ON THE AGE OF THE OLD RED SANDSTONE OF SHETLAND. 315 



A. Geikie's relegation of them to the Lower division of the system (which, of course, 

 included the Orcadian). In this opinion they were supported by C. W. Peach (27), who 

 re-examined the fossil plants described by Hooker, and found that they exhibited close 

 affinities to those obtained in the Old Red of Caithness and Orkney. 



In 1898, after spending part of several years in investigating the Old Red Sandstone 

 of Orkney (3), I determined to visit Shetland and make a search for fossil fishes which 

 would establish the position of the sandstones and shales of these islands relatively to 

 those of Caithness and Orkney. Six weeks were spent in a scrutiny of all the best ex- 

 posures on the east side of the mainland from Sumburgh Head to Lerwick, and in the 

 islands of Bressay and Noss. The results, though unsatisfactory, were not entirely dis- 

 appointing, as indecipherable fragments of fishes were obtained in Bressay, at Lerwick, 

 Sandwick, and the east side of Quendale Bay. Further search was determined on ; and 

 to meet the expenses of quarrying, a grant was applied for from the Royal Society of 

 London (Government Grant Committee), which was conceded. Consequently, in 1899, 

 with the consent of the late Mr Hamilton, of Unst, an opening was made in the beach 

 on the east side of Cullingsburgh Voe in Bressay, and our expectations were soon con- 

 firmed by the discovery of scattered plates of undoubted fossil fishes belonging to new 

 species. These fishes were handed to Dr Traquair for identification, and a preliminary 

 notice was inserted in Nature to announce the discovery of a new zone of the Old Red 

 Sandstone of Scotland (24). 



The Fish-bearing Beds of Bressay, and their Position in the Old Red 



Sandstone of Shetland. 



As recognised by all who have described this area, the structure of the district around 

 Lerwick and Bressay is exceedingly simple. A little west of Lerwick, coarse conglomerates 

 are faulted against the metamorphic series. They dip towards the east, and are succeeded 

 at the town of Lerwick by reddish and grey sandstones, often current-bedded, and 

 sometimes containing large rounded pebbles of quartzite, granite, etc. At the point 

 south-east of Lerwick known as the Nabb, grey micaceous sandstones occur, full of plant- 

 remains, and containing also the small crustacean Estheria membrancea (22). On the 

 opposite shore of Bressay Island the first beds met with are brownish and grey sand- 

 stones, often conglomeratic, and sometimes brecciform, with occasional grey and reddish 

 shales. A series of faults or crush belts run nearly north and south along this side of 

 the island from Maryfield to Ham, setting the beds frequently on end, and converting 

 them into breccias and crush conglomerates. In crossing Bressay the dip of the rocks 

 is consistently east or south-east, varying from ten to thirty degrees. The commonest 

 rocks are grey, micaceous, thin-bedded sandstones, with coarser, less micaceous, gritty 

 seams, often current-bedded. The sandstones contain rounded clay galls, and their sur- 

 faces are often covered with blackened fragments of plants and shreds of fine shale. Small 

 faults are frequently seen in the coast sections, mostly running parallel to the strike. On 



