"The absence of Lamellibranchs in the Middle Cambrian, although present in both Lower and Upper, means the absence of fossils from the rocks, not of species from the faunas."
He puts this in italics by way of emphasis, for it is certainly a reasonable idea, and as A. R. Wallace says, "no one now doubts that where any type appears in two remote periods it must have been in existence during the whole intervening period, although we may have no record of it."[51] But what would be the result if we only extend this idea to its logical conclusion? It seems to be an effort to avoid one of the absurdities of the onion-coat theory, without, however, discarding that theory altogether.
In speaking of some corals and crinoids of the Devonian which "were absent" from some of the divisions of this formation because the conditions of the seas about New York "were unfavorable," Dana says that "they were back when the seas were again of sufficient purity."[52]
In his review of these formations he enlarges on this subject:
"At the close of the early Devonian the evidences of clear seas—the corals and crinoids, with most of the attendant life—disappear, migrating no one knows whither.... With the variations in the fineness, or other characteristics of the beds as H. S. Williams has illustrated, the species vary.... The faunas of each stratum are not strictly faunas of epochs or periods of time, but local topographical faunas. After the Corniferous period, corals, crinoids, and trilobites still flourished somewhere, as before, but they are absent from the Central Interior until the Carboniferous age[53] opens."
Here we are certainly getting a refreshing breath of common-sense geology; but what would become of current theories if we enlarge a little on this idea?
What if the gigantic dinosaurs of the Cretaceous or the equally marvellous mammals of the "early" Tertiaries of the Western States, described by Marsh and Cope, and the Pleistocene mammals of other parts of America and of Europe and Northern Siberia, "are not strictly faunas of epochs or periods of time, but local topographical faunas?" What if the world-wide limestones of the Cambrian and Silurian, and the no less enormous or widespread nummulitic limestones of the Eocene, extending from the Alps to Eastern Asia, and constituting mountains ten, fifteen, or twenty thousand feet high—what if these are possibly contemporaneous with one another? Supposing the coal-measures of Nova Scotia and Pennsylvania, and the Cretaceous and Tertiary lignites of Vancouver Island, Alberta, and the Western States are not strictly floras of epochs or periods of time, but local topographical floras?[54]
But it must be confessed that the logical extension of this broad view of the fossils, and the projection of our modern zoological provinces and zones back into the fossil world would mean the death-blow to the life succession theory, and might have a very disturbing effect upon certain theories about human origins and other genetic relationships which have grown quite popular since the middle of the last century.