Shell nearly three-sided pyramidal, slender, smooth. Length of the three joints = 1 : 2 : 2, breadth = 1 : 4 : 4. Cephalis hemispherical, with two oblique, conical horns of nearly equal length. Thorax nearly hemispherical, with slightly prominent crests, and with subregular, hexagonal pores. Abdomen of about the same length, with much smaller, irregular, roundish pores, forming three convex, nearly circular lobes between the three large divergent feet. These are slender, three-sided pyramidal, longer than the shell, fenestrated at the thickened base, with some rows of larger pores; their back is slightly concave.
Dimensions.—Length of the three joints, a 0.02, b 0.04, c 0.04; breadth, a 0.02, b 0.08, c 0.09.
Habitat.—South Pacific, Station 295, depth 1500 fathoms.
13. Pterocanium trilobum, Haeckel.
Dictyopodium trilobum, Haeckel, 1882, Monogr. d. Radiol., p. 340, Taf. viii. figs. 6-10.
Shell three-sided pyramidal, nearly tetrahedral, covered with conical spines. Length of the three joints = 1 : 4 : 2, breadth = 1 : 6 : 10. Cephalis hemispherical, with a large conical horn (as long as the thorax). Thorax tetrahedral, with little prominent crests. Abdomen forming three semicircular, convex lobes between the three feet, half as long as the thorax, with the same irregular, roundish pores. Feet slender, about as long as the shell, triangular, with convex back, strongly divergent, fenestrated at the inflated and thickened base. (Compare the special description of the living form and its soft body in my Monograph.)
Dimensions.—Length of the three joints, a 0.02, b 0.08, c 0.04; breadth, a 0.03, b 0.12, c 0.2.
Habitat.—Mediterranean, Messina, surface.
Genus 589 Pterocodon,[[206]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.
Definition.—Theopilida (vel Tricyrtida triradiata aperta) with three solid free lateral wings on the thorax, and numerous solid terminal feet around the mouth of the abdomen.