XIII. NOTES ON CRUSTACEA DECAPODA IN THE INDIAN MUSEUM. IX. LEANDER STYLIFERUS, MiI.NE-EdWARDS, and REIyATED FORMS. (Plates VIII— X). By Stanley Kemp, B.A., Superintendent, Zoological Survey of India. One of the most conspicuous features of the fauna of the silt-laden waterways of the Gangetic delta and other estuarine regions of the Indian coast is the enormous abundance of prawns belong-ing to the genus Leander. In general appearance the forms that frequent these localities differ widely from the marine species on which our conception of the genus is primarily based ; the rostrum is much longer, with an elevated dentate crest at its proximal end, the second legs are very slender, often with the palm of the chela inflated, and the last three legs are attenuated. Leander styliferus, described by Milne-Edwards eighty years ago from specimens ob-tained at the mouth of the Ganges, is typical of the species that exhibit these characteristics. The group of species, though it appears to be a natural one, is by no means clearly defin-«d, for it grades almost imperceptibly into the more normally constituted elements of the genus, through such forms as Leander concinnus, de Man, and L. indicus, Heller. It is, however, of particular interest in the study of the brackish water fauna of Eastern Asia in that it includes a number of abun-dant species that migrate annually from the sea into estuaries and tidal rivers, as well as others that have succeeded in establishing themselves in pure fresh water. Some of the forms are of considerable economic importance in India and China, and probably also in other countries. Vast quantities of Leander styliferus and L. tenuipes are caught in the Gangetic delta and sold in those markets frequented by the poorer classes of the population, while in the Kiangsu province of China L. modestus is captured in large numbers, especially in the Tai Hu Lake. To a European palate these species of Leander are lacking in flavour and seem greatly inferior to the Penaeidae that frequent the same waters. Among the Carids that have been accumulating in the Indian Museum for the past thirty years, the species of Leander allied to L. styliferus are well represented and the collection has recently been enriched by the acquisition of a number of specimens, com-prising several forms of great interest, obtained by Dr. Annandale in China and in the Malay Peninsula.