Rafinesque, 1814
Body firm, muscular. Mantle in larvae, juveniles, and males widely-ovoid, in females narrower. Mantle fused with head, connected with funnel by well-developed, strong connective apparatus. Ventral mantle in females covered by set of skin tubercles connected by skin ridges in a reticulate pattern, other parts of body and entire body in males smooth. Head wide, weakly separated from mantle and arms. Eyes large. Mantle opening wide, reaching level of upper eye margin. Funnel long, conical, extending beyond bases of 4th arms, not sunken into tissues. Skin pores (water pores) beside funnel near bases of both 4th arms. Arms short in larvae, long and thin in juveniles and adults, 1st and 4th subequal, much longer than 2nd and 3rd. Web and arm membranes almost absent. Suckers small, numerous, 3 primary ones small, in one row, others in 2 rows. Ink sac present, photophores absent. Males significantly smaller than females. Third right arm hectocotylized, in larvae and juvenile males appearing as a stalked sac. Hectocotylus develops inside sac, released at maturity, detached during mating. Females have a unique buoyancy apparatus inside the dorsal mantle resembling a fish swimming bladder. 19-20 lamellae per demibranch. Females ovoviviparous, incubate eggs (>100,000, 1.8 mm in length, 1.0 mm in width) up to hatching. In adults upper side of body deep-blue, lower side rose-violet with silvery metallic iridescence. Larvae distinguishable by long 1st and 4th, short 2nd and 3rd arms, males also by characteristic appearance of hectocotylus. Reticulate pattern on ventral mantle evident in juveniles at ML approx. 10 mm, water pores at all stages. Ventral mantle in larvae clear. ML of females up to 31 cm, of males to 3 cm.
Adults live near the surface, males commonly in empty tests of salps or doliolids.