Chap. XI.] 
OLD EED OF THE ' SILURIAN REOION.' 
247 
ral section. This unique fossil (Foss. 69) was first brought into notice by 
my accomplished friend the Rev. W. S. Symonds *, the specimen having 
been found by the Rev. W. Wenman. In the higher portion of this series, 
near Crickhowell, I formerly found the scale of a large Fish (Sil. Syst. 
p. 172), since ascertained to belong to Holoptychius. 
Lastly, a new species of the remarkable genus Pterichthys, Ag., so cha- 
racteristic of the Old Red of Scotland, has been discovered at Farlow, in 
Shropshire, in a yellow-coloured sandstone, which there occupies the 
highest portion of the formation, rising out from beneath the shale of the 
Carboniferous Limestone of the Titterstone Glee Hill, and graduating down 
into the mass of the red sandstone and subjacent cornstones. This species 
has been described by Sir Philip Egerton f ; and in the meantime it is well 
to remark that, whilst one form of the genus, which was first detected by 
Hugh Miller, lies in one of the lower beds of Cromarty, another spe- 
cies occurs plentifully at Dura Den in Fifeshire, where it is also in a 
yellow sandstone which has always been classed as the upper member of 
the group. 
When we follow this series of red beds from Shropshire and Hereford- 
shire through Brecknockshire and Carmarthenshire into Pembrokeshire, 
considerable lithological changes are seen to occur. Though the prevailing 
colour in the last-mentioned county is still red (the ' red rab ' of Pem- 
broke), some portions of the rocks consist of dull-green and brown flags 
or sandstones, and others of hard grey grits, which even resemble certain 
inferior Silurian deposits ; whilst true cornstone or limestone is rare, as are 
the traces of fossil Fishes. Yet the strata in question, to whatever extent 
attenuated in some tracts or placed unconformably on the Silurian rocks in 
others, occupy the same geological position as in the tracts of England and 
Wales previously mentioned, and lie clearly between the Silurian and Car- 
boniferous rocks %. In fact, few better sections of the Old Red Sandstone 
of Britain, in relation to the rocks beneath and above it, can be offered than 
are exposed around the magnificent landlocked bay of Milford Haven. 
(See Map.) 
We shall presently show the order of succession in rocks of the same age 
under a different and more slaty aspect on the south side of the Bristol 
Channel, in Devonshire, and indicate that, with a considerable change in 
their composition and a great increase in calcareous matter, the strata there 
contain many Mollusks and other marine animals unknown in the Silurian 
region, and equally distinct from Carboniferous species. 
Let us, however, previously consider the nature of the Old Red Sand- 
stone of Scotland, where, preserving much of the same mineral character 
* See Edin. New Phil. Journ., new ser., vol. vi. \ The yellowish sandstones which, in Pem- 
Oct. 1857. brokeshire, form the summit of this group may, 
t In a sequel to a paper by Professor Morris at least in part, be classed as the base of the Car- 
and the late Mr. G-. E. Boberts on the Carboni- boniferous rocks; that is, they are beds of trans- 
ferous Limestone and Yellow Sandstone of Oreton ition in which Lower Carboniferous fossils have 
and Farlow: Quart. Journ. G-eol. Soc. vol. xviii. been detected, 
p. 103. 
