L. Agassiz on Animals in Geological Times. 317 
cal formations. But should we compare the fossil fishes of each 
geological period as they are known from a few localities, with 
the whole number of fishes which exist all over the world in our 
day? It would be as unphilosophical as it would be inconsistent 
With our knowledge of the geographical distribution of animals. 
Like all other living beings, fishes are located within definite 
boundaries, and it will be but fair to compare the fossil species of 
4given locality with the special Ichthyological faune which oc- 
cur in different oceans, or in different fresh-water basins. 
with this rule we may institute a comparison of the fossil fishes 
with the living ones, with reference to their number as well as to 
their variety. 
he number of species of fossil fishes known at present from 
the tertiary deposits, in a single spot, upon the Island of Sheppy, 
18 greater than the number of fishes which have been gathered 
around the coast of any of the islands of the Pacific Ocean, as 
far as we know the local Ichthyological faunze of those regions ; 
itis as great, nearly, as the whole number of fishes known from 
the shores of Great Britain. ‘The same may be said of the fishes 
Mount Bolea, or of Mount Lebanon, or of those of the white 
chalk of England, or of those of Solenhofen, or of those of the 
curs at the present day? So that it can be fairly said, that at all 
Periods, fishes have presented as great a variety of forms, and as 
numerous Species, as under corresponding circumstances at the 
da 
The class of Reptiles will allow similar conclusions, for though 
,.- slants of the class have chiefly been studied, do they not in- 
dicate an abundance, and a variety of these anima ing the 
Stcoxp Seams, Vol. XVII, No. 61.—May, 1854. 41 
