1868.] DAWSON— EOZOON CANADENSE. 315 



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 dow under con- 

 sideration. 



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

 vidual, broken from its attachment and imbedded in a sandy 

 calcareous mud. Its discovery affords the hope that the com- 

 paratively 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,* 

 will hereafter still more largely illustrate the Laurentian fauna. 



II. SPECI3IENS FROM LONG LAKE AND WENTWORTH. 



Specimens from Long Lake, in the collection of the Geological 

 Survey of Canada, exhibit white crystalline limestone with light- 

 green compact or septariiformf serpentine, and much resemble 

 some of the serpentine-limestones of Grenville. Under the micro- 

 scope the calcareous matter presents a delicate areolated appear- 

 ance, 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 frag- 

 ments a canal-system similar to that of Eozoon Canadense, 

 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 supple- 

 mental 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 

 collection of the Geological Survey, exhibit many rounded silice- 

 ous 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 processes projecting from their surfaces 

 (PI. III. fig. 3). At first sight these suggest the idea of spicules ; 



* Vol. xxii. p. 608. 



t I use the term ' septariiforrn' to denote the curdled appearance so 

 often presented by the Laurentian serpentine. 



