Parietal eye

A parietal eye, also known as a third eye or pineal eye, is an eye located at the top of the head. Reptiles, amphibians have this eye. The third eye is always smaller than the main paired eyes.Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 471–473 In living species, it is always covered by skin and is not visible externally. 

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Category:Eye