On the Structure of certain Organic Remains in the Laurentian Limestones of Canada

Abstract

A t the request of Sir William E. Logan, I have submitted to microscopic examination slices of certain peculiar laminated forms, consisting of alternate layers of carbonate of lime and serpentine, or of carbonate of lime and white pyroxene, found in the Laurentian Limestones of Canada, and regarded by Sir William as possibly fossils*. I have also examined slices of a number of limestones and serpentines from the Laurentian Series, not showing the external forms of these supposed fossils. The slices were prepared by the lapidary of the Survey, and were carefully examined under ordinary and polarized light, with objectives made by Ross and Smith & Beck, and also with good French objectives. The specimens first mentioned are masses, often several inches in diameter, presenting to the naked eye alternate laminæ of serpentine, or of pyroxene, and carbonate of lime. Their general aspect, as remarked by Sir W. E. Logan (Geology of Canada, 1863, p. 49), reminds the observer of that of the Silurian Corals of the genus Stromatopora , except that the laminæ diverge from and approach each other, and frequently anastomose or are connected by transverse septa. Under the microscope the resemblance to Stromatopora is seen to be in general form merely, and no trace appears of the radiating cells characteristic of that genus. The laminæ of serpentine and pyroxene present no organic structure, and the latter mineral is highly crystalline. The laminæ of carbonate of lime, on the contrary, retain distinct traces of structures which cannot be of a