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
Humboldt squid fished commercially, predominantly in Mexico and Peru. Some squid may grow to in mantle length and weigh up to . Generally, the mantle (or body) constitutes about 40% of the animal's mass, the fins (or wings) about 12%, the arms and tentacles about 14%, the outer skin about 3%, the head (including eyes and beak) about 5%, with the balance (26%) made up of the inner organs. Humboldt squid are carnivorous marine invertebrates that move in shoals of up to 1,200 individuals. They swim at speeds up to propelled by water ejected through a hyponome (siphon) and by two triangular