302 C. LAP WORTH ON THE MOMAT SERIES* 



The name of the division is derived from the burn of Glenkiln, 

 near Dumfries, where its fossiliferous bands are most fully exhibited, 

 and where they yield their fossils in the greatest variety and abun- 

 dance. The succession is, however, there greatly interrupted by 

 numerous faults which, running along the strike of the beds in a 

 mass of very similar deposits, are almost impossible to detect. We 

 are, unfortunately, unable to indicate any locality in the Moffat 

 district where there is an absolutely uninterrupted sequence. The 

 evidence for the order here given is partly physical, partly palseon- 

 tological; it is consequently open to such slight corrections and 

 additions as may be found to be necessary when the corresponding 

 deposits in the Lammermuirs, Lead Hills, and Galloway are fully 

 described. 



At Hartfell (fig. 27, p. 309) the summit-bed of the Glenkiln Shales 

 is seen to be formed of 4 feet of hard flaggy rock. This reposes 

 upon a seam of dark shivery mudstone 8 feet in thickness, which 

 passes in its turn into a group of pale yellow or orange- coloured 

 shattery mudstones of indeterminable thickness. 



At Craigmichan (fig* 3, p. 263) the same flaggy band is recognized 

 in a corresponding position, supporting the main mass of the Hartfell 

 Shales, and surmounting similar dark-gray and orange-coloured 

 mudstones. Although only one or two insignificant faults are actually 

 to be detected in the cliff below, yet no two sections, measured from 

 the grey band into the heart of the Glenkiln Shales, are precisely alike. 

 In each section we recognize a thickness of from 40 to 60 feet of 

 barren shales of a peculiar character, apparently interposed between 

 the highest visible black-shale bed of the Glenkiln group and the 

 lowest black-shale band at the base of the succeeding Hartfell divi- 

 sion (fig. 3). The evidence derived from other exposures of 

 these strata, however, renders it almost certain that they consti- 

 tute in reality the lowest visible subdivision of the Glenkiln Shales, 

 being actually inferior in geological position to the apparently under- 

 lying black beds, which are cut out above by the faults seen near 

 the base of the Hartfell Shales. 



The majority of the beds composing the lower Glenkiln subdivision 

 are thin-bedded shales, often finely laminated. A few show a ten- 

 dency to run into concretionary forms, and occasionally weather down 

 into irregular ellipsoids, exteriorly of a yellow or rusty orange-colour. 

 Some are shattery mudstones, breaking up into small prismoidal 

 splinters. Others, again, are coarser in their texture, and have a 

 rough harsh surface ; and where greatly hardened split up into thick 

 plates with a rugged uneven face, as in many bedded traps and 

 ashes, to which, indeed, in other respects several of these beds bear 

 no inconsiderable resemblance. All these strata, as might, indeed, 

 have been inferred from their mineralogical character, are totally 

 barren of true fossils ; but many are pierced in all directions by 

 worm-burrows and the like. 



The most striking feature of these barren beds is the presence 

 among them of seams of hard flagstone, varying in thickness from a 

 few inches to more than a foot, and occurring in definite layers 





