146 
SILTJKIA. 
[Chap. VIII. 
Homalonotus bisulcatus, Calymene duplicata?, and Phacops apiculatus. 
These are all true Lower Silurian types of the Caradoc formation. 
In the north-western and mountainous part of England, the Silurian 
rocks appear in great force in the counties of Westmoreland and Cumber- 
land and the adjacent tracts of Lancashire and Yorkshire. Though some 
of the members there assume a lithological aspect different from what 
they maintain in the Silurian and "Welsh region, they have been clearly 
paralleled by several geologists with those original types. Professor Sedg- j 
wick, who has most studied the Lake region (which I have also traversed 
on five occasions for purposes of general comparison), and who has described I 
it in a series of valuable memoirs, has grouped the lowest fossiliferous 
limestones, or those of Coniston, with his Cambrian rocks, though during 
several years he identified them by means of the published fossils with the 
Lower Silurian and even with its upper portion. 
In truth, the region of Siluria, as geologists now admit, afforded the key ' 
by which the fossiliferous strata in the north-western tracts of England 
were brought into order and had their proper places assigned to them. 
In Cumberland, however, where the lowest members of this series rise up 
into the lofty mountains of Skiddaw and Saddleback, parts of these masses 
of schists, though simply of Lower Silurian age, are in the condition of fine, 
glossy, chiastolite slates. 
The lowest of these rocks had afforded no fossils except Graptolites and 
Fucoids, and were considered by Professor Sedgwick to be of as high an 
antiquity as the lowest Cambrian beds of North Wales. The researches, 
however, of Professor Harkness and Mr. Nicholson have ascertained that 
this is not the case. They have shown that these Skiddaw slates of Cum- 
berland are not even so old as the Lingula-flags of North Wales, but are 
of Lower Llandeilo age, as proved not only by containing the very same 
species of Graptolites which occur in that subformation, but also Trilobites, 
Orthidae, and other fossils which characterize that zone. In vain, there- 
fore, in such a country has the geologist sought for the equivalents of the 
bottom rocks, described in the earlier chapters as overlain conformably by 
strata with Lingulse and Trilobites. Nowhere in the Lake region have the 
repeated labours of geologists or fossil-collectors detected the ' primordial 
zone ' of Barrande — or Lingula-flags. 
The Skiddaw (or Lower Llandeilo) slates are overlain by vast masses 
of green slates and porphyries, in which scarcely the trace of a fossil has 
been found, owing doubtless, in great measure, to a superabundance of 
igneous matter, which has been still more copiously given out in this Lake 
region than in the mass of the Llandeilo rocks of the typical region (see 
above, p. 79). To the south of these lofty and picturesque mountains, 
we come to the Coniston limestone, with its overlying flagstones. At that 
zone only do we begin to find a rich fauna ; and, judging from the organic 
