684 REVIEWS 



the term Medinan which, as here used by Dr. Ulrich and Dr. Bassler, 

 includes most of the Oswegan of Clarke and Schuchert plus the Rich- 

 mond or uppermost Ordovician formation of most other authors. Those 

 who wish to use the term Medinan without including formations in both 

 the Silurian and Ordovician of most authors can use it as Dr. Swartz 

 does in the present volume and as proposed by Cumings in the Handbook 

 of Indiana Geology. The latter definition limits it to the beds between 

 the Clinton (Hall, Genesee River section) and the Queenston, thus con- 

 fining the name to the Silurian system as that term is used in Canada 

 and most of the United States. At least five different meanings have 

 been assigned to the term Medina or Medinan during the last ten years, 

 not including such combinations as "Upper Medinan Albion formation" 

 of the present volume. As nomenclature matters now stand, no other 

 term unless it is Clinton can be more highly recommended to a geologist 

 who, through lack of information or some other reason, finds it incon- 

 venient to use a name with a precise meaning for a lower Silurian horizon. 

 Stratigraphic palaeontology presents no more baffling problem than 

 the question of how to protect it from its friends. Until they are willing 

 to use a common nomenclature the subject will become steadily a less 

 exact science, if not a chaos, and fairly deserve the contempt of workers 

 in the more exact sciences. If the history of geology from the days of 

 Murchison and Sedgewick down to 1923 proves any one thing more 

 clearly than others, it is that specialists may nearly always be counted 

 on to completely disagree among themselves regarding the adjustment of 

 nomenclature questions which concern other geologists quite as much as 

 themselves. It seems therefore that the larger questions in geologic 

 nomenclature such as the Ordovician- Silurian boundary should not be 

 left indefinitely at the mercy of dialectic combat. In such cases the com- 

 mon sense of North American geologists should be enlisted in approving 

 one of the two contentions or a possible third proposal. This could be 

 secured by means of a committee representing all of the organizations or 

 institutions concerned with the promotion of geological science in North 

 America. While the decisions of such a committee would be binding 

 on no one they would certainly furnish responsible survey heads, college 

 professors, authors of textbooks and others who stand between the 

 specialists and the pubHc, a valuable index of general geologic opinion 

 concerning any disputed point in geological nomenclature, and have in 

 general a steadying influence on the fluctuations of geological 

 nomenclature. 



