4 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



etc. As a rule, these could be satisfactorily cleared. Whenever 

 there was any doubt as to which was correct in part or as a whole, 

 both the author's citation and that of the editor's source were given, 

 the latter parenthetically. Several references made to Strauss have 

 been referred to Straus-Durckheim, and Sars cited with four different 

 sets of initials it seemed clear was intended for George Ossian Sars. 

 A few citations have been added by the editor from original sources. 

 Those interested will not fail to collect others from the Biblioiheca 

 Zoologica and similar publications. Under the Cladocera the citations 

 had to be given in the original form, because the data given in the 

 manuscript did not make possible a more definite reference. In these 

 cases all but the references to synonyms were cut out. 



In accordance with the rules of nomenclature of the German Zoo- 

 logical Society, the comma between the specific and author's names 

 has been eliminated and all specific names appear in lower case. So 

 far as possible these rules have been followed in other respects. The 

 absence of literature, however, made it unsafe for me to touch doubt- 

 ful cases. 



The "sp. n." of the old report has been replaced by the author's 

 name, Herrick. 



The various "keys" have been reduced to a uniform plan, and 

 several of them have been compiled by bringing the sections together 

 from various parts of the manuscript. To increase the value of these 

 "keys," the page upon which the description of the genus or species 

 begins has been added and names of authors and other details have 

 been dropped. 



The names of families, genera, etc, have been italicized in the gen- 

 eral text. 



The order and arrangement of the plates is most unsatisfactory. 

 None of the drawings had been called for by me before they were sent 

 to the engraver, and besides the necessity of using so many of the old 

 plates made an orderly and respectable arrangement impossible. 



The index is wholly the work of the editor. 



Professor Turner's paper practically appears in its original shape. 

 The key to the Cyprididte was changed from the bracket form to the 

 paragraph form for practical reasons only. 



I take this opportunity to express my indebtedness to Professor 

 C. Judson Herrick of Granville, Ohio, for kindly looking after the 

 engraving and printing of the plates, and to Mr. W. H. Kussmaul of 

 Granville for the care he exercised in the printing of the plates. To 

 the state printing expert, Mr. George C. Stevens, I am indebted for 

 indulgent considerations and a lasting patience. 



HENRY F. NACHTRIEB. 



AfKiL 29, 1895. 



