On Specimens of Eozoon Canadense. 205 
giving very complex appearances. I have in my collection 
a specimen of Stigmaria in which every vessel has been 
coated in the interior with successive linings of red and 
white calcite, and subsequently filled with calcite and pyrite, 
and in a Sternbergia from the coal formation the phrag- 
mata are silicified and encrusted with crystalline silica and 
pyrite, while the interstices are filled in with sulphate of 
barium. Such-complex and eccentric examples of fossili- 
zation are much more intricate than anything that occurs 
in the ordinary examples of Kozoon. 
Geologists should also be reminded that porous fossils, 
once infiltrated with siliceous minerals, are practically in- 
destructible. Nothing short of absolute fusion can wholly 
deface their structures, and these remain in many cases in 
the utmost perfection when the external forms have been 
wholly lost or inseparably united with the matrix. 
There is therefore nothing anomalous in the preservation 
of Eozoon, except its occurrence in rocks highly crystalline 
and of unusually great age; and but for these circumstances 
it is probable that no doubt would have been entertained on 
the subject. The question of the crystalline structure of 
rocks containing fossils deserves, however, some further 
consideration. 
That in limestones a crystalline condition is compatible 
with the preservation of fossils, and more especially with 
the preservation of their microscopic characters, is very 
well known. Many Palozoic limestones are of a highly 
crystalline character, and yet retain abundant evidence of 
their organic origin. For example, the Chazy and Trenton 
limestones of the vicinity of Montreal have a_ perfectly 
crystalline fracture, and present to the naked eye no trace 
of any form but cleavage planes of calcite, yet, when sliced 
and studied with the microscope, they are seen to consist of 
organic fragments having their most minute structures pre- 
served, but so completely enveloped and identified with the 
crystalline calcite which fills their pores and interstices that 
they cleave with it. It is to be observed also that in these 
limestones, instances occur in which organic fragments are 
