On the contrary, we have every reason to believe, from the study of the tertiary formations, that species and groups of species gradually disappear, one after another, first from one spot, then from another, and finally from the world.
Guk, aitzitik, tertziarioko formazioen azterketa bide, badugu oinarririk uste izateko espezieak eta espezie taldeak poliki-poliki desagertu egiten direla, bata bestearen ondoren, lehenengo leku batetik, gero beste batetik eta azkenean mundutik.