Chap. XI.] 
FOSSILS OF THE OLD EED SANDSTONE. 
265 
Fochabers, and largely in Tynet Burn, and at Gamrie, on the coast of 
Aberdeenshire. 
In tracing the Old Eed group upwards on the eastern flank of the 
Grampians, from the flags or paving-stones of Arbroath, with their Pte- 
rygoti and egg-like bodies, through the Cephalaspis-beds, to the deep- 
red overlying sandstones of Perthshire (no bituminous schists being there 
known), we begin to find Holoptychius, a genus which has been con- 
tinued into the Lower Carboniferous rocks. The species, however, which 
occur in the deep-red sandstones of Perthshire, and particularly the 
splendid specimen from Clashbinnie, H. nobilissimus (PI. XXX VII. f. 9), 
are entirely distinct from those forms which occur in the highest strata, 
that are observed to pass up into the Carboniferous rocks. 
It is only in certain reddish and yellowish sandstones and shales, as seen 
in Fifeshire and the Lothians, that the geologist can be said to enter among 
those strata which here and there are linked on to the Carboniferous 
rocks above, as they unquestionably are to the Old Eed Sandstone below, 
and which, according to the predominance of their fossil contents, may be 
grouped with either deposit. Like the strata which connect the Upper Si- 
lurian with the Old Eed group, these yellow sands and shales are the true 
transition -beds which unite the Old Eed with the Carboniferous series. 
They are the beds in which the late Dr. John Fleming long ago pointed 
out the occurrence of Shells and Plants indicative of terrestrial and fresh- 
water conditions *. 
Other species of Holoptychius occur both in the red- coloured and yellow 
sandstones on either coast of the South of Scotland ; and, again, some spe- 
cies of this genus, distinct, however, from all those of the Old Eed, are 
found in the lowest Carboniferous strata. 
It is worthy of being again noted, that the only scale of a large species 
of Holoptychius which I met with in preparing the description of the Si- 
lurian region was in one of the upper beds of the Old Eed of Hereford- 
shire, near Crickhowell, where that formation passes conformably under 
the Carboniferous Limestone of the South- Welsh coal-field f . 
These upper beds are marked at Dura Den in Fife, and at Farlow % in 
Shropshire, by the presence of Pterichthys, accompanied in the Scotch 
locality by Holoptychius §. The species, however, are distinct in both cases 
from those of the older or middle beds in Caithness and the Orkneys, as 
well as from those of the overlying Carboniferous rocks. Among these 
* See Edinburgh Journal of Natural Science, many well-preserved Ichthyolites in this yellow 
vol. iii. sandstone of Dura Den. He informed me that 
t See Sil. Syst. p. 171. the yellow sandstones of Dura Den contain 
J See the paper on the yellow sandstones at Ichthyolites of the genera Platygnathus, Dip- 
Farlow by Messrs. Morris and Eoberts, Quart, lopterus, Glyptopomus, Holoptychius, Pterich- 
Journ. G-eol. Soc. vol. xviii. p. 94. thys (Pamphractus), with a new genus, — an as- 
§ A fine Holoptychius, very nearly akin to the semblage which shows that certain genera range 
H. nobilissimus of Perthshire, occurs in the up- from the Caithness flags, or central portion of the 
permost yellow sandstone of Dura Den. My late Old Eed group, up into its highest zone. Dr. 
friend the Eev. John Anderson, D.D. (well known Anderson's finest specimens are in the British 
by his work ' The Course of Creation '), detected Museum. 
