Abstract: The systematics and bionomics of the Salangid fishes of Lake Taihu are dealt with in this paper.The species concerned are 4 in number;viz., Reganisalanx brachyrostralis(Fang),Protosalanx hyalocranius(Abbott), Neosalanx oligodontis,sp.nov.and Neosalanx tangkahkeii(Wu)var.taihuensis,var.nov.The diagnoses of the new forms are as follows: Neosalanx oligodontis,sp.nov.—Total length 42—48 mm;depth 7.4—9.5 in standard length,head 6—7.2;snout 3—4.6 in head;a single row of minute teeth on the premaxillary and maxillary;mandible,tongue and palatine toothless;vertebrae 50-53;ripe eggs with external filaments;distance between the origin of the dorsal and the tip of the snout 2.7 times the distance between the base of the dorsal and that of the caudal;distance between the base of the ventral and the origin of the anal about equal to the distance between the bases of the ventral and pectoral;one black patch on each caudal lobe and a similar patch on the anal near the base in males;D.2,9-11; A.3,19-23. Neosalanx tangkahkeii(Wu)var.taihuensis,var.nov.—Differs from typical N. tangkahkeii in having no black blotches on the caudal lobes and no black dots at the tip of the snout as well as along both sides of the ventral surface of the body. Regarding Protosalanx hyalocranius,some important characters,such as the presence of a swim-bladder with a pneumatic duct,the presence of the ventral longitudinal skin fold and the fan-shaped pectoral fins,have been particularly noticed.Young Protosalanx has as pointed a snout as the adult, and not a blunt one as believed by some earlier workers,who in all probability had mistaken the member of Neosalanx for the young of Protosalanx. Sex ratio,breeding season,fecundity and some peculiarities in the re- productive system have also been investigated for the four species.Result of year-round observation suggests that 3 of these species are permanent freshwater residents.In the lapse of about 6 months after hatching these Salangids grow to a full size.Individuals of one year old attain sexual maturity and death ensues shortly after spawning.