Habitat.—Fossil in Barbados.
11. Theoconus ariadnes, n. sp.
Shell conical, nearly bell-shaped, smooth. Length of the three joints = 1 : 2 : 3, breadth = 1 : 3 : 5. Cephalis subspherical, with a conical spine of about the same length. Thorax hemispherical, thin-walled. Abdomen conical, slightly constricted at the wide open mouth. Pores regular, circular, twice as large in the thick-walled abdomen as in the thin-walled thorax.
Dimensions.—Length of the three joints, a 0.018 to 0.022, b 0.03 to 0.035, c 0.06 to 0.07; breadth, a 0.015 to 0.02, b 0.04 to 0.06, c 0.07 to 0.09.
Habitat.—Cosmopolitan; Atlantic, Indian, and Pacific Oceans, common, surface.
12. Theoconus dionysius, Haeckel.
Thyrsocyrtis dionysia, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xii. fig. 5.
Thyrsocyrtis jacchia, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xii. fig. 7.
Shell bell-shaped, smooth. Length of the three joints = 1 : 3 : 5, breadth = 1 : 4 : 5. Cephalis subspherical, with a conical, irregularly denticulate horn of twice or thrice the length. Thorax inflated, nearly spherical, truncate at both poles, separated by a deep stricture from the cephalis, as well as from the conical abdomen, which is dilated gradually towards the wide mouth. Pores in the thorax subregular, circular, in the abdomen twice to four times larger, and irregular.
Dimensions.—Length of the three joints, a 0.02, b 0.06, c 0.1; breadth, a 0.02, b 0.08, c 0.1.