402 Q. Hickling — Old Red Sandstone of Forfarshire. 



The paloeontological evidence was fully appreciated by Murchison 

 (1859) and Salter (Salter, 1863), who based their conclusion that the 

 fossiliferous horizons of Caithness were higher than those of Forfarshire 

 on a comparison with the continental Devonian and Old lied rocks, as 

 is so well known. That conclusion is now greatly strengthened by 

 the patient work of Traquair, who regards the question rather from 

 the biological side. From that view, the evidence may perhaps 

 best be summarised thus : The fishes of the Orcadian Old Red are 

 undoubtedly more nearly allied to those of the Upper Old Red than 

 are those from the Caledonian rocks ; while, on the other hand, the 

 Forfarshire fossils bear a much greater similarity to those of the 

 highest Silurian beds than do those of Caithness. These facts, then, 

 fully bear out the conclusion of Murchison and Salter. Goodchild 

 vigorously advocated this view in a paper written shortly before his 

 lamented death (Goodchild, 1904), and, for a fuller analysis of the 

 palseontological data, reference may be made to the exhaustive account 

 by Evans (Evans, 1891). As this latter paper may not be readily 

 accessible, it may be stated that lie finds that of the thirty species of 

 fish in the Orcadian Old Red, six occur in the lJi)per Devonian of 

 Russia. A single species is voiy doubtfully common to the Forfarshire 

 rocks. Of the eighteen genera, ten occur in the Upper Devonian or 

 Upper Old Red. One genus is common to the Lower Old Red, and 

 two others veiy doubtfully so. I think it may safely be added that 

 the work done since. 1891 has at least fully confirmed this distinctness 

 of the Caledonian and Orcadian faunas (Home, 1901). 



Two points thus seem clear : it is physically impossible that the 

 two areas of Old Red under consideration could have been entirely 

 deposited separately, yet the faunas are entirely distinct, and the 

 nature of the faunal difference is such as to indicate that the Orcadian 

 fossil-beds are higher than the Caledonian. In other words, the 

 fossiliferous deposits of Caithness must be superposed on those of 

 Forfarshire. But that is quite a different matter to saying that 

 16,000 feet of Old Red in the north must be superposed on 

 20,000 feet in the south. In Caithness the lowest 4,000 feet or so 

 appear to be xinfossiliferous, or practically so (lower part of Wick 

 group, below Achanarras, and the lower Sandy and Conglomeratic 

 groups), and hence 12,000 feet will be a liberal estimate for the 

 thickness, which includes all the fossiliferous horizons, even on 

 Geikie's estimate, which Evans, in the paper referred to, considers too 

 great. In Forfarshire I have pointed oiit that the fossil-bearing 

 strata are confined to the Cairnconnan and Carmyllie series, with 

 a combined thickness of certainly under 4,000 feet. Hence 16,000 feet 

 will be a generous estimate of the united thickness of the fossiliferous 

 beds of the two areas. The 4,000 or 5,000 feet above the highest 

 fossil-bearing zone in Forfarshire and the 4,000 below the lowest in 

 Caithness count for nothing. 



It will be remarked that there is still some 6,000 or 7,000 feet 

 of strata below the fossiliferous band in Forfarshire to be dealt with. 

 Regarding these I would say that as they have as yet yielded no 

 fossils it is impossible to say definitely what their age may be, except 

 in relation to the beds above. 



