The Late Ordovician Wufengian sediments in western Zhejiang include three facies: 1) graptolite shale facies, composed of two parts--the upper part the Yankou Formation, with the Diplograplus bohemicus(graptolite) zone and Dalmanitina sp.(trilobite), and the lower part the yuqian Formation with four graptolite zones:(4) the Paraorthograptus yuqianensis zone,(3) the Climacograptus venustus zone,(2) the Dicellograptus szechuanensis zone and(1) the Pseudoclimacograptus anhuiensis zone; 2) mixed facies, consisting of the Wenchang Formation in its upper part and the Changwu Formation in its lower; and 3) shelly limestone facies, whose upper and lower parts are separately the Wenchang Formation and Sanjushan Formation, containing Taeniolites, Proheliolites, etc. In this region the Dalmanitina-Hirnantia bed is well exposed,and Da. and H. are associated with Diplograptus bohemicus, belonging to the late Late Ordovician.The Ordovician-Silurian boundary is drawn as follows:(1) for the graptolite facies, it lies between the Diplograptus bohemicus zone and Glyptograptus persculptus zone;(2) for the graptolite-sheny limestone facies(brachiopod fauna), it is placed between the top of the Diplograptus bohemicus zone and the base of the horizon with the Eospirifer fauna; and 3) for the shelly facies(brachiopod fauna), it is drawn between the top of the horizon with the Dalmanitina-Hirnantia fauna and thebase of the horizon with the Eospirifer fauna.