Ram's horn squid

Spirula spirula

Family Spirulidae - squids

Body (mantle) cylindrical, short, rounded tip; color reddish brown to pale pink; posterior end (tip) with 2 small rounded fins; 4 pairs of short arms and 1 pair of longer tentacles; arms and tentacles with suckers; internal shell is tubular, tapered at one end, spiraling, spirals not touching or barely touching, chambered, aperture round, covered inside except for small hole that leads to next chamber, color yellowish white; live specimens rarely seen; internal shell is gas-filled and may wash ashore on beaches.
Similar Species
The ram's horn squid is smaller and squattier than squids in the Loliginidae family, and most people will never see a live one. The internal shell can be distinguished from spiraling gastropod shells by it chambers. Gastropods live in their shells, so the shells won't be chambered.
Gulf, deep waters
Maximum Size
squid 4.5 cm (1 3/4 in) mantle length, internal shell 2.5 cm (1 in)
Other Common Names
little post horn squid, tail light squid
Previous Scientific Names
The ram's horn squids spend most of their lives in a heads down position. The gas-filled internal shell keeps the posterior end up. These squids also have a light-emitting organ between the 2 posterior fins (hence, the name tail light squid).