European squid propulsion. The posterior border is slightly concave. The head is relatively small and has large eyes which are covered with a transparent membrane. Like almost all squid, this species has ten limbs surrounding the mouth and beak: eight are relatively short arms, and two, which form the tentacles, are long, as they are used to catch prey. The fourth left arm of males is a hectocotylus. The European squid can grow up to 30–40 cm in the mantle length, but more usually they are 15–25 cm long. The males are generally bigger than the females and exhibit more rapid rates
Whip-lash squid and "Idioteuthis" are known to have expanded tentacular clubs as paralarvae (for both species) or adults ("Idioteuthis"). Members of this family have scarcely been observed in life, but at least two species ("Mastigopsis hjorti" and "Magnoteuthis magna") are known to hover above the ocean bottom in a vertical orientation, the head pointing downward. The squid use their large fins to maintain this orientation and use both their extended tentacles like fly paper, held rigidly at a constant distance apart: this has been termed the "tuning fork" position. Prey items apparently consist primarily of benthic crustaceans. Although mastigoteuthids possess ink sacs