Abstract: A new species of Alloptox is described in this paper. All the material was ga thered from three localities (Songlinzhuang, Zhengji and Shuanggou) of Sihong County, Jiangsu Province. For detailed information on geological and stratigraphical background and others the reader is referred to Li et al. (1983) and Qiu and Lin (1986). Almost all here described 113 specimens (Songlinzhuang 68, Shuanggou 27, Zhengji 18) are isolated teeth with exception of three fragments of upper and lower jaws with few teeth. All specimens of these three localities are treated as members of one and the same population. However the measurements and figures of specimens from each locality are separately represented. The figures are represented as left ones, the abbreviated word "inv. is used under the figures of right teeth. All specimens are stored in IVPP under the inventory numbers V 8840—8842. The present paper is one of the series studies of Xiacaowan Fauna of Miocene from Sihong. In all previous papers the fauna was assigned to Middle Miocene. Qiu et al. (1990) adapted the boundry between early and middle Miocene to'; the European one. Therefore Xiacaowan fauna was reassigned to Early Miocene. I am very grateful to Prof. Wang Banyue for showing me the specimens of Sinolagomys cf. ulungurensis for comparison. Thanks are due to my colleagues: Profs. Wang Banyue, Tong Yongsheng, Qiu Zhuding and Zheng Shaohua who critically read the manuscript.