104 THE CANADIAN NATURALIST. [April 



These reasons are, I think, sufficient to justify me in regarding 

 these remarkable structures as truly organic, and in searching for 

 their nearest allies among the Foraminifera. 



Supposing then that the spaces between the calcareous laminae, 

 as well as the canals and tubuli traversing their substance, were 

 once filled with the sarcode body of a Rhizopod, comparisons with 

 modern forms at once suggest themselves. 



From the polished specimens in the Museum of the Canadian 

 Geological Survey, it appears certain that these bodies were sessile, 

 with a broad base, and grew by the addition of successive layers 

 of chambers separated by calcareous laminae, but communicating 

 with each other by canals or septal orifices sparsely and irregularly 

 distributed. Small specimens have thus much the aspect of the 

 modern genera Carpenter la and Polytrema. Like the first of 

 these genera, there would also seem to have been a tendency to 

 leave in the midst of the structure a large central canal, or deep 

 funnel-shaped or cylindrical opening, for communication with the 

 sea-water. Where the laminae coalesce, and the structure becomes 

 more vesicular, it assumes the ' acervuline' character seen in such 

 modern forms as Nuhecnhrria. 



Still the magnitude of these fossils is enormous when compared 

 with the species of the genera above named ; and from the speci- 

 mens in the larger slabs from Grenville, in the Museum of the 

 Canadian Survey, it would seem that these organisms grew in 

 groups, which ultimately coalesced, and formed large masses pene- 

 trated by deep irregular canals ; and that they continued to grow 

 at the surface, while the lower parts became dead and were filled 

 up with infiltrated matter or sediment. In short, we have to 

 imagine an organism having the habit of growth of Carpenteria, 

 but attaining to an enormous size, and by the aggregation of indi- 

 viduals assuming the aspect of a coral reef. 



The complicated systems of tubuli in the Laurentian fossil 

 indicate, however, a more complex structure than that ol any of 

 the forms mentioned above. I have carefully compared these with 

 the similar structures in the ' supplementary skeleton' (or the 

 shell-substance that carries the vascular system) of Ualcarina and 

 other forms,* and can detect no difference except in the somewhat 



* I desi'*e to express my obligations to the invaluable memoirs of Dr. 

 Carpenter on the Foraminifera, in the Transactions of the Royal 

 Society, and in the publications of the Ray Society ; without which 



