There are three great series of strata beneath the Silurian system in Canada, in the lowest of which the Eozoon is found.

Sir W.

Logan states that their "united thickness may possibly far surpass that of all the succeeding rocks, from the base of the palaeozoic series to the present time.

We are thus carried back to a period so remote, that the appearance of the so-called primordial fauna (of Barrande) may by some be considered as a comparatively modern event.