Stromatoporoids and of Eozooii. 'iOD 



In the presence of examples of Eozoon canadense with all 

 tlie details of tlieii- structure so perfectly preserved it is 

 amazini^- to think that they lived at a time so distant that 

 even the Cambrian epoch with its highly organized fauna 

 does not seem very remote. 



Note 14. — In each colony of Eozoon the horizontal rouleaux 

 radiate outwards from a dense vertical central sheaf composed 

 ot" strings of small Nutnmulitid shells without secondary 

 .•■keleton or witii only very little. 



At a time when I was deluded by theories of pressure and 

 by serpentine {(/nes fatui, I had thought that this dense 

 Central conical column or sheaf, seen in vertical sections 

 through the centre, was produced by a crush ing-in force. 

 The resemblance between Eozoon and, say, Stromatopora 

 concetilrica is now seen to be very close. Each may be 

 compared to a huge hemispherical mushroom with a very 

 small stem. In Eozoon the main body is composed of small 

 disks limited in size owing to secondary deposit. In Stroma- 

 topora the usually larger coils or disks are not thus limited. 

 Again, in its plume-like upwaid and outward growth the 

 Dawn Animal may be compared to a fountain. 



EXPLANATION OF THE PLATES. 



Plate XI. 



Fit/. ]. Stromatopora /liips'JiiijJhvg. Devonian, Teipnmoutli (P. 6328.) 

 Polished slab. Tai gential ^iew, i-howing- spiv.il systems. 

 Niit. size. 



Fit/, 2. Ilcematostroma episcopn/e, Nieh. (P. 5690 ) Polished slab. 

 Tauavntial view, showiug spiral systems and central chambers. 

 Nat. size. 



Fif/. 3. Actiiiostruina hebbornense, Nicli. Mid-Devonian, TeigninDiith. 

 A spiral system. X 6. 



Fif/. 4. Lahechici ct))ifL'rtUf Lonsdale. Very young- specime >, showing- 

 thin disk with coils. X '2. 



Plate XII. • 



Fig. 5. Fozoo7i canade?! se, Dawson. Vertical section, showing- alternating; 

 light layei"s of calcite (supplementary skeleton) and dark 

 layers (which contain piles of Nummulitid shells). Nat. size. 



Fi(/. 6. Eozoon canadense. I^ayers of coiled Nummulitid shells. The 

 calcareous supplementary skeleton has been dissolved by acid. 

 The shells lie in rouleaux in the green areas (olivine and 

 serpentine) boui ded \)y the supplementary skeleton. X -5. 



Fi(j. 7. Eozoon canadense. A single apparently broken-otl' Nummulitid 

 shell, showing- funicular umbilicus. X 190. 



