The specimens referred to the Lungmachi Formation graptolites in the present paper were collected from Sanlangpu of Xixiang, Southern Shaanxi, consisting of 8 genera and 51 species or subspecies including 12 new species (see Table l in the Chinese text). This paper describes only the new species, with the rest being shown in tablesand plates. According to the present data on hand, the Lungmachi Formation graptolites studied here may be divided into 4 zones as follows:4. Orthograptus vesiculosus Zone (L₃)3. Parakidograptus acuminatus Zone (L₂)2. Glyptograptus persculptus Zone (L₁)1. Diplograptus bohemicus Zone (W₆)The first graptolite zone belongs to the Upper Ordovician, while the others to the Lower Silurian, indicating that the Lungmachi Formation in our studied area is a lithostratigraphic unit stridling across the Ordovician-Silurian boundary.This paper is in commemoration of the respectable late Prof. Mu En-zhi, to whom the writers are very much obliged for his kindness inguiding their scientific researches.