388 MR JOHN S. FLETT ON 



Hugh Milleu, in his Cruise of the Betsy (1858), p. 358, narrates how, during his stay 

 in Kirkwall, he paid a visit to a quarry a few hundred yards to the east of the town, 

 where he observed numerous specimens of a species of Coccosteus, which he regarded as 

 the same as those he had received from the neighbourhood of Thurso (collected by 

 Robert Dick), and as certainly distinct from, and not merely young forms of, the common 

 Coccosteus decipiens (Agassiz). For these he extemporises the name of Coccosteus 

 minor. As no specimens of this fossil from Orkney were contained in his collection, 

 and no further material had been obtained from this locality for many years, the 

 accuracy of this observation remained open to some doubt, in spite of his careful identi- 

 fication. Unfortunately, these quarries are now practically worked out and deserted, 

 but I can remember, years ago, seeing in the stones of some old houses in Kirkwall, 

 which had evidently come from this quarry, great numbers of very minute specimens 

 of a Coccosteus. With the rediscovery of this species, however, these doubts in great 

 measure are removed ; and as I shall subsequently show, the horizon of these rocks in 

 the vicinity of Kirkwall is identical with that of the beds which in Rousay contain the 

 same fossils. Hence, there is every presumption that this is another locality in Orkney 

 for this species. 



In the extreme south end of South Ronaldshay, I found at Banks Geo further 

 examples of the same species, and as here they occur at no great distance from the Eday 

 sandstone series of this island, it would seem that the horizon is a somewhat higher one 

 than that in which it occurs in Rousay and in Kirkwall ; but as the island is traversed 

 by a number of faults, no very great reliance can be placed on any estimates of the 

 thickness of the intervening rocks. 



Here, then, we have from three localities — one in the north, one in the centre, and 

 one in the south of the county, the extreme stations being over thirty miles apart — the 

 occurrence of a distinct and characteristic fossil in the flagstones. With it occurs another 

 Thursius pholidotus (Traquair), which is nowhere known except accompanying it. 

 From the many quarries in the West Mainland, from which for seventy years innumer 

 able specimens have been obtained, not one case is known in which these have been 

 found, and it may safely be presumed that there they do not occur. Their absence, at 

 any rate, cannot be accounted for by imperfect preservation or insufficient search. They 

 may be assumed, in consequence, to constitute the type fossils of a zone of the Orcadian 

 Old Red Sandstone beneath that already defined for the Eday sandstones, and the beds 

 in which they occur I shall designate, from the locality in which the fossils are best pre- 

 served, the Rousay beds. 



List of the fossils contained in the Rousay beds of Orkney : — 



Thursius pholidotus (Traq.), Rousay. 



Coccosteus minor (Miller), Rousay, Kirkwall, S. Ronaldshay. 



Glyptolepis paucidcns (Ag.), Kirkwall, Rousay, Eday, Tankerness, Westray, Sanday, Evie, etc. 

 Dipterus valencienesii (S. and M.), Kirkwall, Tankerness, Rousay, Eday, Evie, Firth, Westray, 

 Sanday, etc. 



