Spines straight, cylindrical, trifid, with one pair of lateral branches. The nine diverging, straight, and smooth branches are connected in the distal part by slender concave bows, so that the whole skeleton exhibits nine wide meshes, three larger pentagonal and six smaller triangular.
Dimensions.—Length of the spines 0.14, of their branches 0.07.
Habitat.—North Atlantic, west coast of Norway (Claparède), surface.
3. Plectophora novena, n. sp.
Spines slightly curved, three-sided prismatic, thorny, with two pairs of lateral branches. The six smaller distal branches end freely, whilst the six larger basal branches are connected by slender convex bows. There are therefore nine wide meshes, as in the preceding closely allied species.
Dimensions.—Length of the spines 0.18, of the basal branches 0.08.
Habitat.—North Atlantic, Færöe Channel (Gulf Stream) (John Murray), surface.
4. Plectophora pyramidalis, n. sp.
Spines straight, three-sided prismatic, with three to four verticils of short lateral branches. The branches of the basal verticils are again ramified, and form by connecting bows a delicate loose framework, covering the three sides of a flat pyramid, the three edges of which are the three radial spines.
Dimensions.—Length of the spines 0.2, base of the pyramid 0.16.