Science. 1973 Mar 9;179(4077):1007-9. doi: 10.1126/science.179.4077.1007.
The corneal lenses preserved in the eyes of some of the Paleozoic trilobites (Arthropoda) are constructed of calcite that is crystallographically oriented to behave like glass. The calcareous lenses are capable of forming inverted images over a large depth of field and must have been present in the living trilobites.
一些古生代三叶虫（节肢动物）眼睛中保存的角膜透镜由方解石构成，其晶体结构使其具有玻璃般的特性。这些钙质透镜能够在较大的景深范围内形成倒置的图像，并且在活的三叶虫中肯定存在。
