360 PALEONTOLOGY 



in the course of an ordinary sentence it should be printed 

 in different type from the rest of the sentence (normally, 

 in a sentence of roman type it would be in italics). A 

 few examples will show the importance of adhering to 

 these rules. If in a geological work we come across an 

 allusion to " the Planorbis beds," we should know that 

 it referred to beds in which there were abundant gastro- 

 pods belonging to the freshwater genus Planorbis; but 

 when we read of "the planorbis-beds," we understand 

 marine beds characterized by the ammonite Psiloceras 

 planorbis. The Productus-limestone is a well-known 

 Asiatic formation characterized by the brachiopod genus 

 Productus ; but an allusion to " the productus-limestone " 

 would set us puzzling our brains for the genus which 

 had a species with the trivial name producttis. As to the 

 third rule above, it is only necessary to hunt for the name 

 of a fossil in some work which has not followed that rule 

 to realize its importance. 



When several species of a genus are referred to in the 

 same paragraph, it is permissible to use the initial letter 

 only of the generic name, to save repetition. 



If no author had ever, by accident or otherwise, broken 

 the rules of nomenclature, the generic and trivial names 

 would suffice to define a species absolutely. It has been 

 found necessary, however, to avoid confusion, to write 

 after the name of a species the name of its author i.e., of 

 the palaeontologist who first applied that name to it ; and 

 it is often useful to add the date of his giving the name, 

 thus: Terebmtula intermedia J. Sowerby, 1812. 



There is no rule as to the type in which the author's 

 name should be printed, but it is not desirable that it 

 should be in the same type as either the specific name or 

 the rest of the sentence in which it occurs. 



The need for further rules arises from the facts that 

 authors writing at different times have from time to time 



