4. Tympaniscus tripodiscus, n. sp. (Pl. 94, fig. 7).
Basal ring of about the same size as the mitral ring, with three large and stout divergent feet (two lateral and one caudal). Sagittal ring stout, broader than the two spiny subsagittal rings; the upper part of the latter bears two ascending arches, which are united with the large apical horn arising from the apex of the sagittal ring. Six columellæ nearly vertical, slightly curved on the outside; their lateral edges armed with numerous simple or forked spines.
Dimensions.—Breadth of the shell 0.1, total length 0.12.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
5. Tympaniscus quadrupes, n. sp. (Pl. 94, fig. 4).
Basal ring larger than the mitral ring, with four short vertical three-sided pyramidal feet of equal size (two lateral and two sagittal); the feet are three-sided pyramidal, with finely denticulate median edges, and bear at the base a horizontal thorny spur. Sagittal ring at the apex with a very large cross-shaped horn, bearing two horizontal thorny lateral branches; the horn is supported by an anterior and a posterior arch. Six columellæ strongly curved and dentate.
Dimensions.—Breadth of the shell 0.15, length 0.12.
Habitat.—South Pacific, Station 298, depth 2225 fathoms.
6. Tympaniscus fibula, Haeckel.
Basal ring of about the same size as the mitral ring, with six large conical descending feet; these are prolongations of the six columellæ, nearly of the same length, slightly divergent, and bear at the base a strong horizontal spur. The six columellæ are strongly curved, spiny, and bear above small arches, which are united with the apical horn of the sagittal ring.
Dimensions.—Breadth of the shell 0.09, height 0.05; total height 0.09.
Habitat.—Fossil in Barbados.
7. Tympaniscus dodecaster, n. sp.
Basal ring of the same size as the mitral ring, with six very large and six alternating smaller, slightly divergent, curved feet, about as long an the shell; the larger are the basal prolongations of the six curved, thorny columellæ. Mitral ring spiny, not overgrown with arches, as in the similar preceding species.
Dimensions.—Length of the shell 0.08, breadth 0.12.
Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.
