Sagittal ring elliptical, tuberculate. Basal ring trapezoidal, also with roundish thick rods and small irregular tubercles on the margin. Jugular gates ovate, two-thirds as broad as the triangular cardinal gates.
Dimensions.—Height of the sagittal ring 0.08, breadth 0.05.
Habitat.—North Pacific, Station 253, depth 3125 fathoms.
4. Semantrum mülleri, Haeckel.
Stephanolithis mülleri, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi pp. 499, 539, Taf. xxxii. figs. 8a, 8b, 8c.
Sagittal ring nearly semicircular or obliquely ovate, thorny. Basal ring also nearly semicircular, with two slight sagittal incisions (one anterior and one posterior), on the lateral edges with numerous small thorns. Jugular pores (pair I of Bütschli) pear-shaped. Cardinal pores (pair II of Bütschli) triangular. Sometimes (but not constantly) a pair of cervical bows connects the scapular bars with the subvertical dorsal rod of the sagittal ring.
Dimensions.—Height of the sagittal ring 0.09, breadth 0.06.
Habitat.—Fossil in Barbados.
5. Semantrum sphragisma, n. sp.
Sagittal ring circular, smooth. Basal ring also nearly circular and smooth; its four basal gates of nearly equal size, elliptical or subcircular; the jugular pores scarcely smaller than the cardinal pores. All rods smooth, cylindrical, without edges and thorns.