Scopelarchus analis

Scopelarchus analis, the short fin pearleye or blackbelly pearleye, is a species of fish that can be found circumglobal in warm waters. It is a member of the Scopelarchus, a genus of pearleyes.

Size
This species reaches a max length of 4.96 in.

Biology
It has a unique cylindrical eye that it is directed dorsally. This allows the fish to gain a binocular view of the water column above. The fish also possesses a unique adaptation where it has multiple retinae. The primary retina is located at the base of the cylinder, an accessory retina along the nasal wall, and between the two is a retinal diverticulum.