\u3ci\u3eGyrodactylus eucaliae\u3c/i\u3e n. sp. (Trematoda: Monogenea) from the Brook Stickleback, \u3ci\u3eEucalia inconstans\u3c/i\u3e*

A new species of Gyrodactylus was observed on the skin, gills, and fins of the brook stickleback from the English Coulee, Grand Forks, North Dakota during the summers of 1953-1955. Host-specificity is usually striking in the monogenetic trematodes and since this parasite was not observed on any other species of fish from this body of water or the nearby Turtle River, it was studied in detail and is here described as a new species, G. eucaliae