The development of the Earth and life on it represents for us - the children of the Earth - the most exciting spectacle that has ever been played out in the vastness of the Universe and which continues to this day. It takes place in an immeasurably long period of time, in which centuries and millennia can be compared with small grains of giant hourglass of eternity. This whole infinitely long period of time, from the beginning to the present day, is filled with tireless development, constant movement forward: it is full of continuous change and change. The face of the Earth was constantly changing, more and more living things were constantly created, the appearance of which was by no means accidental, but natural. Many of these creatures are long extinct. Nevertheless, they deserve our attention.