Habitat.—Fossil in Barbados.
9. Pterocorys apis, Haeckel.
Pterocodon apis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 82, Taf. xix. fig. 3.
Shell slender, smooth, with two distinct strictures. Length of the three joints = 1 : 2 : 6, breadth = 2 : 3 : 4. Cephalis hemispherical, with a curved, conical horn of three times the length. Thorax very small, with three nearly horizontal, conical wings, which are slightly curved downwards, and twice as long as the thorax. Abdomen cylindrical, three times as long as the thorax, with wide, truncate mouth. Pores small, subregular, circular. Differs from all other species in the very small size of the thorax; the abdomen is broken off in Ehrenberg's figure.
Dimensions.—Length of the three joints, a 0.15, b 0.02, c 0.06; breadth, a 0.02, b 0.03, c 0.04.
Habitat.—Cosmopolitan; Atlantic, Pacific, many stations; also fossil in Barbados.
10. Pterocorys melitta, Haeckel.
Rhopalocanium ornatum, Bury, 1862, Polycystins of Barbados, Taf. vi. fig. 4.
Shell slender, smooth, with two deep strictures. Length of the three joints = 1 : 1 : 3, breadth = 1 : 2 : 2. Cephalis subspherical, with a pyramidal horn of twice the length. Thorax broad and short, loaf-shaped, with three conical wings, which are horizontally expanded, and half as long as the shell. Abdomen cylindrical, with wide, truncate mouth. Pores small, subregular, circular.
Dimensions.—Length of the three joints, a 0.025, b 0.03, c 0.09; breadth, a 0.03, b 0.06, c 0.06.