Wikipedia
Vitreledonella richardi, also known as the glass octopus, is an incirrate octopus. It is the sole representative of the genus Vitreledonella and of the family Vitreledonellidae.
Vitreledonella is a transparent, gelatinous, and almost colorless meso- to bathypelagic octopod found worldwide in tropical and subtropical seas with a mantle length (ML) up to 11 cm and a total length up to 45 cm in adults. The upper three pairs of arms are subequal in length; in juveniles about as long as the mantle, in adults two to three times ML. The fourth, ventral pair is slightly shorter. Suckers are small, widely separated, and in a single series. In males, the left arm III is hectocotylized, with a spherical vesicle near the tip, but is not detachable. Eyes are nearly rectangular in shape as seen from the side. The radula is heterodont, also known as heteroglossan, in which the middle or rhachidian tooth is each array has multiple cusps and the lateral teeth are unicuspid.
Vitreledonella is ovoviviparous. The female broods her eggs, of which hundreds are within the mantle cavity. Each egg measures about 4 mm in length. Newborn larvae have a ML around 2.2 mm.
Amphitretus and Bolitaena are two other transparent, gelatinous pelagic incirrate octopods. Both of these genera differ from Vitreledonella in that the right third arm is hectocotylized and the radula is ctenodont (with comb-like individual teeth).