Chap. VIII.] 
SILUKIAN EOCKS OF AYESHIEE. 
155 
So contorted and fractured are the strata of the southern part of the 
series, that it is indeed no easy matter to place them in their exact relative 
places — even after much labour bestowed on the coast-sections of his native 
county (Wigton) by my friend Mr. John Carrick Moore. The black glossy 
slates of Cairn Eyan, and certain red schists, might lead us, from analogy, 
and from their containing the same species of Graptolites, to suppose that 
they represented the older portion of the previous sections, which lie above 
the Longmynd or bottom rocks. On the other hand, they are associated with 
a coarse conglomerate containing pebbles of granite and porphyry, with here 
and there blocks two feet in diameter ; and this conglomerate so much re- 
sembles a rock of the Ayrshire district about to be described, which clearly 
dips under certain fossiliferous schists (of Kennedy's Pass), that the pebble- 
beds of Wigton and Ayr may be eventually placed on the same parallel. 
Along the coast, however, from Correrie Burn to the Stincher Eiver, they 
are separated by so much igneous rock that it becomes impossible, without 
long and continuous labour, to coordinate the disrupted masses. 
With the northern portion of this section I am best acquainted, and to 
it I now call attention. From the mouth of the Stincher to Kennedy's Pass, 
south of Girvan, the eruptions of porphyry, greenstone, and syenite are 
indeed on a grand scale (Knockdolian, Bennan Head, &c). Owing to these 
great extrusions from beneath, the Silurian strata, accompanied by much 
serpentine and many metamorphosed schists*, have there been thrown into 
at least three flexures within the distance of a few miles, on each of the 
axes of which, or on the Stincher, Assell, and Girvan Rivers, limestones of 
the Lower Silurian age are brought to the surface. These schists and 
limestones are overlain in the contiguous troughs by other rocks, one por- 
tion of which consisting of coarse conglomerates; and another of shelly 
sandstone, represent parts of the Caradoc rocks ; whilst certain sandy 
and calcareous flagstones seem, by their fossils, to be equivalents of the 
Llandovery rocks, and to indicate a passage into the lower member of the 
Upper Silurian. 
Eeferring for details to the memoir above cited, I will here very briefly 
describe some of the salient features of these Ayrshire deposits. The lime- 
stones on the Stincher and the Girvan Eivers contain the following fossils : 
— Orthis calligramma, 0. confinis, Leptsena sericea, L. quinquecostata, 
Cheirurus gelasinosus, species of Illaenus and Asaphus, Pleurorhynchus 
dipterus, and Corals of the genera Heliolites, Favosites, Omphyma, Stre- 
phodes, &c. 
Most of the above species are Caradoc types ; and with them is also found a 
species of the genus Maclurea of Hall, which is characteristic of the Chazy 
Limestone, one of the marked Lower Silurian deposits of North America. 
* The igneous and metamorphic rocks of this gards as metamorphic I still consider to be of 
tract have recently been described in considerable igneous and eruptive origin, not only from their 
detail by Mr. James Geikie, of the Geological composition and structure, but from the part they 
Survey, in the Quart. Journ. G-eol. Soc. vol. xxii. play in disturbing the sedimentary strata, 
p. 513. Some of the rocks which Mr. Geikie re- 
