166 THE DAWN OF LIFE. 



Phillip's genus Caunopora was formed to receive specimens 

 with concentric cellular layers traversed by " long vermiform 

 cylindrical canals ;" while Winchell's genus Coenostroma in- 

 cludes species with these vermiform canals arranged in a radiate 

 manner, diverging from little eminences in the concentric 

 laminae. The distinction between these last genera does not 

 seem to be very clear, and may depend on the state of preser- 

 vation of the specimens. A more important distinction 

 appears to exist between those that have a single vertical canal 

 from which the subordinate canals diverge, and those that have 

 groups of such canals. 



Some species of the Coenostroma group have very dense cal- 

 careous laminsB traversed by the canals ; but it does not seem 

 that any distinction has yet been made between the proper 

 wall and the intermediate skeleton ; and most observers have 

 been prevented from attending to such structures by the 

 prevailing idea that these fossils are either corals or sponges, 

 while the state of preservation of the more delicate tissues is 

 often very imperfect. 



B. Localities of Eozoon, or of Limestones supposed to 



CONTAIN IT. 



In Canada the principal localities of Eozoon Canadense are 

 at Grenville, Petite Nation, the Calumets Eapids, Burgess, 

 Tudor, and Madoc. At the two last places the fossil occurs in 

 beds which may be on a somewhat higher horizon than the 

 others. Mr. Vennor has recently found specimens which have 

 the general form of Eozoon, though the minute structure is not 

 preserved, at Dalhousie, in Lanark Co., Ontario. One speci- 

 men from this place is remarkable from having been mineral- 

 ized in part by a talcose mineral associated with serpentine. 



I have examined specimens from Chelmsford, in Massa- 

 chusetts, and from Amity and Warren County, New York, the 

 latter from the collection of Professor D. S. Martin, which 

 show the canals of Eozoon in a fair state of preservation, 

 though • the specimens are f ragmental, and do not show the 

 laminated structure. 



