1867.] DAWSON-M-LAURENTIAN FOSSILS. 261 



Giimbel, who interprets them in the same way*. They may also 

 be compared with the siHceous bodies mentioned in a former paper 

 as occurring in the Loganite filling the chambers of specimens of 

 Eozoon from Burgess. 



III. Specimei^s feom Madoc. 



I have already referred to fragments of Eozoon occurring in the 

 limestone at Madoc, one of which, found several years ago, I did 

 not then venture to describe as a fossil. It projected from the sur- 

 face of the limestone, being composed of a yellowish dolomite, and 

 looking like a fragment of a thick sheU. When sliced, it presents 

 interiorly a crystalline dolomite, limited and separated from the 

 enclosing rock by a thin wall having a granular or porous structure 

 and excavated into rounded recesses in the manner of Eozoon. It 

 lies obliquely to the bedding, and evidently represents a hollow 

 flattened calcareous wall filled by infiltration. The limestone which 

 aiforded this form was near the beds holding the apparently worm- 

 burrows described in the Society's Journal for November, 1866. 



[A thin section of this body, carefully examined microscopically, 

 presents numerous and very characteristic examples of the canal- 

 system of Eozoon, exhibiting both the large widely branching 

 systems of canals and the smaller and more penicillate tufts 

 (PI. XII. figs. 4, 5) shown in the most perfect of the serpentinous 

 specimens — but with this difference, that the canals, being filled 

 with a material either identical with or very similar to that of the 

 substance in which they are excavated, are so transparent as only to 

 be brought into view b}^ careful management of the light. — W. B. C] 



lY. Objections to the Organic Nature of Eozoon. 



The discovery of the specimen from Tudor, above described, may 

 appear to render unnecessary any reference to the elaborate attempt 

 made by Profs. King and Eowney to explain the structures of 

 Eozoon by a comparison with the forms of fibrous and dendritic 

 minerals t, more especially as Dr. Carpenter has already shown 

 their inaccuracy in many important points. I think, however, that 

 it may serve a useful purpose shortly to point out the more essential 

 respects in which this comparison fails with regard to the Canadian 

 specimens — with the view of relieving the discussion from matters 

 irrelevant to it, and of fixing more exactly the limits of crystalline 

 and organic forms in the serpentine-limestones and similar rocks. 



The fundamental error of Messrs. King and Eowney arises from 

 defective observation— -in failing to distinguish, in the Canadian 

 limestones themselves, between organic and crystalline forms. This 

 is naturally followed by the identification of all these forms, whether 

 mineral or organic, with a variety of purely crystalline arrangements 

 occurring in other rocks, leading to their attaching the term 



* Proceedings of Eoyal Academy of Munich, 1866 ; Q. J. G. S. vol. xxii. pt. i. 

 p. 185 et seq. 



t Quart. Joiirn. Geol. Soe. vol. xxii. pt. ii. p. 23. 



