OLD RED SANDSTONE OF WESTERN EUROPE. 437 
thickness of a few feet. It seems to have been accumulated in a great bay, like 
the conglomerate of Cawdor to be immediately referred to. 
3. From the Spey to the Nairn. The two divisions of Old Red Sandstone in 
Morayshire-—Between the conglomeratic series which I have described as 
stretching in an interrupted course from Gamrie to the Spey, and the conglo- 
merates which lie immediately to the west, and are interstratified with bright 
red and yellow or grey Holoptychius-bearing sandstones, there is often too little 
lithological difference to allow of their being at once and by the eye distinguished 
from each other. When we consider that they have both been formed from 
similar materials, apparently under very similar conditions, and that the later 
conglomerates indeed have probably been more or less derived from the waste 
of the older masses, we need not be surprised that there should be difficulty in 
drawing a line of boundary between them. Such a line cannot be altogether 
satisfactorily traced until the ground is carefully mapped out in the minutest 
detail. 
In the meantime, however, we shall probably not err in classing with the 
great brecciated conglomerate of the Spey, as a part of the Caithness flag series, 
the similar rock which partially fills the ancient hollow of the vale of Rothes. 
It is a loose, incoherent, rudely stratified deposit like that of the Spey ravines, 
but with many well-rounded stones scattered through the sub-angular and 
angular detritus of quartz-rock, gneiss, schist, and other metamorphic rocks. 
These underlying masses appear here and there on both sides of the valley, 
which is thus of as early a date as the time of the Old Red Sandstone. After 
forming a marked feature on the east side of the valley, the conglomerate is 
succeeded below Coleburn’s Mill by the pebbly red, green, and grey sandstones, 
and green and red conglomerates of the well-known Scat Craig. 
In his memoir on the sandstones of Morayshire* (1858), Sir R. Murcuison, 
while describing the sections to the south of Elgin, which had been so well 
worked out by the Rev. Dr Gorpon, of Birnie, speaks of the Scat Craig con- 
glomerate as affording geological evidence of a transition from the Caithness 
flags into the Upper Old Red Sandstone, there being here, he affirms, “a union 
in this one mass of conglomerate of genera which in other places mark the 
central and upper members of the series.” He remarks that “the interest 
which specially attaches to the fossil fishes found at Scat Craig, is that whilst 
the Pterichthys major and other species of that genus, as well as the Asterolepis, 
are common to Caithness and the west of Moray (Lethen Bar, Clune, Altyre, &c.), 
there are other forms such as the Dendrodus latus and D. strigatus, Lamnodus, 
and Cricodus, which as well as the Asterolepis Asmusii, are common in the Old 
* “Quart. Journ. Geol. Soc.” xv, p. 425. 
VOL. XXVIII. PART II, iex 
