I will now give a few examples to illustrate these remarks; and to
show how liable we are to error in supposing that whole groups of
species have suddenly been produced. I may recall the well-known fact
that in geological treatises, published not many years ago, the great
class of mammals was always spoken of as having abruptly come in at
the commencement of the tertiary series. And now one of the richest
known accumulations of fossil mammals belongs to the middle of the
secondary series; and one true mammal has been discovered in the new
red sandstone at nearly the commencement of this great series. Cuvier
used to urge that no monkey occurred in any tertiary stratum; but now
extinct species have been discovered in India, South America, and in
Europe even as far back as the eocene stage. The most striking case,
however, is that of the Whale family; as these animals have huge
bones, are marine, and range over the world, the fact of not a single
bone of a whale having been discovered in any secondary formation,
seemed fully to justify the belief that this great and distinct order
had been suddenly produced in the interval between the latest
secondary and earliest tertiary formation. But now we may read in the
Supplement to Lyell's 'Manual,' published in 1858, clear evidence of
the existence of whales in the upper greensand, some time before the
close of the secondary period.
I may give another instance, which from having passed under my own
eyes has much struck me.
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