Two species of the genus Ruditapcs (Mollusca, Lamellibranchia， Veneridae) viz,R. philippinarum (Adams et Reeve) and R. variegata(Sowerby) are found off China coast，the former species being very abundant and wide1y distributed in our coasts，and is also an important species for culture. For many years, there has been some confusion with regard to the taxonomic distinction between these two species in our country. With an aim of clearing up such a confusion， we re-examined a total of 3,730 specimens. A carefu1 study is made not only on the difference in external shell morphology, but also on the difference of the mantle and mant1e fusion, outer and inner demibranchs，labial palp, siphon, and the shape of the s.perm of these two species. The comparative morphological structure of these two species (P1ate Ⅰ-Ⅲ) clear1y show that they are two distinct species. These two species also have different 1imits of distribution. Ruditapes philippinarum is found as north as the Bohai Sea, its southern 1imit is in the Guangdong continental coast in the South China Sea, but it is noticeab1y absent in Hainan Is1and and the Beibu Gulf. R. variegate has its northern limit of distribution in Pingtan (Fujian Province) in the East China Sea, and has a southward distribution extending to the southern tip of Hainan Is1and and to the Beibu Gulf.