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Trilobites had unique eyes, because they were made of calcite? (Calcium carbonate - CaCO3?). Pure forms of calcite are transparent, and the trilobites used clear calcite crystals to form the lenses of their eyes. In this, they differ from most other arthropods, which have soft eyes. The trilobite eyes were compound, with each lens being an elongated prism. The number of lenses in such an eye varies however, some trilobites had only one, and some had thousands of lenses in one eye. In these compound eyes, the lenses are arranged in a hexagonal way (nature's way of close packing). Of course there's never a rule without an exception, and to prove that there were blind trilobites as well. |
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Further reading *Trilobite! - Richard Fortey (ISBN 0 00 257012 2 (amazon.com, search)) *http://www.aloha.net/~smgon/ordersoftrilobites.htm |
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