32 PREFACE. 



to the other. In many cases I have been able to confirmi old 

 records by the examination of the original material, as well as 

 add new collections not studied before. 



In the method of sequence the lowest and most generalized 

 groups are treated first, the more specialized -following. The 

 system of arrangement is largely that of Miss Mary J. Rathbun 

 in the Crustacea of New England. In framing the higher groups 

 as orders, suborders, families, tribes, genera, etc., all avail- 

 able information, from whatever source pertinent, has been 

 utilized, and is, therefore, the work of various writers. This 

 may be explained by the fact that in the Crustacea many writers 

 have confined themselves to a single or but a few groups, a prac- 

 tice often followed by entomologists and others. Thus great 

 differences in terminology as applied to really the same organs 

 become evident. I have not attempted to eliminate this feature, 

 but have tried to use such characteristic appellations as are in 

 use for each group of animals. 



It may also be well to note the various more important general 

 works briefly which have been utilized in the present groupings. 

 The Phyllopoda are treated in the exhaustive monograph by 

 Dr. Packard in 1883. The Ostracoda will be found in the ex- 

 haustive account by Messrs. C. L. Herrick and C. H. Turner in 

 1895, though several important papers on special groups have ap- 

 peared since. The parasitic Copepoda have recently been studied 

 by Dr. C. B. Wilson, the fresh-water forms by Herrick and 

 Forbes, and the free-swimming forms have been studied from 

 the Gulf Stream by Professor W. M. Wheeler. The Cirripedia 

 have been studied as early as 1851 by the masterly hand of 

 Charles Darwin, and recently the stalked forms have been treated 

 by Dr. Henry A. Pilsbry. The Amphipoda, in the discussion of 

 the Wood's Hole region, have been studied by Dr. S. J. Holmes. 

 The Isopoda have been monographed in the exhaustive and well 

 illustrated work of Miss Harriet Richardson. The Decapocla 

 have been studied and outlined in the article under the Synopses 

 of North American Invertebrates in 1899 and 1903, by Miss 

 Rathbun. It may also be stated that the Aimphipoda and 

 Isopoda, besides the Macrura, are included in similar fashion. 



