三叶虫类

像三叶虫和腕足类一样的贝壳类生物是谁的祖先在岩石中得到一点提示，这些东西到处都是。

Shelly creatures such as trilobites and brachiopods , of whose ancestors there is little sign in the rocks , are suddenly everywhere .

早志留世轻变质碎屑岩地层时代的确定主要依据三叶虫、头足类和珊瑚等大化石，一直没有微体化石方面的证据。

The determination of the stratigraphic age of the Lower Silurian low-grade metamorphic clastic rocks was mainly based on trilobites , corals and cephalopods , but no evidence of microfossils has been found .

本文根据古生物学、现代生物学和生物进化论研究成就，就无脊椎动物起源、三叶虫、头足类、昆虫进化过程中的模糊问题作了逻辑推理思考。

Based on the achievements in paleontology and modern biology and evolutionism , this paper makes a inferential thought on some indistinct questions about origin of invertebrate , trilobites , cephalopoda and insect in course of evolution .