PREFACE. IX 



scale, and enlarged his system by the additional genera 

 of other Testaceologists. The arrangement of Lamarck 

 is strictly preserved in the orders and families, and the 

 new genera have been placed as nearly as possible in 

 the situations which they would naturally occupy in 

 his system. 



The Linnsean arrangement was long followed as the 

 best, and is still adopted by many naturalists. Since 

 his time, however, the immense accumulation of new 

 species, with characters which are likewise new, ren- 

 ders the task of classifying them according to his 

 method, extremely difficult, if not impracticable. We 

 have, nevertheless, given his arrangement, as well as 

 that of the modern school, leaving it to the decision of 

 the student which he will adopt. 



