贵州北部在晚奥陶世五峰组之上与早志留世龙马溪组之间常发育一套厚度不大的,岩性不一的介壳相地层(为壳相的泥灰岩或页岩),通常含三叶虫小达尔曼虫(Dalmaniti- na),腕足类、腹足类化石,有时富含单体瑚瑚化石,这段地层,过去我国地质界一般称为 Dalmanitina 层,或称观音桥组。观音桥组的化石首先由张鸣韶、盛莘夫于1940年调查 In the northern part of Guizhou, a set of medium-thickness lithofacies (marl or shale) of small thickness and lithology are usually developed between the Late Ordovician Wufeng Formation and the Early Silurian Longmaxi Formation. Commonly contains Trilobite small Dalmatian insects (Dalmanitina), brachiopods, gastropods fossils, and sometimes rich in monomer coral fossils, this formation, past the geology of our country commonly known as the Dalmanitina layer, or the Guanyin Bridge group. Guanyinqiao fossils of the first group by Zhang Ming-shao, Sheng Xin husband investigation in 1940