CONTEMPORARIES AND SUCCESSORS OP EOZOON. 161 



mens are from the older part of the Lower Silurian 

 series ; but unfortunately their minute structures are 

 not well preserved. 



In the Silurian and Devonian ages, these Stromato- 

 porse evidently carried out the same function as the 

 Eozoon in the Laurentian. Winchell tells us that in 

 Michigan and Ohio single specimens can be found 

 ^«veral feet in diameter, and that they constitute the 

 ^ftass of considerable beds of limestone. I have myself 

 ^^ften in Canada specimens a foot in diameter, with a 

 great number of laminge. Lindberg"^ has given a most 

 vivid account of their occurrence in the Isle of Goth- 

 land. He says that they form beds of large irregular 

 discs and balls, attaining a thickness of five Swedish 

 feet, and traceable for miles along the coast, and the 

 individual balls are sometimes a yard in diameter. In 

 some of them the structure is beautifully preserved. 

 In others, or in parts of them, it is reduced to a mass 

 of crystalline limestone. This species is of the Coeno- 

 stroma type, and is regarded by Lindberg as a coral, 

 though he admits its low type and resemblance to 

 Protozoa. Its continuous calcareous skeleton he 

 rightly regards as fatal to its claim to be a true 

 sponge. Such a fossil, differing as it does in minute 

 points of structure from Eozoon, is nevertheless proba- 

 bly allied to it in no very distant way, and a successor 

 to its Hmestone-making function. Those which most 

 nearly approach to Foraminifera are those with thick 

 and solid calcareous laminae, and with a radiating canal 



* Transactions of Swedish Academy, 1870. 



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