296 Proceedings of the Royal Physical Society. 
to this view, an upward phase of undulation was established 
along a line nearly coincident with the structural axes of 
the present Southern Uplands of Scotland, the septum lying 
parallel to that, perhaps only a few miles to the north, and 
the main axis of depression farther north still. The effect 
of a gradual upheaval of that kind would eventually be to 
cut off, by slow degrees, the marine area in which the 
normal Upper Ludlow Rocks were in process of deposition, 
from the area to the north, which eventually passed into a 
lagoon. In this latter was deposited the material derived 
from the waste of the uprising area to the south, which 
went to form the red sandstones, whose remains are so well 
seen in Lanarkshire, and again in the heart of the Pentlands. 
In dealing with these several Old Reds, I have long found it 
convenient to distinguish this lowest member of the series 
from the others by some special name. As the rocks are 
best seen in Lanarkshire, where their true relations were 
first made out by Sir Archibald Geikie, I have ventured to 
term the whole of this lowest Old Red series the LANARKIAN 
Series. Probably most people will recognise the similarity 
of their stratigraphical relations to those of the Glengariff 
Grits, on the one hand, and to the Foreland Sandstones, or 
Lower Devonian Rocks, on the other; and as with these, some 
doubt may be entertained by many as to whether they should 
be classed as Ludlow or as a lower member of the Devonian 
series. What the full thickness of the Lanarkian Rocks 
was when complete we have no means of knowing; but I 
ventured to suggest during the Edinburgh Meeting of the 
British Association that the missing higher members of 
the series may at one time have included a band of marine 
limestone. Numerous blocks of such a limestone, contain- 
ing an assemblage of fossils remarkably like those of the 
Devonian Limestone of Plymouth, occur in the conglomerate 
which unconformably overlies the Silurian and Lanarkian 
Rocks. Its Brachiopoda were at one time identified as 
Devonian by Davidson, and many of its numerous corals 
are certainly, to say the least of it, closely allied to those 
of the Devonian Rocks. On the other hand, it is unlike 
any Silurian Limestone yet discovered in Scotland. 
