These 22 points are divided into two groups, which,represent respectiyely, two graptolite types in the early ordovician, namely, the South China type and the Central China type.

• 在平面图中,22个点可划分为2个点群,分别代表中国早奥陶世的两大笔石动物群,即华南型笔石动物群和华中型笔石动物群。