a 
s 
J. W. Dawson on fossils from the Laurentian of Canada. 371 
ing systems of canals and the smaller and more penicillate tufts 
hown in the most perfect of the serpentinous specime 
with this difference, that the canals, being filled with a material 
either identical with or very similar to that of the substance in 
ich they are excavated, are so transparent as only to be 
brought into view by careful management of the light.—w. B. c.] 
IV. Objections to the Organic Nature of Hozoon.—The discovery 
of the specimen from Tudor, above described, may appear to 
render unnecessary any reference to the elaborate attempt made 
by Profs. King and Rowney to explain the structures of Hozoon 
by a comparison with the forms of fibrous and dendritic miner- 
als,* more especially as Dr. Carpenter has already shown their 
maccuracy in many important points. I think, however, that it 
may serve a useful purpose shortly to point out the more essen- 
tial respects in which this comparison fails with regard to the 
Canadian specimens—with the view of relieving the discussion 
from matters irrelevant to it, and of fixing more exactly the 
limits of crystalline and organic forms in the serpentine lime- 
Stones and similar rocks. 
se 
forms. This is naturally followed by the identification of all 
these forms, whether mineral or organic, with a variety of baited 
mere lusus nature. : i 
A notable illustration of this is afforded by their regarding 
all the 
Structures indifferently and do not conform to the walls of the 
ut any microscopist who possesses specimens of 
containing these chrysotile veins may readil satisfy 
that, under a high power, they resolve themselves into 
it present the chrysotile, or bo any 
* Quart. Journ. Geol. Soc., vol. xxii, pt. ii, p. 23. 
