68 J. W. DAWSON ON THE OCCURRENCE OF 



1. Limestone with crystals of dolomite and a few fragments of Eozoon. 



2. Fine-grained limestone with granules of serpentine — the latter filling the 



chamberlets of fragments of Eozoon and small globigerine Foraminifera. 



3. Limestone with dolomite and including a thin layer of serpentine as above. 



4. Limestone and dolomite with grains of serpentine and fragments of supple- 



mental skeleton of Eozoon. 



5. Crystallized dolomite, holding a few fragments of Eozoon in the state of 



calcite. 



6. Limestone with disseminated serpentine as above, chamberlets of Eozoon and 



fragments of its supplemental skeleton, also small groups of chamberlets, 

 perhaps globigerine Foraminifera. 



Ill other specimens a like thickness of rock presented a mass of 

 fragments of supplemental skeleton with the canals injected with 

 serpentine, and granules of the same filling the chambers. 



The chrysotile veins, which are sometimes an inch or more in 

 thickness, but branch off into the most minute fibres, are evidently 

 altogether subsequent in origin to the bedded limestone and ser- 

 pentine. They are undoubtedly of aqueous origin, and in their 

 mode of occurrence strongly resemble the veins of fibrous gypsum 

 penetrating the Lower Carboniferous marls of Nova Scotia. They 

 cross the bedding in all directions, and pass through the structure 

 of Eozoon, though sometimes running parallel to its lamina) for short 

 distances. They must have been introduced after the Eozoon was 

 mineralized, and have evidently no connexion with its structure. 



In the diagram (PI. X. fig. 2) I have attempted to represent this 

 relation ; and I have no hesitation in stating that the assertion that 

 these chrysotile veins are identical with or similar to the proper wall 

 of Eozoon either in structure or distribution, is wholly without foun- 

 dation, other than that which may arise from confounding dissimilar 

 structures accidentally associated with each other. 



Some slickensided joints lined with a lamellar and fibrous ser- 

 pentine traverse the beds, and, as the chrysotile veins sometimes 

 terminate in them, may be older than the latter. These also were 

 observed to cross the masses of Eozoon. 



Few disseminated minerals, other than those already mentioned, 

 were observed in the Eozoon limestone. A few detached crystals of 

 mica, pyroxene, and pyrite were found in the fragmental layers, and 

 also a few rounded particles of quartz, probably grains of sand. 



The perfect examples of Eozoon, at least those rendered evident 

 by mineralization with serpentine, are confined to certain bands of 

 limestone, and notably to one band — that originally opened by Mr. 

 Lowe. In this bed the fossil occurs in patches of various sizes, some 

 of them two feet or more in diameter, and bent or folded by the 

 contortions of the strata ; others are much smaller, down to a few 

 inches. On the weathered surfaces the specimens mineralized with 

 serpentine project, and exhibit their lamination in great perfection, 

 resembling very closely the silicified Stromatoporce of the Corniferous 

 Limestone. 



None of the specimens of Eozoon is of any great vertical thick- 

 ness. The lower laminae are generally the best developed and with 

 the thickest supplemental or intermediate skeleton. The upper 



