SUGGESTIONS CONCERNING NOMENCLATURE 393 



rora sandstone. And would it not have been better to refer to the 

 "Valley limestones^^ as undifferentiated Cambrian and Ordovician forma- 

 tions, instead of by the unclassifiable and hereafter quite useless name 

 "Shenandoah limestone" ? Or, to cite another case in which several dis- 

 tinct lithological units of very different ages, and thought to be too thin 

 to be separately delineated, were arbitrarily associated under the name 

 ''Tanola formation," would it not have been better to speak of this strip 

 of the map as covering undifferentiated Silurian and Devonian forma- 

 tions? Or, better still, if time had been taken to determine and define 

 the several stratigraphic units, as has since been done by Foerste,^^ they 

 might have been properly named and described in the text, though re- 

 maining wholly or partly undifferentiated on the map? Doubtless the 

 science of stratigraphy would benefit greatly if the formational units 

 were determined by the criteria and principles of the science rather than 

 by cartographic limitations and the time available for field studies. 



Eegarding the use of terms in two distinct senses, as, for instance, 

 Trenton limestone, meaning a formational unit of definite lithologic 

 characteristics and limited geographic extent, and Trentonian, referring 

 to a much broader time interval than that represented in the Trenton 

 limestone proper, I am unalterably opposed to it. Happily, the practice 

 is being rather generally discouraged, so that we may confidently look 

 forward to its entire and early abrogation. The use of the suffix an or 

 ian, which is commonly used to distinguish the term when employed in 

 a time sense, should never imply either more or less than a time space 

 corresponding in duration to that required to lay down the rocks known 

 by the simpler form of the term. Any departure from this rule leads 

 to confusion. As a rule, it seems to me we might get along very well 

 without using the suffix at all, except as applied to terms of the rank of 

 series or epochs. It may be more euphonious to say Trentonian time or 

 Trentonian age than Trenton time or Trenton age, but it is neither more 

 exact nor more easily understood. 



Finally there are occasioii? when in writing a term some obvious dis- 

 tinction between the two seii.?es in which it may be applied would be ad- 

 vantageous. Such occasions, however, need arise only when dealing with 

 names of formations used also in the time scale. It has been sug- 

 gested — and the plan seems a good one — to italicize the word when it 

 refers to the age and not to the lithologic unit itself. Other contingen- 

 cies suggest a similar mode of discrimination. Thus we may wish to 

 speak of some local lithological phase or part of a stage or series, as, for 



A. F. Foerste: Kentucky Geol. Survey, Bull. No. 7, 1006. 

 XXVII— -Bull. Geol. Soc. Am., Vol. 22, 1910 



