Dawson — Addendum to Paper on Eozoon. 
129 
XXII. — Addendum to Papee on Eozoon. By J. W. Dawson, LL. D., 
E. R. S., Principal of the M'Gill College, Montreal. 
[Read April 10, 1871.] 
In pursuing the researches referred to in the Paper read before the 
Academy, Pebruary 13th, 1878,"^' two points have occurred which are, 
in my opinion, so instructive that I desire to add a short notice of 
them. 
The first relates to a limestone, probably of Upper Silurian age, 
collected by Mr. Robb, of the Geological Survey, and kindly placed in 
my hands by Mr. Selwyn. The locality is Pole-hill, IN'ew Brunswick. 
This limestone is composed almost wholly of organic fragments, 
cemented by crystalline carbonate of lime, and traversed by slender 
veins of the same mineral. Among the fragments may be recognised 
under the microscope portions of Trilobites, and of brachiopod and 
gasteropod shells, and numerous joints and plates of Crinoids. The 
latter are remarkable for the manner in which their reticulated 
structure, which is precisely similar to that of modern Crinoids, has 
been injected with a siliceous substance, which is seen distinctly in 
slices, and still more plainly in decalcified specimens. This filling 
is precisely similar in appearance to the serpentine filling the canals 
of Eoizoon, the only apparent difference being that in the forms of the 
cells and tubes of the Crinoids, as compared with those of the Lauren- 
tian fossil, the same silicious substance also occupies the cavities of 
some of the small shells, and occurs in mere amorphous pieces, 
apparently filling interstices. Erom its mode of occurrence, I have 
not the slightest doubt that it occupied the cavities of the crinoidal 
fragments while still recent, and before they had been cemented 
together by the calcareous paste. This siliceous filling is therefore 
similar, on the one hand, to that effected by the ancient serpentine of 
the Laurentian, and on the other to that which results from the 
deposition of modern glauconite. The analysis of Dr. Hunt, which I 
give below, fully confirms these analogies. 
I may add that I have examined under the microscope portions of 
the substance prepared by Dr. Hunt for analysis, and find it to retain 
its form, showing that it is the actual filling of the cavities. I have 
also examined the small amount of insoluble silica remaining after his 
treatment with acid and alkaline solvents, and find it to consist of 
angular and rounded grains of quartzose sand. 
The following are Dr. Hunt's notes : — 
''The fossiliferous limestone from Pole-hill, Kew Brunswick, pro- 
bably of Upper Silurian age, is light gray and coarsely granular. 
When treated with dilute hydrochloric acid, it leaves a residue of 5-9 per 
cent., and the solution gives 1"8 per cent, of alumina and oxide of iron. 
* *' Proceedings K. I. A.," New Series, vol. i., p. 117, 
R. I. A. PROC VOL. I., SER. II., SCIENCE. S 
