Page:Scientific results HMS Challenger vol 18 part 2.djvu/292

1168 2. Archiphormis campanulata, n. sp.

Shell campanulate, with nine prominent denticulate ribs, prolonged into nine terminal feet, which are broad, lamellar, truncate, nearly vertical, one-third as long as the shell. Pores between the ribs circular, disposed in nine longitudinal and seven to eight transverse rows.

Dimensions.—Shell 0.09 long, 0.1 broad; mouth 0.06 broad.

Habitat.—Central Pacific, Station 270, depth 2925 fathoms.

3. Archiphormis urceolata, n. sp. (Pl. 98, fig. 11).

Shell urceolate, with nine smooth prominent curved ribs, prolonged into nine triangular convergent short feet, scarcely one-sixth as long as the shell. Pores between the ribs in nine regular longitudinal rows, twice or three times as broad as long, quadrangular, eight to twelve pores in each row. Mouth constricted, half as broad as the shell.

Dimensions.—Shell 0.13 long, 0.11 broad; mouth 0.06 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

Definition.— (vel Monocyrtida multiradiata aperta) without radial ribs in the wall of the campanulate or ovate shell. Mouth with a coronet of radial feet. Apex with a horn.

The genus Halicalyptra and the two following closely allied genera differ from the preceding Archiphormida in the absence of radial ribs. The multiradiate structure is indicated only by the terminal spines or feet, forming a coronet around the mouth. These feet are either the free ends of reduced ribs, or new productions of the peristome. Halicalyptra may be derived from Calpophæna and Petalospyris by loss of the basal lattice-plate of the cephalis. But it is also possible that it has been derived from Anthocyrtis by loss of the cephalis, and that its shell corresponds to the thorax of the latter.

Definition.—Shell smooth, without spines or thorns (other than the feet and the apical horn).