Page:Scientific results HMS Challenger vol 18 part 2.djvu/210

1086 straight, much longer than the thorax, divergent, and at the broader base irregularly fenestrated, without three larger holes.

Dimensions.—Cephalis 0.05 long, 0.08 broad; thorax 0.07 long, 0.12 broad.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

3. Acrospyris pyramidalis, n. sp.

Shell three-sided pyramidal, with slight collar stricture. Cephalis campanulate, with deep sagittal stricture and stout ring, armed with a strong pyramidal horn of the same length. Thorax shorter and broader, truncate. Pores irregular, roundish, scarce. Three feet divergent, three-sided pyramidal, as long as the cephalis.

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.02 long, 0.08 broad.

Habitat.—Fossil in Barbados.

4. Acrospyris macrocephala, n. sp.

Shell spinulate, with deep sagittal and very deep collar stricture. Cephalis very large, nut-shaped, twice as long and broad as the small, truncate, pyramidal thorax. Pores irregular, roundish. Horn spindle-shaped, nearly as long as the cephalis; the three divergent feet are of the same form and size as the horn, and arise as three ribs from the deep collar stricture.

Dimensions.—Cephalis 0.1 long, 0.15 broad; thorax 0.05 long, 0.09 broad.

Habitat.—Fossil in Barbados.

5. Acrospyris fragilis, n. sp.

Shell very thin-walled and fragile, with deep sagittal and collar strictures. Pores very small and numerous, circular. Cephalis nut-shaped, nearly spherical, with a slender bristle-shaped horn of the same length. Basal stricture with two large collar pores only (luminella). Thorax nearly three-sided prismatic, longer than the cephalis, with three parallel ribs, prolonged into three slender, long, bristle-shaped feet.

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.08 long, 0.06 broad.

Habitat.—North Pacific, Station 244, surface.

Definition.— with three basal feet, without apical horn.

The genus Phormospyris has been derived from Acrospyris, its ancestral form, by reduction and loss of the apical horn; it therefore bears to the latter the same relation that Tristylospyris has to the ancestral Tripospyris.