Limacina (on which the whales feed); and 2.

Hyalea, a lovely little thing in a glass shell, which lives in the Mediterranean.
But since then strange discoveries have been made, especially by the naval officers who surveyed the bottom of the great Atlantic Ocean before laying down the electric cable between Ireland and America.

And this is what they found: That at the bottom of the Atlantic were vast plains of soft mud, in some places 2500 fathoms (15,000 feet) deep; that is, as deep as the Alps are high.

And more: they found out, to their surprise, that the oozy mud of the Atlantic floor was made up almost entirely of just the same atomies as make up our chalk, especially globigerinas; that, in fact, a vast bed of chalk was now forming at the bottom of the Atlantic, with living shells and sea-animals of the most brilliant colours crawling about on it in black darkness, and beds of sponges growing out of it, just as the sponges grew at the bottom of the old chalk ocean, and were all, generation after generation, turned into flints.
And, for reasons which you will hardly understand, men are beginning now to believe that the chalk has never ceased to be made, somewhere or other, for many thousand years, ever since the Winchester Downs were at the bottom of the sea: and that "the Globigerina-mud is not merely _a_ chalk formation, but a continuation of _the_ chalk formation, so _that we may be said to be still living in the age of Chalk_." {1} Ah, my little man, what would I not give to see you, before I die, add one such thought as that to the sum of human knowledge! So there the little creatures have been lying, making chalk out of the lime in the sea-water, layer over layer, the young over the old, the dead over the living, year after year, age after age--for how long?
Who can tell?
How deep the layer of new chalk at the bottom of the Atlantic is, we can never know.

But the layer of live atomies on it is not an inch thick, probably not a tenth of an inch.