4 PREFACE. 



lu the preparation of the second edition, it was " found necessary 

 to entire!}^ recast the account of the Fishes, in order to include 

 the resuUs of recent investigations in that department. Tlie 

 author has availed himself of this opportunity to substitute for 

 the artificial keys in the previous edition, a series of generic 

 diagnoses, wliich, while serving the purpose of a ' key,' also serve 

 to express the true relations of the species." The author regrets 

 that this change can not in the present edition be extended to all 

 the groups included in the work, as well as to the Fishes. 



D. S. J. 



NOTE TO FOURTH EDITION. 



This edition is from the same stereotype plates as the second 

 (1878) and third (1880). In the groups other than the Fishes, 

 the nomenclature has been changed in several places. It is now 

 brought fully up to date, so far as it is possible to do so without 

 alteration in the arrangement of the genera or insertion of addi- 

 tional matter. The account of the Fishes remains exactly as in 

 the third edition. Changes in this group have been deemed less 

 necessary, as those especially interested will find an account of 

 the recent additions and modifications in Jordan & Gilbert's 

 Synopsis of the Fishes of North America, published by the 

 Smithsonian Institution in 1883. D. S. J. 



Bloomington, Ind , April, 1884. 



