THE OLD RED SANDSTONE OF THE ORKNEYS. 389 



Homosteus Milleri (Traq.), Kirkwall, Firth, Eousay, Westray, Sanday, Tankerness. 



Cheiracanihus Murchisoni (Ag.), Shapinshay. 



Coccosteus decipiens (Ag.), Deerness, Tankerness, Kirkwall, S. Ronaldshay. 



Osteolepis macrolepidotus (Ag.), Kirkwall, Deerness. 



Diplopterus Agassizi (Traill), Toab. 



Estheria membranacea, Kirkwall, Kendall, Westray. 



Asterolepis, sp. nov., Holm, Deerness, S. Ronaldshay. 



The Stromness Beds. — A careful examination of the list above given will show that 

 not only does it include certain fossils new or rare to Orkney, but that certain others 

 well known to occur there are wanting. It may be said that practically all the fossils 

 in the museums of the world or in private collections which have been furnished by 

 the Orkney flagstones come from a restricted district in the West Mainland, and in the 

 vicinity of the town of Stromness. Here the richness in fossil remains, and their fine 

 preservation, is in striking contrast to the Rousay beds which occupy the remainder of 

 the county. And not only are the fossils more numerous, but species occur which 

 have never been obtained from other districts. Of these, there are two species of 

 Pterychthys — P. Milleri (Ag.) and P. productus (Ag.) — Cheirolepis Trailli (Ag.), 

 Diplacanthus striatus (Ag.), and Gyroptychius angustus (M'Coy). These, then, in turn 

 constitute the type fossils of still another zone of the Old Eed of Orkney, which from 

 the locality of their typical development we will call the St7-omness beds. With them 

 others occur which are present also in the Rousay beds, viz. — 



Coccosteus decipiens (Ag.). 



Homosteus Milleri (Traquair). 



Dipterus valencienesii (Sedgw. and Murch.). 



Osteolepis macrolepidotus (Ag.). 



Diplopterus Agassizi (Traill). 



Cheiracanthus Murchisoni (Ag.). 



No value attaches to these latter as zone fossils, while there can be no doubt 

 that the former, or some of them at any rate, are entitled to this rank. Much remains 

 to be done before the knowledge of the distribution of the various fossil fishes in the 

 Orcadian Old Red Sandstone can be said to be complete, but, from the Stromness beds 

 at any rate, we have the result of seventy years of the activity of collectors, and the 

 main facts must be regarded as already sufficiently established. That in no case have 

 the type fossils of the Rousay beds been obtained in this locality is perfectly certain, 

 and is a striking fact when we remember that the present writer has obtained these 

 species from two localities in other parts of the county (South Ronaldshay and Rousay) 

 in the course of a short space of time ; while in no place have the type fossils of the 

 Stromness beds been obtained along with those of the Rousay beds, or, for that matter, 

 in any locality in which, according to the geological structure of the county, these 

 latter are present ; and further, as will be subsequently shown, these results, obtained 

 from a study of the distribution of the fossil fishes of Orkney alone, are in substantial 



