. - OL 
———— 
OLD RED SANDSTONE OF WESTERN EUROPE. 425 
erupted as a lava during the formation of the Old Red Sandstone of this valley. 
A peculiar interest attaches to it therefore ; for if this be truly its history, it is 
the only interbedded volcanic mass yet discovered on the mainland of Scot- 
land, to the north of the Grampian barrier.* 
The Rhynie or Quarry Hill Sandstones have long been worked, and are well 
exposed in the quarries to the south of Muir of Rhynie. A good section has 
likewise been cut through the lower portion by the Burn of Craig. One of 
their most obvious features is the great number and variety of the clay-patches 
above mentioned. Many of them so closely resemble worm-burrows that, if 
found alone, they could hardly fail to be regarded as such. But they are asso- 
ciated with, and indeed pass into, others of the most irregular branching shapes, 
sometimes clustered in bunches, or dwindling into flattened leaf-like ribbons, 
which rather suggest a vegetable origin. The red clay of these concretions is 
sharply defined from the surrounding pale grey sandstone, and as they are 
singularly abundant in some of the beds, they give a very striking character 
to the rock. The general colour of the sandstones is pale grey, inclining 
now to a dirty green, now to a pale purple, with many dark-red and purple 
blotches, besides the pellets, pipes, and branching threads and stems of red 
clay. Some of the beds are well ripple-marked. Neither my companion 
nor I could observe any fossils, though the Rev. A. Mackay found there 
in 1854 some organic remains, among which one was stated by Sir R. 
Morcutson to be “unquestionably a fragment of a large stem of a plant, 
which measures 4 feet in length by 5 inches in breadth. It is nearly cylindrical, 
and is fluted irregularly near the pointed tip. No joints or nodes are visible, as 
in Calamites ; but the surface is coarsely striated. The striz or ribs are too 
obscure to warrant us in placing this fossil plant in the genus Coluwmnaria of 
STERNBERG, which it most resembles.” His description seems to point to the 
wide-spread “corduroy” stems of Shetland. Some of the other markings on 
these Rhynie sandstones were regarded by Hucu Minter as the tracks of 
crustaceans. “ An inspection of these very imperfect impressions conveyed to 
Mr Satter the idea that they might have been made by the pectoral fins of 
fishes swimming in shallow water.”+ 
The highest visible strata of the district occur on the west side of the 
Quarry Hill, and consist of green and grey sandy and calcareous shales. No 
fossils were observed in them, but they might be searched with some prospect 
of yielding plants and fish remains. They resemble some of the strata seen in 
the valley of Nairn, about Clava, like which they remind one of the so-called 
“calmy ” shales in the Cement-Stone series of the Lower Carboniferous rocks 
| of central Scotland. 
* Since this was written another volcanic locality has been found. See p. 435, note. - 
| * Mourcuison, “ Quart. Journ, Geol. Soc.” xv. 432. 
| VOL. XXVIII. PART II. aS 
