the same position with 

 reference to the Black Shales. "We have, however, never met with 

 these beds in situ in this district, though I have found angular 

 fragments of the peculiar stone strewn over the fields to the north 

 of Cauldshiels. These marked beds seem to point to a want of 

 conformity between the Gala and Moffat beds — locally, at least, if 

 not throughout the whole extent of the Lower Silurian of the south 

 of Scotland. 



Above this grit, as far as can yet be ascertained, come rapid alter- 

 nations of flaggy schists, with shaly partings, often bluish or dark 

 grey in colour, and containing here and there seams of slightly 

 carbonaceous shale, often tinged with oxide of iron ; sometimes finely 

 levigated and apparently unfossiliferous, sometimes of a more arena- 

 ceous character and containing fossils. 



These flaggy beds, of which there is no workable exposure in the 

 Gala country, have yielded in the Yarrow, above Selkirk, GraptoUthus 

 priodon (Bronn), G. SedgwicTcii (Port.), G. lobiferus (M'Coy), G. Nils- 

 soni (Barr), Bastrites triangulatus (Hark.), B. Linncei (Barr), and Dip. 

 teretiusculiis (His.). 



GraptoUthus priodon distinguishes the beds at once from those of 

 Moffat, and proves conclusively that we are now in a superior set of 

 strata. 



These flaggy and schistoze beds are succeeded on the north by 

 more solid-bedded greywackes, full of innumerable joints, and often 

 separated by beds of slightly arenaceous shale. The surfaces of the 

 joints are often coated with indigo-coloured matter, while the shales 



