ence would affect bat one or two unimportant names among those in 

 the index, and would seem to be a necessary concession to a simple 

 matter of fact. 



The absolute synonymes resulting from the foundation of different 

 genera on the same species, and some which are generally admitted by 

 the majority of authors, have been indicated whenever known. In 

 some cases, the compiler has exercised his own judgment in inserting a 

 reference to synonymy. In every case, however, the student is requested 

 to refer to the citations of the index, upon which the compiler's indica- 

 tions of synonymy are based, and from them to form his own conclusions. 



It has been attempted to give in full the locuSj date, and reference to 

 figures (if any) appertaining to each original generic or other descrip- 

 tion ; with a reference to the original description of the typical species, 

 when this is not coincident with the generic or sectional diagnosis, to 

 indicate whether a diagnosis authenticated the introduction of a new 

 name or not (silence on this point in the citation indicating that a proper 

 diagnosis was made) ; to name and give citations for the type, if any 

 was selected, or to state the first species if no type was named, and the 

 types which have been adopted by subsequent students of the genus; 

 and to give a reference to the best figure of the typical species known 

 to the compiler. 



This has been done whenever practicable, and a reference to the 

 geological horizon of the type-species of a genus, with any notes which 

 might tend to elucidate its standing, have frequently been added. 



ISTerjly all the works referred to have actually been consulted. The 

 only important exceptions are those of Fischer de Waldheim, Konig and 

 one of Pander's minor papers. For an opportunity of consulting Pan- 

 der's Beitrage I am indebted to the kindness of Prof. Alexander Agassiz, 

 director of the Museum of Comparative Zoology at Cambridge. 



When a publication was inaccessible, the fact is stated in the citation, 

 T'^hich has then been derived from the works of Davidson, Bronn, Herr- 

 mannsen, and other standard authorities. To the first-named gentleman 

 and Prof. E. P. Whitfield, of Albany, I am under great obligations for 

 numerous favors received during the preparation of this index, for the 

 views expressed in which, however, I hold myself solely responsible. 



The classification of generic names which follows the index is for the 

 purpose of assisting the student to find at one reference all the binomial 

 names which appear to belong to any one family. Some pre-Linnaean 



