2. Pteropilium hoplites, n. sp.
Shell in the general form and in the irregular, quadrangular fenestration similar to the preceding species, but more heavy and with different proportions. Length of the three joints = 1 : 6 : 4, breadth = 2 : 6 : 8. Cephalis twice as broad as in Pteropilium stratiotes. Thorax more slender and subovate. Abdomen truncate, conical, gradually dilated, with straight, non-geniculate outline. Network coarser, with larger square meshes and thicker bars.
Dimensions.—Length of the three joints, a 0.03, b 0.12, c 0.08; breadth, a 0.05, b 0.12, c 0.16.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
3. Pteropilium eques, n. sp.
Shell in the general form and in the irregular, quadrangular fenestration similar to those of the two preceding species, but more slender and with different proportions. Length of the three joints = 1 : 3 : 2, breadth = 2 : 4 : 4. Cephalis flatter. Thorax subconical, also flatter. Abdomen short, cylindrical, with straight outline. Network looser than in the two preceding species, with larger square meshes and thinner bars.
Dimensions.—Length of the three joints, a 0.03, b 0.08, c 0.06; breadth a 0.06, b 0.12, c 0.12.
Habitat.—Central Pacific, Station 274, depth 2750 fathoms.
Subgenus 2. Arachnopilium, Haeckel, 1881, Prodromus, p. 435.
Definition.—Thorax with three large lateral holes between the three latticed wings.
4. Pteropilium clathrocanium, n. sp. (Pl. 64, fig. 7).
Shell very delicate, with two deep strictures. Length of the three joints = 2 : 4 : 2, breadth = 2 : 10 : 5. Cephalis subspherical, with circular, polygonally-framed pores, and a central, three-sided pyramidal, apical horn of twice the length. Thorax three-sided pyramidal, with three large, ovate holes between three prominent latticed wings. From its surface arises a very delicate, arachnoidal network with irregular, polygonal meshes, enveloping also the entire cephalis. Abdomen wide and short, as long as the cephalis, and half as broad as the distance of the wings, twice as broad as the constricted mouth.
Dimensions.—Length of the three joints, a 0.04, b 0.08, c 0.04; breadth, a 0.05, b 0.2, c 0.1.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
