WHAT IS EOZOON ? 79 



tlie Lower Silurian. Professor Hall lias described specimens 

 of Eeceptaculites twelve inches in diameter ; and the fossils 

 from the Potsdam formation of Labrador, referred by Mr. 

 Billings to the genus Archeeocyathus, are examples of Protozoa 

 with calcareous skeletons scarcely inferior in their massive 

 style of growth to the forms now under consideration. 



"These reasons are, I think, sufficient to justify me in re- 

 garding these remarkable structures as truly organic, and 

 in searching for their nearest allies among the Foramini- 

 fera. 



" Supposing then that the spaces between the calcareous 

 lamina, as well as the canals and tubuli traversing their sub- 

 stance, 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 by 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 

 Carpenteria 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 lamiuEe coalesce, and the structure 

 becomes more vesicular, it assumes the ' acervuUne ' charac- 

 ter seen in such modern forms as Nubecularia. 



" Still the magnitude of these fossils is enormous when 

 compared with the species of the genera above named; and 

 from the specimens 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 penetrated 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 organ- 

 ism having the habit of growth of Carpenteria, but attaining 



