The Mesozoic freshwater molluscs described in this paper were from the provincesof Shantung,Shensi,and Kansu.The Shantung specimens were collected in 1951 by theLaboratory of Vertebrate Paleontology at Chinkongkou,Laiyang,Shantung in associationwith the dinosaur bones.Those from Shensi and Kansu,which comprise the greaterportion of the material in the collection,were collected from the Northwestern Provincesduring the year 1952,and sent for study by the Bureau of Petroleum Exploration.Thepresent paper gives a description of the new forms together with a brief discussion of thestratigraphy of the fossil-bearing formations