OLD RED SANDSTONE OF WESTERN EUROPE, A17 
we cannot fail to be struck by the close lithological resemblance of the rocks to 
those of some of the Caithness cliffs. Grey and reddish flaggy sandstone, with 
bands of red shale and dark grey flagstone in rapid alternation, give the same 
striped aspect to the mural faces of rock. Many of the beds also are strongly 
calcareous, and weather with the same pale surface and worn edges. A further 
resemblance to parts of the Caithness cliffs is found in the occasional sudden 
rise in the angle of inclination, owing to a local plication or a fault, as at the 
north-west promontory of Noss. 
The beds which form the southern part of Noss seem to be the highest parts 
of the Shetland Old Red Sandstone. They dip gently southwards ; but must 
rise again with a contrary inclination under the sea, for on the opposite side of 
the Noss Sound they form a range of cliffs on the east wall of Bressay, where 
the north-easterly dip of the beds is well seen. At the south end of that island 
another noble range of precipices affords an admirable section of the middle 
part of the series. Grey, thick-bedded, and flaggy sandstones, with here and 
there a prominent red band, rise into the Bard of Bressay and the Ord Head. 
Huge quadrangular buttresses, isolated as the rock splits off along its joints, 
stand out from the face of the cliff, and are here and there detached from it or 
united to it at the top, so as to form such striking features as the Giant’s Leg. 
Several sea-caves have been tunnelled into the cliffs. Of these the largest, 
known as the Orkneyman’s Cave, shows how strongly calcareous the strata 
must be, since its walls and roof are crusted and ribbed with stalagmite. 
At Sand Lodge grey flaggy sandstones, with bands of darker shaly flagstones, 
are brought down against the schist without the intervention of the basement 
conglomerates. Some of these strata, particularly the dark shaly layers, 
abound in plant remains. The opposite island of Mousa consists of similar 
| strata with the same fossils. Some of its beds are so strongly calcareous as 
to pass into an impure argillaceous limestone. At the extreme southern 
point of Shetland the cliffs of Sumburgh Head show fine grey micaceous 
sandstones and flagstones, with bands of conglomerate, which pass down west- 
| wards into a coarse conglomerate like that which flanks the eastern side of the 
hills north to Rovey Head. On the whole, the strata of the Shetland Old Red 
Sandstone are more arenaceous than those of the typical Caithness flags, but 
not more so than some portions of that series, particularly the older half of the 
| Wick flagstones, and the underlying sandy groups. 
3. Fossils.—As in Caithness, so in Shetland organic remains are not uniformly 
distributed. They occur least frequently in the sandy strata, most commonly 
in those which are shaly and calcareous, consequently the Shetland beds will 
probably never prove markedly fossiliferous. Some of the strata are so exactly 
like those which would have yielded fossils in Orkney and Caithness that they 
VOL. XXVIII. PART IL, 5 Q 
