The simple facts that species have to be moved backwards and forwards between the amorphozoic and zoophytic groups, that relics may pass for fish in one year and sponges in another, and by-and-by be recognised again as fish, show the often imperfect condition of the record, even where it is not a complete blank. Where direct evidence of any kind is still unavailable, it may possibly be said that no sponges are found for such and such a period, because none existed in it. The plausibility of such an opinion can only be tested in fresh illustrations of the general argument. The coalfield of Nova Scotia has been described by Professor Dawson of Montreal. As it afforded a fine field for the exertions of the geologist, so it repaid him by its great richness in the fossil remains of plants. But in the coal formations of England and of Westphalia insects also had been found of different genera in addition to plants, while Nova Scotia, with all its vegetable wealth, yielded the anxious explorer but a single specimen of the still more interesting relics. That specimen consisted of the head and some other fragments of a large insect, probably neuropterous. That single specimen Professor Dawson tells us he found in a coprolite, in the fossil excrement of a reptile enclosed in the trunk of an erect sigillaria. Could any one invent a more curious cabinet to preserve so fragile a specimen for millions of years? Can it in this case be argued, that of insect remains nothing was found in the carboniferous of Nova Scotia but the head and some other appurtenances of a single neuropterous insect, because that head and those appurtenances were all that had ever flourished there? It cannot so be argued, not only because the analogies of the carboniferous formation in other parts of the world are conclusive against such argument, but also because within the last three or four years, after long and diligent search, two more species have been added to the collection of carboniferous insects from Nova Scotia itself. Two delicate wings, one very large and one small, have been found, each sealed, as it were, with a fern-leaf; each a frail but enduring record of life that must once have been brilliant and abundant[60].