424 MR JOHN S. FLETT ON THE OLD RED SANDSTONE OF THE ORKNEYS. 



To these Dr Traquair adds two — Osteolepis macrolepidotus (Ag.), which certainly 

 occurs in the East Mainland of Orkney, and Diplopterus Agassizi (Traill), which, 

 he says, he has not been able to establish with certainty as a member of the Thurso 

 group. If we except the rare Palceospondylus Gunni (Traq.), which is known only 

 from Achanarras, we have three genera and six species which, so far as our present 

 knowledge of the distribution of the fossil fishes of the Scottish Old Red Sandstone 

 goes, may serve as type fossils for this group of rocks ; and these, it will be remembered, 

 are the genera which I found in Orkney to characterise the Stromness beds ; and we may 

 regard it as established that this is a distinct zone of the Orcadian Old Red Sandstone, 

 of which the representatives are the sandstones of Cromarty, Lethen, Gamrie, Clunie, 

 and Tynet, the flagstones of Achanarras in Caithness, and the Stromness beds of the 

 Orkneys. 



In conclusion, I wish to acknowledge my indebtedness to those who have assisted 

 me in this work — to Professor James Geikie, D.C.L., LL.D., F.R.S., without whose 

 encouragement and advice it would never have been undertaken ; to Dr R. H. Traquair, 

 LL.D., F.R.S., who has determined for me all the more important specimens collected, 

 and has kindly undertaken the description of the new material which turned up in the 

 course of the investigation ; to Messrs Benjamin Peach. F.R.S., and John Horne, F.G.S., 

 of the Geological Survey of Scotland, who have at all times placed at my service their 

 great knowledge of field work, and their intimate acquaintance with the geology of 

 the district. Mr James W. Cursiter, F. S.A.Scot., of Kirkwall, kindly placed at ray 

 disposal his fine library of books relating to the county, and his collection of Orkney 

 fossils ; Mr Thomas M'Crie, of Kirkwall, allowed me also to examine his collection ; and 

 Mr Magnus Spence, of Deerness, gave me most valuable assistance in the field work in 

 that district and elsewhere. 



