Trilobite eyes were typically compound, with each lens being an elongated prism. The number of lenses in such an eye varied: some trilobites had only one, while some had thousands of lenses in a single eye. In compound eyes, the lenses were typically arranged hexagonally. The fossil record of trilobite eyes is complete enough that their evolution can be studied through time, which compensates to some extent for the lack of preservation of soft internal parts.
Trilobite eyes were typically compound, with each lens being an elongated prism. The number of lenses in such an eye varied: some trilobites had only one while some had thousands of lenses in a single eye. In compound eyes the lenses were typically arranged hexagonally. The fossil record of trilobite eyes is complete enough that their evolution can be studied through time, which compensates to some extent for the lack of preservation of soft internal parts.