ON THE AGE OF THE OLD RED SANDSTONE OF SHETLAND. 317 



Caithness (35) and the Upper Old Red of Canada (36). Coccosteus also is known from the 

 whole range of the Devonian or Old Red Sandstone succession (19). It is easy, however, 

 to exaggerate the importance of exceptional cases. More important is the fact that 

 Asterolepis is represented by a species as yet undescribed in beds immediately under- 

 lying the John o' Groats zone of the Orcadian Old Red in Orkney (4). This indicates 

 that if the Shetland beds be Upper Old Red, they have close relationships to the 

 Orcadian. Similarly, there are grounds for believing that the Nairn beds (18) which 

 contain Asterolepis are older than the Elgin, Dura Den, Jedburgh, and Kiltorcan 

 Sandstones, in which Bothriolepis and Holoptychius nobilissimvs occur. The latter 

 must represent the highest portion of the Old Red Sandstone, as in places they pass 

 up conformably into the base of the Carboniferous. 



The only other animal remains as yet obtained from the Shetland Old Red Sandstone 

 are Estheria membranacea (Pacht) and plant fragments. Of these, the former was first 

 recorded by Sir R. Mukchison (22), and was described by Professor Rupert Jones (31). 

 This species is abundant and well preserved in the Orcadian Old Red of Caithness and 

 Orkney. It occurs also in the Devonian of Livland (Livonia) in Russia, but has not 

 been found in the Upper Old Red Sandstone of any part of Great Britain (except 

 Shetland). This is sufficient to indicate that the Shetland beds have close relationships 

 with the Middle Old Red Sandstone. 



The Fossil Flora of the Shetland Old Red Sandstone. 



The fossil plants found near Lerwick have been described by many palseobotanists. 

 They are in a most unsatisfactory state of preservation, but (with the exception of Sir 

 Joseph Hooker) (15) all who have examined them have noted their resemblance to the 

 hardly less imperfect plant-remains so numerous in the Middle Old Red of Caithness and 

 Orkney. Recognising that little was definitely known about their real nature, I had 

 specimens forwarded to Dr Kidston, in order to obtain the latest and most authoritative 

 opinion regarding them. He assures me that, whatever may be their botanical affinities, 

 they have nothing in common with the Lower Old Red flora of Forfarshire and Perth- 

 shire, or the Upper Old Red floras of Kiltorcan and Roxburghshire. So far as they are 

 determinable, they resemble rather the plants of the Orcadian Old Red. This opinion, 

 though vague, is of value, as confirming the evidence provided by the crustaceans 

 (Estheria) and one of the genera of fishes (Asterolepis). 



LlTHOLOGY. 



The lithological similarity between the Old Red Sandstone of Shetland and that of 

 Caithness and Orkney has been remarked on by various writers. It is best seen in the 

 cliff exposures when viewed from a distance, as the thin-bedded flags of Bressay and 

 Noss, where eroded by the sea, yield cliffs very like those of Orkney. Closer examination, 



