~ 
684. STRATIGRAPHICAL GEOLOGY. — [Boox VI. 
from near Shap to Duddon mouth. The following are the local sub- 
divisions with the conjectural equivalents in Siluria : 1 
Hay Fell and(Flaggy beds, with lamellibranchs abundant = (?)Tilestones. 
Kirkby Moor{ Massive greenish and grey sandstones, ea ee Lud- 
Flags . bands of fossils, Holopella abundant (ale 
(Calcareous beds, with madeline ski = age 
abundant : : { Limestone. 
Lower Lud- 
= low. 
its Hit Wen- 
Sandstone and shale, with eae 
Slates . 
Bannisdale 
fats blue flags and grits of great thick 
{ ness. 
Flags and ereywacke (Or thoceras subundu-) 
. ie latum, O. angulatum, Monograptus (Grapto- 
Coniston Grits . =f ower wees 
-) 
lock. 
lithus) Flemingii, M. colonus, Ceratiocaris 
Murchisoni), upwards of 4000 feet . 
: 1... {Dark grey coarse flags (Cardiola interrupta, 
Coniston Flags. { Orthoceras subundulatum), 1000 feet. 
Coniston Limestone (Lower Silurian) — {Caradoc or 
Bala. 
In the northern part of the Lake district a great anticlinal fold 
takes place. The Skiddaw slates arch over and are succeeded by the 
base of the volcanic series above described. But before more than a 
small portion of that series has appeared the whole Silurian area is over- 
lapped unconformably by the Carboniferous Limestone. It is necessary 
to cross the broad plains of Cumberland and the south of Dumfriesshire 
before Silurian rocks are again met with. In this intervening tract a 
synclinal fold must lie, for along the southern base of the uplands of the 
south of Scotland a belt of Upper Silurian rocks, dipping on the whole to 
the south-east, can be traced from the heart of the Cheviot Hills to the 
headlands of Wigtownshire. These rocks must reach a thickness of 
several thousand feet, but their top is nowhere seen. ‘They repose on 
some of the older parts of the Llandeilo series, with so close a coincidence 
of dip and strike that no decided unconformability has yet been traced 
between them. They consist essentially of shales, with a considerable 
proportion of greywacke bands towards the base. At different horizons 
they contain lenticular bands of a calcareous pebbly grit. But their most 
characteristic feature, and one which at once distinguishes them locally 
from the adjoining Lower Silurian rocks, is the occurrence of a brownish 
black, highly fissile shale, composed of layers in most cases as thin as 
ordinary writing paper and usually crowded with graptolites. . These 
peculiar bands occur throughout the whole series of rocks from bottom to 
top. They are sometimes so thin that 20 or 30 seams or ribs, each finely 
fissile, may be seen intercalated within the space of an inch of the 
ordinary shale or greywacke. Occasionally they form zones 80 to 100 
feet thick, consisting entirely of finely leaved graptolitic shales. As a 
whole these Scottish Upper Silurian strata resemble lithologically the 
corresponding series in Westmoreland, though here and there they 
assume the character of mudstones not unlike those of Shropshire. The 
abundant fossils in them are simple graptolites (Monog graptus (Grapto- 
lithus) Sedgwickii, M. Becki, M. Fleming, M. colonus, M. griestonensis, Re- 
tiolites geinitzianus, &c.). Orthoceratites come next in point of numbers 
1 The arrangement and thicknesses here given are those in the Kendal district as 
mapped by Mr. Aveline and Mr, Hughes in the course of the Geological Survey 
(Sheet 98, 8.E., Laplanation, pp. 6-13, 1872). 
