Several specimens of Opisthobranch mollusc of the genus Haminoea were collected from Madh Island (Bombay) during December 1974 and January 1975. The external characters of these specimens differed from those of the recorded characters of the two species (Haminoea tenera and H. crocata) known from India. The main differences were seen in spawning behaviour, the radula and the nature of the substratum. The biology and the reproduction were also studied in the laboratory. The anatomical features are primitive and simple, typical of an opisthobranch of a herbivorous feeding habit