FORAMINIFERA. 125 



some cases the chambers are simply filled with crystalline 

 carbonate of lime. When the originally porous fossil has 

 been permeated by a silicate, it is possible to dissolve away 

 the whole of the calcareous skeleton by means of acids, 

 leaving an accurate and beautiful cast of the chambers and 

 the tubes connected with them in the insoluble silicate. 



From the point of view that Eozoon is truly Foraminiferal, 

 it must be regarded as a gigantic member of the Nummu- 

 linida, which must have grown in reef-like masses. It also 

 has decided affinities to the Eotaline genera Polytrema and 

 Calcarina, resembling the former in its irregular mode of 

 growth, while it approaches the latter in intimate structure. 

 The test in Eozoon is distinctly of a Nummuline type, as 

 shown by its possessing a minutely porous or tubular " proper 

 wall " to the sarcode-chambers, while there is also a largely 

 developed " intermediate " or " supplemental " skeleton, pene- 

 trated by a " canal-system ; " but it differs from all the known 

 Nummulinida in its indefinite and often " acervuline " mode 

 of increase. The minute structure of the test will be readily 

 understood by comparing figs. 26 and 27 with fig. 17 c, the 

 latter representing a much-enlarged view of part of the test 

 of Calcarina. On the other hand, Professors King and 

 Eowney, Mr Carter, and others, maintain that Eozoon is 

 inorganic, and that its so - called " proper wall " is really 

 nothing more than fibrous serpentine. 



Eozoon Canadense occurs in the crystalline metamorphic 

 limestones of the Lower Laurentian in Canada, and it has 

 also been detected in the same country in similar limestones 

 believed to be of the age of the Upper Laurentian or Hu- 

 ronian. An allied form (species ?) has been found in rocks 

 supposed to be Laurentian in Newfoundland ; Dr Giimbel 

 has described a third form from crystalline limestone belong- 

 ing to the " Hercynian gneiss formation " (Lower Cambrian 

 or Huronian ?) of Bavaria ; while similar structures are stated 

 to occur in the serpentinous marbles of Connemara in Ireland 

 (which are thought to be of Lower Silurian age). 



Lastly, Dr Dawson has given the name of Archceosphcerince 

 to small spherical masses of serpentine, sometimes single, 

 sometimes united together in small numbers, which he finds 



