INTRODUCTION The genus Nicothoe has been known until recently only from its type species, N. astaci Audouin & H. Milne-Edwards, 1826. This species is parasitic on the European lobster, Homarus gammarus (L., 1758), and has received a good deal of attention, in view of the economic importance of its host. Very recently, however, another species, N. analata Kabata, 1966, was described from a decapod host of another genus, Nephrops. Attached to the gills of N. sinensis Bruce, 1966, this parasite was discovered in the South China Sea. The two species differed only in the shape of the trunk, their appendages being identical in all respects. Since the discovery of N. analata, its discoverer, Dr. A. J. Bruce, has been engaged in the study of various species of Nephrops from different parts of the world. His studies brought to light abundant Nicothoe material. The author has been given the opportunity to examine this material and has found that it contained two more new species of Nicothoe. The examination afforded also an opportunity of a closer study of the appendages of this genus. Such an opportunity was very welcome, since the description of N. analata had to be based on the study of a single specimen. The present paper presents the results of this work. It contains comments on the previous description of the appendages (Kabata, 1966) and describes two new species: N. brucei and N. simplex. The methods employed in this study were similar to those used in the previous paper. COMMENTS ON THE APPENDAGES As mentioned above, the appendages of Nicothoe analata have been found to be identical with those of N. astaci. The same proved true for the new