WHAT MAY BE LEARNED FROM EOZOON 143 



could obliterate the minutest points of structure ; and that 

 such fusion has not occurred, the preservation in the Laurentian 

 rocks of the most delicate lamination of the beds shows con- 

 clusively ; while, as already stated, it can be shown that the 

 alteration which has occurred might have taken place at a 

 temperature far short of that necessary to fuse limestone. 

 Thus has it happened that these most ancient fossils have 

 been handed down to our time in a state of preservation com- 

 parable, as Dr. Carpenter states, to that of the best preserved 

 fossil Foraminifera from the more recent formations that have 

 come under his observation in the course of all his long ex- 

 perience. 



Let us now look more minutely at the nature of the typical 

 specimens of Eozoon as originally observed and described, and 

 then turn to those preserved in other ways, or more or less de- 

 stroyed or defaced. Taking a polished specimen from Petite 

 Nation, we find the shell represented by white limestone, and 

 the chambers by light green serpentine. By acting on the 

 surface with a dilute acid we etch out the calcareous part, 

 leaving a cast in serpentine of the cavities originally occupied 

 by the soft animal substance, and when this is done in polished 

 slices, these may be made to print their own characters on 

 paper, as has actually been done in the plate prefixed, which 

 is an electrotype from an etched specimen, and shows both 

 the laminated and acervuline parts of the fossil. If the pro- 

 cess of decalcification has been carefully executed, we find in 

 the excavated spaces delicate ramifying processes of opaque 

 serpentine or transparent dolomite, which were originally im- 

 bedded in the calcareous substance, and which are often of 

 extreme fineness and complexity. 1 (Figs. 18, 19.) These are 

 casts of the canals which traversed the shell when still inhabited 

 by the animal, and have subsequently been filled with mineral 



1 Very fine specimens can be produced by polishing thin slices, and then 

 etching them slightly with a very weak acid. (Plate prefixed.) 



