Dawson — On Eozoon Canadense. 
119 
which naturally create a prejudice against the idea of their being 
fossiliferous. That the authors themselves feel this is apparent from 
the slight manner in which they state the leading facts above given, 
and from their evident anxiety to restrict the question to the mode of 
occurrence of serpentine in limestone, and to ignore the specimens of 
Eozoon preserved under different mineral conditions. 
2. With reference to the general form of Eozoon and its structure 
on the large scale, I would call attention to two admissions of the 
authors of the Paper, which appear to me to be fatal to their case : — 
Eirst, they admit, at page 533 [Proceedings, vol.x.], their inability to 
explain satisfactorily" the alternating layers of carbonate of lime and 
other minerals in the typical specimens of Canadian Eozoon. They make 
a feeble attempt to establish an analogy between this and certain concen- 
tric concretionary layers ; but the cases are clearly not parallel, and the 
laminae of the Canadian Eozoon present connecting plates and columns 
not explicable on any concretionary hypothesis. If, however, they 
are unable to explain the lamellar structure alone, as it appeared to 
Logan in 1859, is it not rash to attempt to explain it away now, when 
certain minute internal structures, corresponding to what might have 
been expected on the hypothesis of its organic origin, are added to it ? 
If I al!irm that a certain mass is the trunk of a fossil tree, and another 
asserts that it is a concretion, but professes to be unable to account for 
its form and its rings of growth, surely his case becomes very weak 
after I have made a slice of it, and have shown that it retains the 
structure of wood. 
l^ext, they appear to admit that if specimens occur wholly com- 
posed of carbonate of lime their theory will fall to the ground. JSTow 
such specimens do exist. They treat the Tudor specimen with 
scepticism as probably strings of segregated calcite." Since the 
account of that specimen was published, additional fragments have been 
collected, so that new slices have been prepared. I have examined 
these with care, and am prepared to affirm that the chambers in these 
specimens are filled with a dark-coloured limestone not more crystal- 
line than is usual in the Silurian rocks, and that the chamber- walls 
are composed of carbonate of lime, with the canals filled with the 
same material, except where the limestone filling the chambers has 
-penetrated into parts of the larger ones. I should add that the strati- 
graphical researches of Mr. Yennor, of the Canadian Survey, have 
rendered it probable that the beds containing these fossils, though 
unconformably underlying the Lower Silurian, overlie the Lower 
Laurentian of the locality, and are, therefore, probably Upper Lauren- 
tian, or perhaps Huronian, so that the Tudor specimens may approach 
in age to Giimbel's Eozoon Bavaricum.^' 
* Dr. Hunt, in a recent communication to the " American Journal of Science" 
for July, 1870, p. 85, is disposed to regard them as belonging to a great series of 
strata not hitherto clearly recognised, lying at the base of the Primordial, but distinct 
from and newer than the Upper Laurentian and the Huronian. 
