This occurs in several parts of Canada, while the Laurentian rocks have evidently been subjected to metamorphism and long-continued weathering before the Lower Silurian were deposited; and in some cases the latter rest on weather-worn and pitted surfaces, and are filled with angular bits of the underlying rock, as well as with drift-shells which have been cast on these old Laurentian shores; while in other cases the Silurian rests on smooth water-worn Laurentian rocks, and is filled at the junction with well-rounded pebbles and grains of sand which have evidently been subjected to a more thorough attrition then those of the present beach. With respect to the line of division between the Primordial and the next succeeding rocks, it will be seen that important movements of the continents occurred at the close of the Cambrian, and in some places the Cambrian rocks have been much disturbed before the deposition of the Lower Silurian. Seated on some ancient promontory of the Laurentian, and looking over the plain which, in the Primordial and Lower Silurian periods was the sea, I have often wished for some shred of vegetable matter to tell what lived on that land when the Primordial surf beat upon its shore, and washed up the Trilobites and Brachiopods of those old seas; but no rock has yet taken up its parable to reveal the secret, and the Primordial is vocal only with the old story: "And God said, Let the waters swarm with swarming living things, and it was so." So our picture of the period may represent a sea-bottom swarming with animals of low grade, some sessile, some locomotive; and we may merely suppose a distant shore with vegetation dimly seen, and active volcanoes; but a shore on which no foot of naturalist has yet trod to scan its productions. Very different estimates have been formed of the amount of life in this period, according to the position given to its latest limit. Taking some of the more modern views of this subject, we might have included among the Primordial animals many additional creatures, which we prefer noticing in the Silurian, since it may at least be affirmed that their head-quarters were in that age, even if they had a beginning in the Primordial. It may be interesting here, however, to note the actual amount of life known to us in this period, taken in its largest scope. In doing this, I shall take advantage of an interesting table given by Dr. Bigsby,[G] and representing the state of knowledge in 1868, and shall group the species in such a manner as to indicate the relative abundance of distinct types of structure. We find then-- Plants (all, or nearly all, supposed to be sea-weeds, and some, probably, mere tracks or trails of animals) 22 species. Sponges, and similar creatures 27 " Corals and their allies 6 " Starfishes and their allies 4 " Worms 29 "