thus, while the differences between the living creatures
of the time before the chalk and those of the present day appear
startling, if placed side by side, we are led from one to the other by
the most gradual progress, if we follow the course of Nature through
the whole series of those relics of her operations which she has left
behind.

And it is by the population of the chalk sea that the ancient and the
modern inhabitants of the world are most completely connected. The
groups which are dying out flourish, side by side, with the groups which
are now the dominant forms of life.

Thus the chalk contains remains of those strange flying and swimming
reptiles, the pterodactyl, the ichthyosaurus, and the plesiosaurus,
which are found in no later deposits, but abounded in preceding ages.
The chambered shells called ammonites and belemnites, which are so
characteristic of the period preceding the cretaceous, in like manner
die with it.

But, amongst these fading remainders of a previous state of things,
are some very modern forms of life, looking like Yankee pedlars among
a tribe of Red Indians. Crocodiles of modern type appear; bony fishes,
many of them very similar to existing species almost supplant the forms
of fish which predominate in more ancient seas; and many kinds of living
shellfish first become known to us in the chalk. The vegetation acquires
a modern aspect. A few living animals are not even distinguishable as
species, from those which existed at that remote epoch. The Globigerina
of the present day, for example, is not different specifically from that
of the chalk; and the same may be said of many other Foraminifera. I
think it probable that critical and unprejudiced examination will show
that more than one species of much higher animals have had a similar
longevity; but the only example, which I can at present give confidently
is the snake's-head lamp-shell (Terebratulina caput serpentis), which
lives in our English seas and abounded (as Terebratulina striata of
authors) in the chalk.

The longest line of human ancestry must hide its diminished head before
the pedigree of this insignificant shell-fish. We Englishmen are proud
to have an ancestor who was present at the Battle of Hastings. The
ancestors of Terebratulina caput serpentis may have been present at a
battle of Ichthyosauria in that part of the sea which, when the chalk
was forming, flowed over the site of Hastings. While all around has
changed,