Dimensions.—Length of the shell 0.09 (with spines 0.25), breadth 0.15.
Habitat.—South Pacific, Station 300, depth 1375 fathoms.
2. Tympanidium spinosum, n. sp.
Shell with twelve gates; the four lateral gates simple. Basal and mitral gates of about equal size. Shell similar to that of the preceding species, differing mainly in the different armature; the numerous spines, covering the convex outside of the four vertical rings, are not leaf-shaped, but conical, short, of very variable size, partly simple, partly irregularly branched.
Dimensions.—Length of the shell 0.08 (with spines 0.2), breadth 0.12.
Habitat.—South Pacific, Station 295, depth 1500 fathoms.
Subgenus 2. Tympanomma, Haeckel.
Definition.—Shell with sixteen gates (eight median gates, paired on both sides of the sagittal ring, and eight lateral gates, paired on both sides of the frontal ring). The four lateral gates of the two preceding species (subgenus Tympanura) are bisected in Tympanomma by the lateral parts of an incomplete equatorial ring.
3. Tympanidium binoctonum, n. sp. (Pl. [94], fig. 18).
Shell with sixteen gates; the four lateral gates double, bisected by the lateral parts of an incomplete equatorial ring. Basal gates nearly rectangular, of the same breadth as the pentagonal mitral gates, but twice as long. Equatorial outline of the shell (seen in fig. 18 from the apical pole) octagonal. All rods of the shell thin, smooth.