Dimensions.—Diameter of the shell 0.13; length of the six marginal spines 0.12, basal breadth 0.04.
Habitat.—Tropical Atlantic, Station 348, surface.
2. Hexonaspis hexapleura, n. sp. (Pl. [140], fig. 15).
All six hydrotomical spines of nearly equal size, triangular, compressed, six-edged, about as long as the radius of the shell and twice as long as broad on the base. Two strong prominent ribs on each flat side of the spines. Shell very thick-walled, with a very small cavity.
Dimensions.—Diameter of the shell 0.11; length of the six marginal spines 0.06, basal breadth 0.03.
Habitat.—South Atlantic, Station 332, surface.
3. Hexonaspis hexagona, n. sp.
All six hydrotomical spines of equal size, very short, triangular, only half as long as broad at the base. The whole shell accordingly forms a regular hexagon, the six corners of which are formed by the distal points of the rudimentary spines, the six sides by their straight lateral edges. Shell very dark.
Dimensions.—Diameter of the shell 0.2; length of the six marginal spines 0.03, basal breadth 0.06.
Habitat.—South Atlantic (east of Patagonia), Station 318, surface.