Haeckel
Diagnosis: Spherical, ovoidal, pear- or spindle-shaped shell, with triangular mesh openings of various sizes. Radial tubes about as long as tangential bars, sometimes longer on one pole, proximal portions with one or a few single lateral thorns, distal portions with 2 whorls of 2-6 branches, sometimes distally forked, with spathillae. Terminal whorl with shorter branches, inner whorl branches about twice as long, branches of the two whorls alternate positions.
Two subspecies of this species have been reported from the South Atlantic: A. b. ovulum Borgert (whorls widely separated, 2-4 branches per whorl; Aulosphaera bisternaria ovulum) is considered a warm-water species, and A. b. septentrionalis Borgert (whorls narrowly spaced, 3-6 branches per whorl; Aulosphaera bisternaria septent) is normally reported from the Antarctic.
Diameter: 1.8-5.5 mm.