260 PEOCEEBINGS OF THE GEOLOGICAL SOCIETY. [May 8, 



in carbonate of lime. The specimens which, enabled me to make 

 that statement were obtained at Madoc, near Tudor, this region being 

 one in which the Lanrentian rocks of Canada appear to be less 

 highly metamorphosed than is usual. The specimens from Madoc, 

 however, were mere fragments, imbedded in the limestone, and in- 

 capable of showing the general form. I may explain, in reference 

 to this, that long practice in the examination of these limestones 

 has enabled me to detect the smallest fragments of Eozoon when 

 present, and that in this way I had ascertained the existence of this 

 fossil in one of the limestones of Madoc before the discovery of the 

 fine specimen now under consideration. 



I am disposed to regard the present specimen as a young indi- 

 vidual, broken from its attachment and imbedded in a sandy calca- 

 reous mud. Its discovery affords the hope that the comparatively 

 unaltered sediments in which it has been preserved, and which also 

 contain the worm-burrows described by me in the ^ Quarterly Journal 

 of the Geological Society' for November*, wiU hereafter still more 

 largely illustrate the Laurentian fauna. 



II. Specimens eeom Long Lake and Wentwohth. 



Specimens from Long Lake, in the collection of the Geological 

 Survey of Canada, exhibit white crystalline limestone with light-green 

 compact or septariiformf serpentiue, and much resemble some of the 

 serpentine-limestones of Grenville. Under the microscope the cal- 

 careous matter presents a delicate areolated appearance, without 

 lamination ; but it is not an example of acervuline Eozoon, but rather 

 of fragments of such a structure, confusedly aggregated together, and 

 having the interstices and cell-cavities filled with serpentine. I have 

 not found in any of these fragments a canal- system similar to that 

 of Eozoon Oanadense, though there are casts of large stolons, and, 

 under a high power, the calcareous matter shows in many places 

 the peculiar granular or cellular appearance which is one of the 

 characters of the supplemental skeleton of that species. In a few 

 places a tubulated cell- wall is preserved, with structure similar to 

 that of Eozoon Canadense. 



Specimens of Laurentian limestone from Wentworth, in the collec- 

 tion of the Geological Survey, exhibit many rounded siliceous bodies, 

 some of which are apparently grains of sand, or small pebbles ; but 

 others, especially when freed from the calcareous matter by a dilute 

 acid, appear as rounded bodies, with rough surfaces, either separate 

 or aggregated in lines or groups, and having minute vermicular pro- 

 cesses projecting from their surfaces (PL XII. fig. 3). At first sight 

 these suggest the idea of spicules ; but I think it on the whole more 

 likely that they are casts of cavities and tubes belonging to some cal- 

 careous Foraminiferal organism which has disappeared. Similar 

 bodies, found in the limestone of Bavaria, have been described by 



-"- Vol. xxii. p. 608. 



t I use the term " septariiform " to denote the curved appearance so often 

 presented by the Laurentian serpentine. 



