For, as already said, according to the present chronological arrangement, many kinds of invertebrates, both terrestrial and marine, occurring in comparative abundance in our modern world, are found as fossils only in the very "oldest" rocks and are wholly absent from all the rest!!! Others which date from "Mesozoic times" are wholly absent from the Tertiaries, though abundant in our modern world. This I regard as another crucial test of the rationality of this idea of a life succession.
Of course there are certain limitations which must be borne in mind. If we find a series of beds made up largely of deep sea deposits, we cannot reasonably expect to find in them examples of all the land forms of the preceding "ages" which then survived, nor even of the shallow water types. Nor, conversely, can we demand that, in beds crowded with the remains of the great mammals and plants, and thus probably of fresh or shallow water formation, we ought to find examples of all the marine types still surviving. We now know that each level of ocean depth has its characteristic types of life, just as do the different heights on a mountain side. This doctrine of "rock facies" was, I believe, enunciated first in 1838. Edward Forbes also did much for this same idea, showing how at the present time certain faunas are confined to definite geographical limits, and particular ocean depths. Jules Marcou about 1848 applied this principle to the fossils and showed how such distinctions must have prevailed during geological time.
Here it seems that we are at last getting a refreshing breath of true science; but if carried out in its entirety how shall we assure ourselves that in the long ago very diverse types of fossils, e.g., gratolites and nummulites, or even trilobites and mammals, could not have been contemporary with each other? This principle of "rock facies," if incorporated into the science in its early days, would have saved the world from a large share of the nonsense in our modern geological and zoological text-books.
But in answer to any pleadings about the imperfection of the record, or any protests about the injustice of judging all the life-forms of an "age" by a few examples of local character, i.e., of fresh, shallow, or deep water as the case may be, the very obvious retort is, Why then are such local and fragmentary records given a time value? Why, for example, should the Carboniferous and associated formations be counted as representing all the deposits made in a certain age of the world, when we know from the Cambrian and Silurian and also from the alleged "subsequent" Jurassic that there must have been vast open sea deposits formed contemporaneously?
As Dana expresses it:
"The Lias and Oolyte of Britain and Europe afforded the first full display of the marine fauna of the world since the era of the Subcarboniferous. Very partial exhibits were made by the few marine beds of the Coal measures: still less by the beds of the Permian, and far less by the Triassic. The seas had not been depopulated. The occurrence of over 4,000 invertebrate species in Britain in the single Jurassic period is evidence, not of deficient life for the eras preceding, but of extremely deficient records."[44]
Surely these words exhibit the "phylogenic series" in all its native, unscientific deformity. It is because the Coal-measures, the Permian, and the Triassic, are necessarily "extremely deficient records" of the total life-forms then in the world, that I am writing this chapter, and this book. But it seems like perverseness to plead about the imperfection of the record, and yet refuse the evidently complementary deposits when they are presented. If, as this illustrious author says, "The seas had not been depopulated," what would he have us think they were doing? Were they forming no deposits all these intervening ages that the Carboniferous, Permian, and Triassic were being piled up? Were the fishes and invertebrates all immortalized for these ages, or were they, when old and full of days translated to some supermundane sphere, thus escaping deposit in the rocks? Did the elements continue in the status quo all these uncounted millions of years? and if so, how did they receive notice that the Triassic period was at last ended, and that it was time for them to begin work again? I do not like to appear trivial; but these questions serve to expose the folly of taking diverse, local, and partial deposits, and attaching a chronological value to each of them separately, and then pleading in a piteous, helpless way about the imperfection of the record.
And yet I cannot promise to present a tithe of the possible evidence, because of two serious handicaps. First, the ordinary literature of the science is silent and meagre enough in all conscience, even though the bare fact may be recorded that a "genus" of the Cambrian or Silurian is "closely allied" to some genus now living. It may be even admitted that "according to some it is not genetically distinct from the modern genus" so-and-so; but the authors never descend below the "genus," and in most cases forget to tell us whether or not it occurs in other "later" formations, though of course the presumption is that it does not, but has skipped all the intervening ages, or it would hardly be named as a characteristic type of the formation in which it occurs.
But this disadvantage, serious though it be, is scarcely worth speaking of when we remember the significant words of a well-known authority already quoted:
"Some geologists make it a point to give a new name to all forms found in the Palaeozoic rocks, i.e. a name different from those of modern species."