The eyes and the orbits of 2 species of fishes with "dorsal eyes".

The eyes of 2 species of fishes with dorsal eyes Uranoscopus oligolepis and Paralichthyes olivaceus were studied. In the Uranoscopus, ciliary projections were not conspicuous and in the Paralichthyes, the projections were small. 3 types of photoreceptors were observed in both species--rods, single cones and twin cones. In both species, the number of twin cones increased towards the central retinae and in the Paralichthyes, the single cones also increased in number. The rods were lowest in the central region. In the orbit, both species displayed complex solid bones. For example, the lateral border of the orbit was a complex formed by the lacrimal, suborbital, postorbital and parietal. In the Paralichthyes, the lateral orbital border was actually continuous with the orbital and parietal bones and the border was not distinct. The formation of fused plates would serve to restrict eye movement as well as to resist deep sea pressure acting from above.