Fig. 52.—Acervuline Variety of Eozoon, Côte St. Pierre.
(a) General form, half natural size. (b) Portion of cellular interior, magnified, showing the course of the tubuli.
Fig. 53.—Archæospherinæ from Côte St. Pierre.
(a) Specimens dissolved out by acid, the lower one showing interior septa. (b) Specimens seen in section.
In the Laurentian limestone of Wentworth, belonging apparently to the same band with that of St. Pierre, there are many small rounded pieces of limestone, evidently the debris of some older rock, broken up and rounded by attrition. In some of these fragments the structure of Eozoon may be plainly perceived. This shows that still older limestones composed of Eozoon were at that time undergoing waste, and carries our view of the existence of this fossil back to the very beginning of the Grenville series of the Laurentian.
With respect to organic fragments not showing the structure of Eozoon, I have not as yet been able to refer these to any definite origin. Some of them may be simply thick portions of the shell of Eozoon with their pores filled with calcite, so as to present a homogeneous appearance. Others have much the appearance of fragments of such Primordial forms as Archæocyathus, now usually regarded as corals or sponges; but after much careful search, I have thus far been unable to say more than I could say in 1865.
It is different, however, with the round cells infiltrated with serpentine and with the silicious grains included in the loganite. [Fig. 53] shows such bodies found mixed with fragmental Eozoon and in separate thin layers at Côte St. Pierre. In [Fig. 51], I have shown some of the singular grains found in the loganite occupying the chambers of Eozoon from Burgess, and in [Fig. 54] some remarkable forms of this kind found in the limestones of Long Lake and Wentworth. All these, I think, are essentially of the same nature, namely, chambers originally invested with a tubulated wall like Eozoon, and aggregated in groups, sometimes in a linear manner, sometimes spirally, like those Globigerinæ which constitute the mass of modern deep-sea dredgings and also of the chalk.
Fig. 54.—Archæospherinæ from Long Lake Limestone.
(Magnified.)
(a) Single cell, showing tubulated wall. (b, c) Portions of same more highly magnified, (d) Casts decalcified, and showing casts of tubules.
These bodies occur dispersed in the limestone, arranged in thin layers parallel to the bedding or sometimes in the large chamber-cavities of Eozoon. They are so variable in size and form that it is not unlikely they may be of different origins. The most probable of these may be thus stated. First, they may in some cases be the looser superficial parts of the surface of Eozoon broken up into little groups of cells. Secondly, they may be few-celled germs or buds given off from Eozoon. This would correspond with what Carpenter, and more recently Brady and Lester, have observed in the case of some of the larger of the modern Foraminifera. Thirdly, they may be smaller Foraminifera, structurally allied to Eozoon, but in habit of growth resembling those little globe-shaped forms which, as already stated, abound in chalk and in the modern ocean. The latter view I should regard as highly probable in the case of many of them; and I have proposed for them, in consequence, and as a convenient name, Archæospherinæ or ancient spherical animals. Carbonaceous matter is rare in the true Eozoon limestones, and, as already stated, I would refer the Laurentian graphite or plumbago mainly to plants.
Dr. Gümbel, the Director of the Geological Survey of Bavaria, is one of the most active and widely informed of European geologists, combining European knowledge with an extensive acquaintance with the larger and in some respects more typical areas of the older rocks in America, and stratigraphical geology with enthusiastic interest in the microscopic structures of fossils. He at once, and in a most able manner, took up the question of the application of the discoveries in Canada to the rocks of Bavaria. The spirit in which he did so may be inferred from the following extract:—