3. Acanthonia denticulata, n. sp.
Spines quadrangular prismatic, with prominent elegantly denticulated edges, of equal breadth throughout their whole length. Both ends pyramidal, without leaf-cross. (Similar to Amphilonche denticulata, but with the twenty spines all equal, and with spherical central capsule.)
Dimensions.—Length of the spines 0.12 to 0.16, breadth 0.008.
Habitat.—Central Pacific, Stations 266 to 274, surface.
4. Acanthonia mülleri, Haeckel.
Spines quadrangular, nearly prismatic, but tapering gradually from the pyramidal base towards the distal bifid apex, which bears two thin, parallel, or little divergent teeth; four edges elegantly denticulated; base without leaf-cross. Central capsule yellowish or reddish.
Dimensions.—Length of the spines 0.12 to 0.18, basal breadth 0.005.
Habitat.—Mediterranean (Messina); Atlantic, Stations 348 to 352, surface.
5. Acanthonia fragilis, Haeckel.
Spines quadrangular, nearly prismatic, but gradually thickened from the pyramidal base towards the distal truncated end; four edges regularly denticulated; base without leaf-cross. Central capsule opaque.
Dimensions.—Length of the spines 0.5 and more, basal breadth 0.002 to 0.003, distal breadth 0.008 to 0.016 or more.
Habitat.—Mediterranean (Messina); North Atlantic, Station 354, surface.
6. Acanthonia convexa, n. sp.
Spines quadrangular, with four broad lamellar, convex, prominent edges, which from the broader middle part are thinned towards the two emarginated ends; each end with a small quadrangular pyramid, without leaf-cross. All the twenty spines of this species exhibit nearly the same form, which is seen in the caudal or posterior (geotomical) spine of Amphilonche anomala (Monogr. d. Radiol., Taf. xviii. fig. 23, b).
Dimensions.—Length of the spines 0.12 to 0.16, breadth in the middle part 0.02 to 0.025.
Habitat.—North Pacific, Station 244, surface.
7. Acanthonia concava, n. sp.
Spines quadrangular, with four broad lamellar, concave, prominent edges, which from the smaller middle part are broadened towards the two emarginated ends; each end with a small
