Large umbilical aperture without lip. Surface rather rough from numerous spine collars. Aposymbiotic.
Ref.: Boltovskoy (1973), Fèbvre-Chevalier (1971), Malmgren and Kennett (1976, 1977, 1978), Kennett (1976), Kahn and Williams (1981), Caulet et al. (1992), Thiede and Jünger (1992), Puechmaille (1994), Kroon and Darling (1995), Ortiz et al. (1995), Rohling et al. (1995), Gupta and Mohan (1996), Spero and Lea (1996), Schiebel et al. (1997).
Distribution: Abundant in subpolar and, to a much lesser extent, polar water masses. In tropical areas it favors nutrient-rich upwelling waters, where it can reach high concentrations (e.g., near the coastal upwelling off Namibia and toward the eastern equatorial upwelling region, where phosphate and nitrate concentrations are higher than in other parts of the tropical and subtropical South Atlantic, cf. 30 m water depth annual means in Levitus and Boyer, 1994).