on THE OLD RED SANDSTONE. 
in a sea gradually shallowing, and out of which the land had 
already partially emerged. 
A continuous ocean spreads over the space now occupied 
by the British islands: in the tract covered by the green 
fields and brown moors of our own country, the bottom, for 
a hundred yards downwards, is composed of the debris of 
rolled pebbles and coarse sand intermingled, long since con- 
solidated into the lower member of the Old Red Sandstone ; 
the upper surface is composed of banks of sand, mud, and 
clay ; and the sea, swarming with animal life, flows over all. 
My present object is to describe the inhabitants of that sea. 
Of these, the greater part yet discovered have been named 
by Agassiz, the highest authority as an ichthyologist in 
Europe or the world, and in whom the scarcely more cele- 
brated Cuvier recognized a naturalist in every respect worthy 
to succeed him. ‘The comparative amount of the labors of 
these two great men in fossil ichthyology, and the amazing 
acceleration which has taken place within the last few 
years in the progress of geological science, are illustrated 
together, and that very strikingly, by the following interesting 
fact — a fact derived directly from Agassiz himself, and which 
must be new to the great bulk of my readers. When Cuvier 
closed his researches in this department, he had named and 
described, for the guidance of the geologist, ninety-two distinct 
species of fossil fish ; nor was it then known that the entire 
geological scale, from the Upper Tertiary to the Grauwacke 
inclusive, contained more. Agassiz commenced his labors ; 
and, in a period of time little exceeding fourteen years, he 
has raised the number of species from ninety-two to sixteen 
hundred. And this number, great as it is, is receiving acces- 
sions almost every day. In his late visit to Scotland, he found 
eleven new species, and one new genus, in the collection of 
