Page:Scientific results HMS Challenger vol 18 part 1.djvu/645

Rh Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the spines 0.05, basal breadth 0.04.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Distriactis corallantha, n. sp.

Disk thorny, three times as broad as the medullary shell, with regular, circular pores, about eight on the radius. Six marginal spines of equal size and equidistant, conical, nearly as long as the diameter of the disk, half as broad at the base as the medullary shell.

Dimensions.—Diameter of the disk 0.12, of the medullary shell 0.04; length of the spines 0.1, breadth 0.02.

Habitat.—South Pacific, Station 300, surface.

3. Distriactis alterna, n. sp.

Disk smooth, five times as broad as the medullary shell, about twelve pores on the radius. Six marginal spines pyramidal, at equal distances, but unequal alternating size; three larger (perradial) spines as long as the shell radius, three smaller between them (interradial) half as long and broad.

Dimensions.—Diameter of the disk 0.15, of the medullary shell 0.03; length of the three major spines 0.08, of the three minor 0.05.

Habitat.—North Atlantic, Station 353, surface.

4. Distriactis palmantha, n. sp.

Disk rough, four times as broad as the medullary shell, about ten pores on the radius. Six marginal spines conical, at equal distances, but unequal alternating size; three larger (perradial) spines as long as the shell diameter, three smaller between them (interradial) as long as the radius.

Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the three major spines 0.2, of the three minor 0.1,

Habitat.—South Atlantic, Station 325, surface.

5. Distriactis amphithecta, n. sp.

Disk thorny, three times as broad as the medullary shell. Six marginal spines conical, of very different size; one single (anterior) much larger than the five others, the opposite (posterior) much smaller. The other four spines are paired, the anterior pair larger than the posterior.

Dimensions.—Diameter of the disk 0.15, of the medullary shell 0.05; length of the longest spine 0.2, of the shortest 0.04, of the anterior pair 0.1, of the posterior 0.07.

Habitat.—Indian Ocean, Cocos Islands, surface, Rabbe.