A SYNOPSIS OF THE SPECIES OF BOECKELLA AND PSEU- 

 DOBOECKELLA WITH A KEY TO THE GENERA OF THE 

 FRESH- WATER CENTROPAGIDAE. 



By C. DwiQHT Marsh, 



Of the United States Department of Agriculture. 



The fresh-water genera of Centropagidae are of a great deal of 

 interest because of the rather restricted distribution of many of the 

 species, and a thorough study of these animals from a morphological 

 standpoint is likely to throw much light on their phylogeny and 

 furnish valuable data for the theories of geographical distribution. 

 For this study it is not only helpful but also necessary to have a 

 synopsis giving the species characteristics in a fairly complete but 

 brief form. Giesbrecht and Schmeil's Copepoda Gymnoplea, pub- 

 lished in 1898, did this in an admirable manner; many publications 

 have been issued since 1898, however, and new species and genera 

 have been added. The author has had in mind the preparation of 

 synopses of the fresh-water genera of copepods, and the present 

 paper is a contribution to that end. This pubUcation has resulted 

 from a personal need of a synopsis of the genera Boeckella and Pseu- 

 doboeckella. 



It is perhaps not necessary to go into a discussion of the morpho- 

 logical relations of Boeckella and Pseudoboeckella. This has been done 

 at some length by Ekman, 1905, and the author accepts his conclu- 

 sions. Pseudoboeckella Mrazek differs from Boeckella DeGuerne and 

 Richard by the fact that the endopodite of the right fifth foot of the 

 male is always 3 segmented with the distal segment armed with setae. 

 It is possible that the differences between Boeckella and Pseudohoeck- 

 ella should hardly be considered of generic value, but the distinction 

 is a convenient one, and it seems wise to use the two generic names. 



KEY TO THE GENERA OP THE CENTROPAGIDAE OF FRESH WATER. 



Endopodites of feet 1-5, 2 segmented Calamoecia Brady. 



Endopodites of feet 1-4, 1 segmented 2 



Endopodites of feet 1, 1 segmented ; 2^, 2 segmented 3 



Endopodites of feet 1-4, 3 segmented 4 



Endopodites of feet 1-5, 3 segmented 6 



Endopodites of feet 1, 2 segmented; 2-4, 3 segmented, endopodites female 



fifth feet, 2 segmented 8 



No. 2498.— Proceedings U. S. National Museum, Vol. 64, Art. 8. 



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