[Illustration: FIG. 26.—Section of _Loftusia Persica_. An Eocene Foraminifer. Magnified five diameters.—After Carpenter and Brady.] We thus have presented to us the remarkable fact that in the Palæozoic age we have no precise representative of _Eozoon_, but instead three divergent types, differing from it and from each other, all apparently specialised to particular uses, all temporary in their duration; while in later times nature seems to have returned nearer to the type of _Eozoon_, though on a smaller scale, and separating some characters conjoined in it. Some portion of this curious result may be due to our ignorance; and it would be interesting to know, what we may know some day, how this type of life was represented in the long interval between the Huronian and the Upper Cambrian, when perhaps there may have been forms that would at least enable us to connect _Eozoon_ and _Stromatopora_. Another link in the chain of being remains to be noticed here. In the Laurentian limestones we meet with numerous minute spherical bodies and groups of spheres with calcareous tubulated tests.[7] These may either be small Foraminiferæ, distinct from _Eozoon_, or may be germs or detached cells from its surface. Similar bodies are found in the lower part of the Siluro-Cambrian, in the Quebec group at Point Levis; and there they are filled with a species of glauconite constituting a sort of greensand rock. Still higher, in the Carboniferous, there are very numerous species of Foraminifera, presenting forms very similar to those in the modern seas, so that in the smaller shells of this group we seem to have evidence of a continuous series all the way from the Laurentian to the present time. The greater laminated forms co-exist with these up to the Eocene Tertiary. Throughout the whole of geological time—from the formation of the Laurentian limestones to that of the chalky ooze accumulating in the modern ocean—these humble creatures have been among the chief instruments in seizing on the calcareous matter of the waters and depositing it in the form of limestone. [Illustration: FIG. 27.—Foraminiferal Rock Builders, in the Cretaceous and Eocene. _a_, _Nummulites lævigata_—Eocene. _b_, The same, showing chambered interior. _c_, Milioline limestone, magnified—Eocene, Paris. _d_, Hard Chalk, section magnified—Cretaceous.]