On the Old Red of Scotland. 219 



fishes of the Old Red Sandstone ? More especially, from what 

 fresh- water region did they migrate? Not only so, but as the 

 same genera of fishes occur in the Devonian of North America 

 and the St. Lawrence basin, we have an equal right to know hy 

 what fresh-water pathway of distribution they were enabled to 

 migrate some 3000 miles between one point and another. 1 



But so far as these questions are concerned, the advocates of the 

 " Lake theory " have maintained an ominous silence. Some eminent 

 palseobotanists have advocated the view of an Arctic origin and 

 southward migration of the flora of the globe ; while Dr. A. Wallace 

 also believes " in the northern origin of both the fauna and the 

 flora of the world." 3 The simultaneous occurrence of ganoidian 

 fishes of the same genera and species in the formations of North 

 America and Britain, and in the Devonian of Russia and Central 

 Europe, seems also to indicate a boreal origin and southward migration 

 of the fishes of the Old Red Sandstone. In this connection the 

 genus Acanthaspis (Newberry), of the Devonian of Ohio, is of 

 especial interest. A specimen of this fish from the Lower Devonian 

 of Spitz bergen is figured and described by Mr. Smith Woodward, 3 

 while Dr. R. H. Traquair mentions its occurrence in the Lower 

 Devonian of Priim in the Eifel. 4 These discoveries thus show an 

 extremely wide range for this Placoderm of the Devonian. 



Stratigraphical and Biological Comparisons. 



We find Sir A. Geikie stating that no unequivocally marine fossil 

 remains occur in the Old Red Sandstone. 5 We believe we are correct 

 in assuming that our author refers to the fishes and crustaceans 

 alike as equivocally marine remains. We have, however, seen no 

 reason assigned why Eurypterids and Placoderms of the same 

 genera, which are marine in the later Upper Silurian, and fishes of the 

 bame genera and species, which are equally marine in the Devonian 

 of Russia and Central Europe, as well as in the Devonian of North 

 America, should be termed equivocally marine in the Old Red 

 Sandstone. But further, Sir A. Geikie refers to the occurrence, in 

 the heart of the Old Red Sandstone of Lanarkshire, of a band of 

 rock about 5000 feet above the base of the system, containing true 

 Silurian fossil remains, whose occurrence he attributes to an irrup- 

 tion of an outside sea of Silurian character. 6 



The Evidence derived from Fossil Plant-Remains. 



It has been frequently assumed that the presence of land plants 

 in the Old Red Sandstone is a proof of its fresh-water origin. But 

 from an a priori point of view, no good reason can be assigned 

 against the occurrence of land plants in either the sea, on the one 

 hand, or in inland lakes, on the other. As a matter of fact, plant- 

 remains occur indifferently in the Old Red Sandstone and Devonian. 



1 Proc. Perthshire Soc. Nat. Sci. 1893-4. 



2 Brit. Assoc. Address by Sir J. D. Hooker, 1881. 



3 Nat. Science, vol. i, No. 8, p. 602. 



* Ann. and Mag. Nat. Hist, sec. 6, vol. xiv, p. 370. 

 6 "Textbook of Geology," 1882, p. 706. 

 6 Ibid., p. 714. 



