108 THE CANADIAN NATURALIST. [April 



2. Intermixed with the fragments of Eozoon above referred to, 

 are other calcareous matters apparently fragmentary. They are 

 of various angular and rounded forms, and present several kinds 

 of structure. The most frequent of these is a strong lamination, 

 varying in direction according to the position of the fragments, 

 but corresponding, as far as can be ascertained, with the diagonal 

 of the rhombohedral cleavage. This structure, though crystalline, 

 is highly characteristic of crinoidal remains when preserved in 

 altered limestones. The more dense parts of Eozoon, destitute of 

 tubuli, also sometimes show this structure, though less distinctly. 



Other fragments are compact and structureless, or show only a 

 fine granular appearance; and these sometimes include grains, 

 patches, or fibres of graphite. In Silurian limestones, fragments 

 of corals and shells which have been partially infiltrated with 

 bituminous matter show a structure like this. On comparison with 

 altered organic limestones of the Silurian system, these appearances 

 would indicate that, in addition to the debris of Eozoon, other 

 calcareous structures, more like those of crinoids, corals, and 

 shells, have contributed to the formation of the Laurentian 

 limestones. 



3. In the serpentine* filling the chambers of a large specimen 

 of Eozoon from Burgess, there are numerous small pieces of 

 foreign matter; and the silicate itself is laminated, indicating 

 its sedimentary nature. Some of the included fragments appear 

 to be carbonaceous, others calcareous ; but no distinct organic 

 structure can be detected in them. There are however in the 

 serpentine many minute rounded siliceous grains of a bright green 

 color, resembling green-sand concretions ; and the manner in which 

 these are occasionally arranged in lines and groups suggests the 

 supposition that they may possibly be casts of the interior of 

 minute Foraminiferal shells. They may however be concretionary 

 in their origin. 



4. In some of the Laurentian limestones submitted to me by 

 Sir W. E. Logan, and in others which I collected some years ago 

 at Madoc, Canada West, there are fibres and granules of carbon- 

 aceous matter, which do not conform to the crystalline structure, 

 and present forms quite similar to those which in more modern 

 limestones result from the decomposition of algae. Though retain- 

 ing mere traces of organic structure, no doubt would be entertained 



[* This is the dark green mineral named loganite by Dr. Hunt.] 



