344 Scientific Proceedings, Royal Dublin Society. 



mineral marking, it appears to me that it ought not to be confined 

 to rocks of one formation, but should be common to all similar 

 rocks, no matter what their age may be ; similarly as we find 

 dendrites in rocks of nearly every age. 



As will appear from the first portion of this Paper, I am still 

 quite open to conviction ; but up to the present time the arguments 

 put forward in favour of Oldhamia being of organic origin seem to 

 me to be convincing. I therefore submit my views for the con- 

 sideration of those who are of an opposite opinion. 



