An eminent example is the Silurian limestone of Pole Hill, in New Brunswick, collected by the late Mr. Robb, of the Geological Survey, and referred to in the text. I cannot doubt that the silicate injecting Crinoids and other fossils in this limestone must have been introduced into these when still recent, and the same remark applies to the serpentine filling a coral at Lake Chebogamong, and fragments of corals at Melbourne, in Eastern Canada, and to the similar mineral filling fossils in a limestone from Llangwyllog, in Wales, and in that of Maxville, Ohio. Hunt regarded all these as coming essentially into the same category as regard to general composition and properties. His analysis of the minerals from Pole Hill and Llangwyllog is as follows:—
| Pole Hill. | Llangwyllog. | |||
| Silica | 38·93 | 35·32 | ||
| Alumina | 28·88 | 22·66 | ||
| Protoxyd of iron | 18·86 |
| 24·12 |
|
| Magnesia | 4·25 | 6·96 | ||
| Potash | 1·69 | 1·40 | ||
| Soda | ·48 | 0·67 | ||
| Water | 6·91 | 11·46 | ||
| Insoluble, quartz | ||||
| ——— | ——— | |||
| 100·00 | 99·89 |
These minerals approach in composition to the jollyte of Von Kobell, from which they differ in containing a portion of alkalies, and only one half as much water. In these respects they agree nearly with the silicate found by Robert Hoffman, at Raspenau, in Bohemia, where it occurs in thin layers alternating with picrosmine, and surrounding masses of Eozoon in the Laurentian limestones of that region;[51] the Eozoon itself being there injected with a hydrous silicate which may be described as intermediate between glauconite and chlorite in composition."
[51] Journ. fur Prakt. Chemie, Bd., 106 (1869), p. 356.
In the Welsh specimen the silicate is of a deep green colour, except where oxidized, and though only 3 per cent, of the whole, is sufficient to give it an olive colour and slight serpentinous lustre. In the Pole Hill material, the silicate amounts to 5 per cent, of the whole, and is of a greyish colour. For some further particulars, see my Paper on "Fossils Mineralized with Silicates" (Journal Geological Society, February, 1879).
C. Affinities of Eozoon, etc., with more Modern Forms.
Dr. Carpenter, who in admirable papers, which I need not quote here,[52] has illustrated in detail the structures of Eozoon, and shown its resemblance to modern forms, places Eozoon as a generalized type between the Nummuline and Rotaline groups of Foraminifera. It resembles the former in its fine and complicated tubulations, and some of the larger sessile forms of the latter in its habit of growth. More especially, this is near to that of the genera Carpenteria and Polytrema. In the former, more especially, there are a number of somewhat flattened calcareous cells with perforated walls, and built up in a conical form around a central pipe or funnel into which the apertures of the cells open. A specimen of Carpenteria, enlarged and having the walls of its cells thickened by a supplemental tubulated deposit like that of Calcarina, would approach very near to Eozoon.
[52] I may specially refer to the following:—
W. B. Carpenter on Eozoon Canadense. Intellectual Observer, No. xl., p. 300, 1865. Supplemental notes on the structure and affinities of Eozoon Canadense, Quart. Journ. Geol. Soc., Lond. Vol. xxii., pp. 219-228, 1866. Notes on the structures and affinities of Eozoon Canadense. Canad. Nat., new ser., vol. ii., pp. 111-119, wood-cut, 1865. A reprint from Quart. Journ. Geol. Soc., Lond., 1865. Further observations on the structure and affinities of Eozoon Canadense. In a letter to the President. Proc. Roy. Soc., Lond., vol, xxv., pp. 503-508, 1867. New observations on Eozoon Canadense. Ann. and Mag. Nat. Hist., sen 4, vol. xiii., pp. 456-470, one plate, 1874. Final note on Eozoon Canadense. Ann. and Mag. Nat. Hist., ser. 4, vol. xiv., pp. 371-372, 1874. Remarks on Mr. H. J. Carter's letter to Prof. King on the structure of the so-called Eozoon Canadense. Ann. and Mag. Nat. Hist., ser. 4, vol. xiii., pp. 277-284, with two engravings, 1874.