One specimen of Argonauta argo belonging to the family Argonautidae, was collected Songjeong, southeastern coastal water of Korea on July 12, 2010. The specimen, a mature female of 76 mm mantle length and 97 mm shell length. The number of ribs are 56 in shell. The shell is distinct between the arm Ⅰ's. The Ⅰ arm has expanded, hemi-discoidal web to which the distal part is fused together. The funnel is large and exceeds the base of arm Ⅳ. The arms formula is Ⅳ > Ⅱ ≒ Ⅲ > Ⅰ. The specimen was female. Fecundity was 155,203 eggs. This species is pelagic octopus and important prey item of dolphin.
