NORTH AMERICAN PARASITIC COPEPODS BELONGING TO THE FAMILY ERGASILID^. By Charles Branch Wilson, Department of Biology, State Normal School, Westfield, Mass. INTRODUCTION. The present is the tenth'* paper in the series based upon the collec-tion of parasitic copepods in the U. S. National Museum, and deals with the family Ergasilidse. As in all the preceding papers, the Museum material has been largely supplemented by a study of living forms, developmental stages, and material derived from other sources. Much of this study has been accomplished while working for the U. S. Bureau of Fisheries at various laboratories situated both upon salt and fresh water. For these valuable opportunities the author is indebted to the courtesy of the Hon. George M. Bowers, U. S. Commissioner of Fish and Fisheries, to whom acknowledgment is gratefully made. Thanks are also due to Prof. E. A. Birge and Prof. Chauncy Juday, of the University of Wisconsin, for furnishing a generous supply of tow taken from Lake Mendota, Madison, Wisconsin, from which has been obtained an excellent series of specimens of both sexes of Ergasilus cliautauquaensis. The value of this material is enhanced by the fact that it was the first opportunity for a personal examination of an Ergasilus male. To Dr. Andrew Scott, of the Board of Fisheries of Scotland, the author returns sincere thanks for some finely preserved specimens of oThe nine preceding papers are 1. The Argulidse, Proc. U. S. Nat. Mua., vol. 25, pp. 635-742, pis. 8-27. 2. Descriptions of Argulidse, idem, vol. 27, pp. 627-655, 38 text figures. 3. The Caliginse, idem, vol. 28, pp. 479-672, pis. 5-29. 4. The Trebinse and Euryphorinse, idem, vol. 31, pp. 669-720, pis. 15-20. 5. Additional Notes on the Argulidse, idem, vol. 32, pp. 411-424, pis. 29-32. 6. The Pandarinse and Cecropinse, idem, vol. 33, pp. 323-490, pis. 17-43. 7. New species of Caliginse, idem, vol. 33, pp. 593-627, pis. 49-56. 8. Parasitic Copepods from the Pacific Coast, idem, vol. 35, pp. 431-481, pis. 66-83. 9. Development of Achtheres ambloplitia Kellicott, idem, vol. 39, pp. 189-226, pis. 29-36. Proceedings U. S. National Museum, Vol. 39— No. 1788. 263
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