Record and Habitat. I am indebted to Dr Theodore Monod of Paris for his kindness in sending me four female specimens of Basanistes huchonis (Schrank) which, according to him, is common on Salmo hucho on the inner side of the operculum, in the rivers of Continental Europe. In 1928, Parasitology, 20, 183, I gave an account (in which by an error the specific names of the host and parasite were unfortunately interchanged) of the external features, with figure, from the single specimen in the British Museum, which it is unnecessary to repeat here. As the Museum specimen lacks a bulla and the appendages of Basanistes, owing to its apparent rarity, have not been adequately described, I append the following account. The male is still unknown.