Abstract: Sinacanthus wuchangensis was erected by P 'an Kiang (Jiang) in 1957 on some fin spines from Wuchang, Hubei Province. Seven years later, more than 10 fin spines of Sinacanthus wuchangensis from Devonian System (?) of Wuchang were studied again by the same author, and the characters of Sinacanthus were analyzed thoroughly. Subsequently, similar fin spine fossils were discovered one after another in the middle-lower reachs of the Yangtze River (Yangtze region), such as Sinacanthus of Jiujiang, Jiangxi Province (Li et al., 1966); Sinacanthus fancunensis from Tangjiawu Formation of Ningguo, S. Anhui (Liu, 1973); Sinacanthus wuchangensis, Smacanthus triangulatus, Sinacanthus fancunensis from Guodingshan Formation of Hanyang (Pan et al., 1975) and Sinacanthus cf. wuchangensis from Fentou Formation of Puxi, Chongyang, Hubei Province (Li, 1978; 1980); Sinacanthus sp. from Fentou Formation of Chaoxian, Anhui Province (Wang et al., 1980); Acanthodii fron Rongxi Formation of Dayong, NW Hunan (Zeng, 1988) etc.. The Sinacanthus fossil localities were restricted to the Yangtze region before the discovery of the Tarim fossils. They used to be referred to as Devonian or Early Devonian in age, but later discoveries have demostrated that the age of Sinacanthus-bearing beds should be Silurian (Li, 1980). In 1988, five Sinacanthus fossil beds were found in the Tataertag Formation of Kalping, NW Tarim and the age of the Tataertag Formation was considered MiddleLate Silurian (Table 2). In the summer of 1992, Wang Junqing, Zhu Min and the author of this paper found a lot of fossil fin spines in both Kalping and Bachu, NW Tarim. Some of them were preseved together with agnathans Hanyangaspis etc..Most of these fin spine specimens were collected from Imogantau Formation of Bachu.