John o Groat’s Horizon of the Old Red Sandstone. — 255 
XXI. On the Discovery in Orkney of the John 0 Croat’s 
Horizon of the Old Red Sandstone. By JOHN 8S. FLEr?, 
M.B., B.Se., Assistant to the Professor of Geology in 
Edinbureh University. 
(Read 19th February 1896.) 
It is now four or five years since I discovered in a quarry 
in Deerness, in the East Mainland of Orkney, specimens of 
Dipterus macropterus (Traquair), a fish hitherto recorded 
only from the John o’ Groat’s beds in the north-east of 
Caithness. Last summer, when visiting the same quarry in 
the hope of obtaining additional specimens, I was struck by 
the presence of a small Asterolepid, which greatly resembled 
Microbrachius Dicki (Peach), another of the fishes hitherto 
peculiar to the above-mentioned horizon in Caithness. The 
specimens were not well preserved, but careful examination 
confirmed my first impression, and when I returned to 
Edinburgh I submitted them to Dr Traquair, who assured 
me of their identity. During a short holiday at Christmas 
I was enabled to revisit the locality and collect additional 
specimens of the fishes which occurred in it, as well as 
to make some examination of the strata of the district. 
Having shown the entire collection to Dr Traquair, he at 
once identified several of the specimens as belonging. to 
Trichistopterus alatus (Egerton), making three species in all 
which have been yielded by the beds exposed in this quarry. 
What is worthy of note is that these three species, now 
for the first time recorded from Orkney, are precisely those 
which are characteristic of the John o’ Groat’s beds in 
Caithness. The quarry is a small one, about 400 yards 
north of the Deerness Parish School. The rock is a dark 
erey, thin bedded, very calcareous and brittle flagstone. It 
dips E.S.E. at a low angle, and in many places shows a 
curious curving and contortion of the beds. In this quarry 
no other description of rock is to be seen. The fossils are 
exceedingly abundant, Dipterus muacropterus greatly pre- 
dominating in numbers. When I visited the quarry, the 
layer then being lifted showed on its exposed face quite 
