Charles Lyell, Historian of Time's Cycle - Time's Arrow, Time's Cycle: Myth and Metaphor in the Discovery of Geological Time - page 139

their remains to later strata even if they had actually lived at modern
abundances in Paleozoic times.
Lyell could not evoke the same argument for mammals—since their dense
and massive bones fossilize more easily. He therefore invoked two biases of
discovery to argue that Paleozoic mammals abounded, but have not yet been
found as fossils. Our explorations have been largely restricted to Europe and
North America, a small segment of the globe. This region was the center of
an ocean during the Paleozoic, far from any continent that might yield a
floating carcass to full fathom five. After all, we might dredge an equally
large area of the central Pacific today, and find no signs of mammalian life:
The casualties must be rare indeed whereby land quadrupeds are swept by
rivers and torrents into the sea, and still rarer must be the contingency of such
a floating body not being devoured by sharks . . . But if the carcass should
escape and should happen to sink where sediment was in the act of
accumulating, and if the numerous causes of subsequent disintegration
should not efface all traces of the body included for countless ages in solid
rock, is it not contrary to all calculation of chances that we should hit upon
the exact spot—that mere point in the bed of the ancient ocean, where the
precious relic was entombed? (I, 149)
But Lyell's trump card was an empirical discovery, not a verbal argument.
Thirty years before, the fossil record of mammals had provided even better
signs of apparent progress—for their remains had been entirely confined to
the latest, or Tertiary, rocks. None had been found throughout the entire
middle realm, now called Mesozoic and popularly known as the age of
dinosaurs. But, by 1830, a few small mammals had been discovered in the
midst of Mesozoic strata. If the Mesozoic had fallen to assiduous exploration,
could the older Paleozoic rocks be far behind?
Second argument. Perhaps advanced vertebrates really did not live during the
early ages of fishes and primitive reptiles, but their