And leaving Hans to his work we started off together. The space between the water and the foot of the cliffs was considerable. It took half an hour to bring us to the wall of rock. We trampled under our feet numberless shells of all the forms and sizes which existed in the earliest ages of the world. I also saw immense carapaces more than fifteen feet in diameter. They had been the coverings of those gigantic glyptodons or armadillos of the Pliocene period, of which the modern tortoise is but a miniature representative. 14 The soil was besides this scattered with stony fragments, boulders rounded by water action, and ridged up in successive lines. I was therefore led to the conclusion that at one time the sea must have covered the ground on which we were treading. On the loose and scattered rocks, now out of the reach of the highest tides, the waves had left manifest traces of their power to wear their way in the hardest stone.