Abstract: A left upper molar (IVPP VI 1197) and a fragment of lower jaw, two vertebrae and some ribs (V 12180) were collected from Formation I of the Buxin Group in Sanshui Basin, Guangdong Province, China. The lower jaw is more similar to that of Bemalambdidae than to other mammals as evidenced by its robust body, deep mandible symphysis with rather steep anterior border, presence of three pairs of incisors, a large c and especially a long diastema between c and p2, which is one of the distinctive features of Bemalambdidae. The upper molar is also similar to that of the Bemalambdidae in being proportionally wide and short, with a wide stylar shelf, developed parastyle and metastyle, and a V —shaped protocone. The specimens from Sanshui are more similar to those of Hypsilolambda than to Bemalambda in lacking a distinct antero —external border on the lower jaw and having a forked and V —shaped parastyle on the upper molar. Hypsilolambda is known to include two species: H. chalingensis and H. impensa. The Sanshui specimens are much larger and robuster than both of them. The molar is also much wider in proportion. They may represent a new species of Hypsilolambda, or even a new genus, At present we tentatively assign it to Hypsilolambda as？Hypsilolambda sp. The deposits bearing the mammal fossils was named as Formation I of the Buxin Group. Recently it was suggested to be transferred to middle Eocene Baoyue Formation. The Bemalambdidae are only known from early一middle Paleocene. Hypsilolambda is only known from middle Paleocene. Therefore, the age of the fossil一bearing deposits is unlikely Eocene, but Paleocene. As for the stratigraphic terminology of the deposits, it seems better to keep the original one, Formation I Of the Buxin Group.