‘ 
Prof. C. Lapworth—Ballantrae Rocks of South Scotland. 61 
Moffat Terrane in the Scottish Uplands we find the grand mass of 
more or less barren flagstones, shales, and greywackés which make up 
the overlying Gala or Queensberry Terrane. In the Girvan district 
the rocks belonging to this terrane form the local Dailly series: and 
are about 2500 feet in thickness, consisting mainly of repetitions of 
gray grits, flagstones, and red, green and purple shales. The 
Graptolitic fauna of the terrane is more or less transitional in 
character. Several forms are certainly peculiar to the Gala beds, 
but the older zones contain many survivors of the Moffat (Birkhill) 
fauna, while the higher zones yield several species which recur in 
the overlying Riccarton (Wenlock) rocks. The strata of the Gala 
Terrane grow somewhat thicker and coarser as they are followed 
eastward from Girvan over the Uplands, and fossils become rarer ; 
but even in the central parts of the plateau (Dumfriesshire and 
Selkirkshire) a lower (Queensberry) and a higher (Grieston) division 
ean still be roughly made out. Followed, however, still farther to 
the south-eastward, the rocks of the terrane soon imitate the example 
of the underlying Moffat series, becoming much finer in grain and 
decreasing in thickness. Finally, the whole terrane plunges in this 
direction (Hawick, etc.) below the Wenlock: rocks of Riccarton and 
Kirkeudbright, and when it re-emerges in the Lake district, it has 
dwindled down to an attenuated series of coloured shales and flags 
(Browgill or Pale Shales) with a collective thickness of less than 
300 feet.2 Hven here, however, its strata are still marked by the 
same two transitional subfaunas as those of the great Gala Group 
of the Scottish Uplands. : 
We find, therefore, that while the South Scottish strata of the 
Moffat Terrane are reduced to nearly a tenth of their original thick- 
ness within a comparatively short distance (25 to 50 miles) of the 
Girvan district, the thickness of the massive Gala Terrane remains 
practically undiminished over most of its visible range in the 
Scottish Uplands, and is even augmented in the central parts of the 
plateau. Hence in spite of its greatly inferior systematic importance, 
the Gala Terrane has a collective thickness over the Upland region 
far in excess of that of the underlying Moffat series. It follows, 
as a natural consequence of this fact, that when we regard the 
Upland region from the structural or tectonic point of view, we 
find the main mass of its visible rocky floor is formed of the rocks of 
this great greywacké or Gala terrane. ‘This has been crushed into 
innumerable wrinkles and puckers; the strata of the underlying 
Moffat series rising to the surface only along some of the larger 
anticlinal forms. As in other convoluted regions, the vast majority 
of these folds are of the class known as overfolds or inverted folds,— 
the axial plane of each fold being more or less inclined to the 
horizon; and thus the apparent dip of the truncated strata seen in 
section gives no clue whatever to the natural succession of the beds. 
But for many years it has been acknowledged on all hands that 
these overfolds are broadly related in position to two main struc- 
1 Q.J.G.S. 1882, p. 659. 
2 Marr and Nicholson, Q.J.G.S, 1888, pp. 674-678, etc. 
