System Glossary
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Definition of Term

spectacle
(English) A transparent membrane covering the eye. Petromyzontidae have a primary spectacle that is an unattached modification of the cornea while other fishes may have a secondary spectacle formed from skin originally fused to the cornea and subsequently separated. The secondary spectacle is found in fish that live in habitats with abrasive substrates or in fish with protruding eyes that require some streamlining.

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