Page:Scientific results HMS Challenger vol 18 part 2.djvu/74

950 6. Dendrocircus barbadensis, n. sp.

Gate irregularly ovate or nearly semicircular. Ring of the same oblique form, thick, with interrupted and distorted edges, armed with eight to twelve larger irregularly formed and branched acute spines; between them numerous conical smaller spines. This common species is very polymorphous and variable.

Dimensions.—Diameter of the ring 0.05 to 0.08; length of the spines 0.005 to 0.02.

Habitat.—Fossil in Barbados.

7. Dendrocircus stalactites, n. sp. (Pl. 81, fig. 14).

Gate obliquely ovate. Ring irregularly ovate or roundish, very thick, without edges, armed with numerous (eight to twelve or more) short and stout branches, which are shorter than the diameter of the gate, irregularly disposed and branched, with very numerous clustered blunt ramules.

Dimensions.—Diameter of the gate 0.07 to 0.09; length of the spines 0.02 to 0.06.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Definition.— with typical basal feet (or cortinar feet).

Definition.— with a simple dipleuric or bilateral ring, bearing at the base three divergent feet (one odd caudal and two paired lateral feet).

The genus Cortina and the following Stephanium represent together the small but very important group of Cortinida, differing from the simple Lithocircida in the possession of three typical basal feet, which are transmitted to the majority of the by heredity, and produce their peculiar triradial structure. They appear therefore as a combination of the simple ring (Zygocircus) with three basal feet (Plagonium). One of these three divergent feet is the odd caudal foot, opposite to the apical horn; the two others are the paired lateral or pectoral feet. (On the probable origin and the typical signification of Cortina compare above, pp. 891-894.)

1. Cortina tripus, n. sp. (Pl. 83, fig. 9).

Ring ovate, smooth, or with a few short thorns. Apical horn oblique, curved, simple, smooth, about as long as the sagittal axis of the ring. Feet divergent, curved, simple, smooth, about as