XVI PREFACE. 



An attempt like this, to establish the elements 

 of a study, the objects of which form, as it were, 

 the common boundary between the organic and in- 

 organic kingdoms of nature, has unavoidably led to 

 details, that the already-informed naturalist may, per- 

 haps, think unnecessary, and sometimes even imperti- 

 nent I here particularly allude to the definitions of 

 the classes and orders of animals and plants, given at 

 page 77 86. the observations on mineral sub- 

 stances, p. J36 152. and the characters of such 

 families, in the systematic arrangement ofreliquia, 

 as are immediately founded on the known generic 

 distinctions of the recent subjects. To the mere 

 student, however, these explications are not unim- 

 portant : they will serve as first steps to the ac- 

 quirement of that knowledge, without which his 

 proficience in the study of extraneous fossils can be 

 but trifling. 



Technical language must of course alter, in 

 some degree, with the changes that progressively 

 take place in the science, to which it belongs. The 

 present treatise adds a very few terms to those 

 already used by naturalists : it is my wish, they may 

 not be found either useless or anomalous. 



It was my intention to have given, at the end 

 of the work, a list of authors who have written on 



