198 . VI. PRINCIPLES OF 



noticed under the specimens of accidental forms, 

 or of the constituent substances, accordingly as the 

 variations of the mode have occurred in one or 

 other. 



Specimens of accidental forms are always to he 

 carefully enumerated If the accidental forms in 

 a reliquium be not well distinguished, they are 

 liable to be mistaken for distinct, genuine species 

 or varieties. 



Specimens of the mineral substances of the rcli- 

 quimn (. III. 181.) should also be enumerated. 

 Such detail will contain information necessary for 

 the Geologist,, though not essential to the discrimi- 

 nation of the species. 



. VI. 

 PRINCIPLES OF NOMENCLATURE. 



The appellations, distinguishing extraneous fossils 

 in a systematical arrangement, are generally formed 

 or selected with a reference to the names by which 

 the recent subjects are designated. 



Names, in a systematical arrangement., are those 

 of the Class,, Orders,, Families, and Species. 

 Name of the Class. 



Extraneous fossils, considered as a class, have 

 frequently been distinguished by the title of petri- 



