. VI. NOMENCLATURE. 199 



factions, (fetrificata), a term confessedly inappli- 

 cable to a large part of the subjects generally 

 ranked under itf. Larvata bas been substituted 

 in the room of petrifactions ; but this is., also, an 

 appellation vhich, in numerous instances, by no 

 means accords with the bodies it is meant to indi- 



t Hence, some authors have excluded from the class, as not 

 properly according with the term petrifactions, all the unniine- 

 ralized extraneous fossils ; but this is an unnecessary accommoda- 

 tion to a mere name, and deprives the study of a considerable 

 portion of interest, as the remains of plants and animals, occurring 

 in an unchanged state, afford some of the most curious objects of 

 investigation, in the whole circle of natural science. Nor, indeed, 

 as far as respects their systematic arrangement, is there any just 

 principle by which petrifactions, properly so called, can be sepa- 

 rated from organic remains in the state of conservata (. II. 2. 

 p. 4.) It will be readily admitted, that the distinctions, under 

 which any tribe or class of natural bodies is distributed into ge- 

 nera or less divisions, ought to be founded on those characteristics 

 by which such tribe or class is primarily distinguished from others. 

 It is chiefly, perhaps, in the application of this principle, that the 

 arrangements of Linnaeus so greatly excel the systems of preced- 

 ing naturalists In his distribution of plants and animal, for in- 

 stance, the characteristic notes of the genera and subdivisions are 

 constantly taken from the figure, number, proportion, and situa- 

 tion of essential parts; the principle on which they are first 

 separated into classes and orders In the systems left us by Ray 

 and others, in almost every division, some new principle is assumed 

 for the establishment of a diagnostic ; and habitation and man- 

 ners frequently give character to the last members of an arrange- 

 ment, begun according to figure and internal structure. In 



