Worldwide warm waters: Cape Cod to Bay of Biscay, Caribbean to Mauritania, NW. Indian Ocean, Uruguay to S. Africa, Mascarenhas & S. Indian Ocean, NW. Pacific, SW. Pacific. Absent in Red Sea, China Sea, and in all the Mediterranean east of Alborán.
 
« This is a mesopelagic species, inhabiting from 600 to 700m during the day and found » because of its hunting patterns, « in depths less than 300m at night. Capture of young at depths between 1000 and 1750m suggests that females possibly lay eggs on the bottom of continental slopes  » (Reid in Jereb & Roper, 2005).

Reid: « Spirally coiled internal shell located in posterior end of animal; shell comprised of over 30 chambers in adults. » The chambers are connected by a siphuncle (or “siphunculus”: a cylindrical canal perforating the partitions in polythalamous shells – T. Brown: The elements of conchology, London 1816). « This shell serves as a hydrostatic system, allowing the animal to control its buoyancy » (animaldiversity.org).

« It is easy to imagine, however, that in thus developing itself round an axis, the successive whorls may or may not actually touch one another. The common Spirula is an example of the latter structure in a recent shell ; and the shell called Crioceratite corresponds with the Ammonite, much as the Spirula corresponds with the Nautilus. » – D. T. Ansted: The ancient world, London 1847.

Spirula spirula dredged « off Grenada in the Caribbean by the “Blake” from a depth of 950 fathoms. » The shell appears at right. As it contains some air, its position in the rear part of the animal inclines this one, by default, upside down. Image taken from “Three cruises of the ‘Blake’ – XVIII Cephalopods”, Bull. of the Museum of Comparative Zoology at Harvard College vol. XV, Cambridge (Mass.) 1888.