1867.] 



and Affinities of Eozoon Canadense. 



507 



bedded in a calcareous matrix ; which I therefore feel justified in re- 

 garding as a finely tubulated Nummuline shell, of which the tubuli that 

 were originally occupied by pseudopodia have been permeated by sili- 

 ceous infiltration. 



So, again, while asserting that by no conceivable process could the 

 animal substance originally occupying these tubuli have been replaced 

 by siliceous minerals, they have entirely ignored the fact stated by me, 

 that this very replacement has taken place in recent specimens in my 

 possession, — a fact on the basis of which the reconstruction of the animal 

 of Eozoon proposed by Dr. Dawson and myself securely rests. 



The question may now, I believe, be regarded as conclusively settled by 

 the recent discovery, in a sedimentary limestone of the Lower Lauren- 

 tian formation at Tudor in Canada, of a specimen of Eozoon presenting . 

 characters that cannot, in the opinion of the most experienced Palaeon- 

 tologists and Mineralogists, be accounted for on any other hypothesis 

 than that of its organic origin. For in the first place, the occurrence 

 of a calcareous framework or skeleton in a matrix of sedimentary lime- 

 stone, which also fills up its interspaces, altogether excludes the hypothe- 

 sis that this framework might be the product of any kind of pseudo- 

 m Orphic arrangement produced by the separation of calcareous and 

 siliceous minerals from a solution containing both. And, secondly, this 

 specimen exhibits that which had not previously been distinctly seen in 

 any other, viz., a distinctly limited contour, formed by the curving 

 downwards and closiug-in of the septa, in a manner as perfect and 

 characteristic as the closing-in of the successive chambers of any poly- 

 thalamous shell. I believe that no Palaeontologist familiarwith Palseozoic 

 fossils would have hesitated to pronounce this specimen a Eossil Coral 

 allied to Stromatopora, if it had occurred in a Silurian Limestone. 



That this specimen, though differing greatly in appearance from the 

 ordinary serpentinous iJo^^ooi^, really represents that organism, is shown 

 not merely by the general arrangement of the calcareous lamellse, but by 

 their minute structure. This, it is true, is far less characteristically seen 

 in thin sections microscopically examined, than it is in the specimens 

 whose cavities have been filled up by Serpentine ; the texture of which 

 is often so marvellously little changed, as to have all the appearance of 

 recent shell-substance. But the alteration M-hich the slielly layers have 

 undergone in this specimen, is precisely paralleled by that which I have 

 been accustomed to find in the best-preserved specimens of other 

 organic structures contained in the more ancient Limestones. And 

 there are still distinctly-recognizable traces of the canal-system imper- 

 fectly injected with black substance, which correspond with those of 

 the ordinary Serpentinous Eozoon. 



Eor the imperfection of the specimen in this respect, however, full 

 compensation is made in the perfect preservation of the canal-system in 

 a small fragment of 'Eozoon long sipce observed by Di", Da^vson iu 



