68 THE OLD RED SANDSTONE. 
Malacopterygil, or soft-finned order of Cuvier —an order to 
which all these well-known fish, with an immense multitude 
of others, belong. Thus the results of the principle of classi- 
fication adopted by Agassiz wonderfully agree with the re- 
sults of the less simple principles adopted by Cuvier and the 
other masters in this department of Natural History. Now, 
it is peculiar to yet a fourth order, the Ganoidean, or shining- 
scaled order, that by much the greater number of the genera 
which it comprises exist only in the fossil state. At least 
five sixths of the whole were ascertained to be extinct several 
years ago, ata time when the knowledge of fossil Ichthyology 
was much more limited than at present: the proportions are 
now found to be immensely greater on the side of the dead. 
And this order seems to have included all the semi-osseous, 
semi-cartilaginous ichthyolites of the Lower Old Red Sand- 
stone: the enamelled scale is the characteristic, according to 
Agassiz’s principle of classification, of the existences that 
filled the gap so often alluded to- as existing in the present 
creation. All their scales glitter with enamel: they bore to 
this order the relation that the cartilaginous fish bear to the 
Placoidean order, the thorny-finned fish to the Ctenoidean 
order, and the soft-finned fish to the Cycloidean order. It 
also included, with the semi-cartilaginous, the sauroid fish — 
those master existences and tyrants of the earlier vertebrata ; 
and both classes find their representatives among the com- 
paratively few ganoid fishes of the present creation ; the one 
in the sturgeon family, which of all existing families ap- 
proaches nearest in other respects to the extinct semi-carti- 
laginous fishes ; the other in the sauroid genus Lepzdosteus, to 
which the bony pike belongs. The head, back, and sides of 
the sturgeon are defended, as has been already remarked, by 
longitudinal rows of hard osseous bosses—the bony pike is 
