354 ON GEOLOGICAL NOMEKCLATUEE. 



The hierarchical terms which the Professor proposes and uses in 

 his table are these — 



1. — Era e.g., Tertiary or Caenozoic. 



2. — Period „ l^ummulite. 



3. — Epoch or System ,, Sub-apennine. 



4. — Age or stage, horizon ,, Astien 



These words before they are generally adopted in a quasi-technical 

 sense will of course be subjected to criticism ; and we may venture 

 to remark that there seems not quite enough difference in meaning 

 between the words of the first column, which express the chrono- 

 logical point of view. "We may suggest the word "^on'* as 

 perhaps likely to be useful. Our terminology will still be 

 defective because we have no words to express the former two 

 divisions from a petro graphical point of view. With respect to the 

 word ** system," we throughly approve of the place which is here 

 given to it. Its connection with the Silurian epoch through the 

 classical work of Murchison would compel us in England to 

 restrici it to divisions of this rank and value. Professor Eenevier 

 remarks that in giving the word this value he has had to dethrone 

 the ^^ etages^^ of D'Orbigny, and make them take the lower place. 

 Mr. K. Mayer also does the same. It would certainly be an im- 

 provement if geologists would follow our author's suggestion, and 

 agree upon a definite hierarchy of words. 



With respect to the nomenclature of the various sub-divisions and 

 groups, Professor Eenevier says that he has innovated as little as 

 possible by usually adopting terms hitherto in use : even the words 

 *' gatdt " and " culm" are used, though they are incapable of taking 

 the Erench adjective termination, and so agreeing with most of the 

 other designations. The words "Keuper," ''Ludlow," and 

 "Caradoc," as applied to show a certain age of rocks, will be 

 easily recognised in their Erench dress. Other examples of words 

 which Professor Eenevier has coined, though he deprecates their 

 being called innovations, are "Gryphitien" for Gryphcea arcuata 

 beds, " Opalinien " for Amm. opalinus beds. That he is no purist, 

 is shown by his spelling the word Ludlowien, which stands for the 



