2 6 TRANSACTIONS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
plays conspicuous weakness. The Eurypterids and Cephalaspidians 
of the Upper Silurian are in evidence, but of the genera of Osteolepis^ 
Dipterus^ Tristichopterus^ Holoptychius^ and other fishes of the Old 
Red Sandstone, no undoubted plates or scales occur in the preceding 
formation. The question therefore arises, whence came these highly 
organised 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 Canadian formation, we have an 
equal right to know by what fresh-water pathway of distribution they 
were enabled to migrate 3000 miles between one point and another. 
Until a more satisfactory reply than we have yet seen is given to these 
questions, we shall assume that, in so far as the introduction and 
geological distribution of the fishes of the Old Red Sandstone are 
concerned, the “ lake ” theory is utterly inadequate to account for 
the one or the other. The simultaneous occurrence of ganoid fishes 
representing the same genera, and even the same species, in the for¬ 
mations of North America and Britain, and in the Devonian of 
Russia and other parts of Europe, undoubtedly points to a common 
source of origin and of geographical distribution, which is strikingly 
met by an adoption of the hypothesis of a boreal centre of origin, 
and a southward migration. In this way alone can we satisfactorily 
account for the adventitious appearance of the fishes of the Old Red 
Sandstone and Devonian. 
LAND PLANTS OF THE OLD RED SANDSTONE AND DEVONIAN. 
From the fact that land plants of the same genera and species 
occur in both the Old Red Sandstone and Devonian of Europe and 
North America, we are inclined to consider “plant evidence’’ as of 
but doubtful value. We should be prepared to find, in a marine for¬ 
mation, littoral deposits richer in plant remains than those of a 
deeper sea, and such appears to have been the order in which plant 
remains occurred. 
The formation of New Brunswick, Canada, is supposed to afford 
plants in greater number than elsewhere, yet Sir J. W. Dawson regards 
it as of estuarine origin. We show a specimen from Campbelltown, 
which, from the character of its matrix, and the contained crustacean 
remains, points to a marine origin. 
K7iorria and Palaeopteris hiberiiiais of the Old Red Sandstone of 
Ireland oecur in the Devonian of Cornwall; Sphenopteris^ Lepidode7i- 
dron^ Gaspia7ium^ and P. Jiiberniais^ are met with in the Devonian of 
Belgium and the north of France.* We also find in the Devonian 
of New York, Pennsylvania, and Ohio, numerous plants referable to 
* Sir A. Geikie, Textbook of Geol. 1882. Pages 700-702. 
