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. 1
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