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, this Terebratulina has peacefully propagated its species from generation to generation, and stands to this day, as a living testimony to the continuity of the present with the past history of the globe.

Up to this moment I have stated, so far as I know, nothing but well-authenticated facts, and the immediate conclusions which they force upon the mind.

But the mind is so constituted that it does not willingly rest in facts and immediate causes, but seeks always after a knowledge of the remoter links in the chain of causation.

Taking the many changes of any given spot of the earth’s surface, from sea to land and from land to sea, as an established fact, we cannot refrain from asking ourselves how these changes have occurred.  And when we have explained them—­as they must be explained—­by the alternate slow movements of elevation and depression which have affected the crust of the earth, we go still further back, and ask, Why these movements?