Genus 333. Pristacantha,[[373]] n. gen.
Definition.—Astrolonchida with numerous simple apophyses (eight to sixteen or more on each radial spine) which are arranged in four longitudinal rows opposite in pairs in the form of a cross.
The genus Pristacantha differs from all other Stauracanthida in the multiplication of the crossed apophyses (at least eight on each spine), and exhibits therefore to them the same relation as Astrolonche exhibits to the other Phractacanthida. The remarkable Astrolonchidium serratum appears intermediate between both groups.
1. Pristacantha octodon, n. sp. (Pl. [130], fig. 9).
Spines four-sided prismatic, a little broader in the middle part than at either end, with thin prominent edges. Apex truncate or pyramidal. Base pyramidal, with a small leaf-cross. From the four edges arise in the basal half (between first and second third of the length) eight slender, conical, or triangular apophyses (two on each edge).
Dimensions.—Length of the spines 0.4 to 0.6, breadth 0.02 to 0.04.
Habitat.—Central Pacific, Station 271, surface.
2. Pristacantha dodecodon, n. sp. (Pl. [130], fig. 8).
Spines four-winged, of lanceolate outline, tapering from the broader middle towards the two ends. Apex pyramidal. Base with a large leaf-cross. From the four wings arise in the basal part (between first and second third of the length) twelve triangular apophyses (three from each wing).
Dimensions.—Length of the spines 0.3, breadth in the middle 0.03.