slender neck from the inflated, subspherical thorax. Abdomen cylindrical, with a wide open, truncate mouth. Pores subregular, hexagonal, of equal size, four to six times as broad as the thin, thread-like bars.
Dimensions.—Length of the three joints, a 0.02, b 0.08, c 0.07; breadth, a 0.02, b 0.09, c 0.08.
Habitat.—Tropical Pacific, many Stations (200, 224, 271, &c.), surface, and in various depths.
2. Theocyrtis barbadensis, Haeckel.
Shell thin-walled, smooth. Length of the three joints = 2 : 4 : 5, breadth, 2 : 5 : 4. Cephalis ovate or conical, with a strong, conical horn, without external stricture, dilated into the campanulate thorax. Abdomen cylindrical, with a wide open, truncate mouth. Pores subregular, circular, quincuncially disposed, of about the same breadth as the bars.
Dimensions.—Length of the three joints, a 0.04, b 0.08, c 0.1; breadth, a 0.04, b 0.1, c 0.08.
Habitat.—Fossil in the Tertiary rocks of Barbados.
3. Theocyrtis cylindrica, Haeckel.
Shell elongate, cylindrical, straight, smooth. Length of the three joints = 1 : 2 : 6, breadth = 1 : 3 : 3. Cephalis hemispherical, with a thick, pyramidal horn of the same length (the edges of the horn giving to it the appearance of being composed of two converging spines). Thorax truncated, conical. Abdomen perfectly cylindrical, much elongated. Pores subregular, circular, twice as broad as the bars, quincuncially disposed. Mouth wide open, truncate.
Dimensions.—Length of the three joints, a 0.02, b 0.04, c 0.12; breadth, a 0.03, b 0.06, c 0.06.
Habitat.—Tropical Pacific, Station 266, depth 2750 fathoms; fossil in Barbados.
4. Theocyrtis elegans, Haeckel.
Shell slender, cylindrical, straight, smooth. Length of the three joints = 1 : 2 : 7, breadth = 1 : 3 : 3. Cephalis subconical, with a small conical horn. Thorax campanulate, conical. Abdomen cylindrical, very slender. Pores subregular, circular, small, disposed in transverse rows, three in the thorax, six to eight in the abdomen. Mouth wide open, truncate.
Dimensions.—Length of the three joints, a 0.01, b 0.02, c 0.07; breadth, a 0.015, b 0.03, c 0.03.
Habitat.—Fossil in Barbados and Sicily.
