Chapter XI: Literature and History (9)

Shell thick walled, covered with numerous bristle-shaped radial spines (one-third to one-half as long as the six main spines, arising from the lattice-knots). Pores regular, circular, enclosed by prominent, hexagonal frames, four to six times as broad as the bars; seven to eight on the radius. {174}Six main spines triangular pyramidal, with spirally contorted prominent edges, as long as the radius, as broad at the base as one pore.

_Dimensions._--Diameter of the shell 0.13, pores 0.01, bars 0.002; length of the spines 0.06 to 0.8, basal breadth 0.01.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.

12. _Hexastylus cochleatus_, n. sp. (Pl. 21, fig. 1).

Shell thick walled, covered with numerous short, conical spines (about as large as one pore). Pores regular, circular, three times as broad as the bars; eight to nine on the radius. Six main spines triangular pyramidal, with prominent, spirally-twisted edges, as long as the diameter of the shell, and twice as broad at the base as one pore.

_Dimensions._--Diameter of the shell 0.17, pores 0.015, bars 0.005; length of the spines 0.16, breadth 0.03.

_Habitat._--Mediterranean, Corfu, Haeckel, surface.

13. _Hexastylus setosus_, Haeckel.

_Acanthosphæra setosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 285, Taf. ix. fig. 11.

Shell thin walled, covered with numerous short, bristle-shaped spines (not larger than one pore). Pores regular, circular, four times as broad as the bars; thirteen to sixteen on the radius. Six main spines three-sided pyramidal, scarcely one-third as long as the radius. (In the figure of Ehrenberg, _loc. cit._, only four spines are in regular, crossed disposition, two others opposite in oblique direction; this is either an individual abnormality, or an error of drawing; the same species occurs with six spines exactly regularly disposed in the three dimensive axes.)

_Dimensions._--Diameter of the shell 0.15; pores 0.008, bars 0.002; length of the spines 0.02 to 0.03, basal breadth 0.005.

_Habitat._--Indian Ocean, Zanzibar, Pullen; Madagascar, Rabbe.

14. _Hexastylus chilonis_, n. sp.

Shell thin walled, covered with numerous bristle-shaped spines (as long as the radius). Pores regular, circular, twice as broad as the bars; eight to nine on the radius. Six main spines triangular pyramidal, with straight edges, as long as the diameter of the shell, as broad as two pores.

_Dimensions._--Diameter of the shell 0.2, pores 0.02, bars 0.01; length of the spines 0.2, basal breadth 0.05.

_Habitat._--South Atlantic, Station 325, surface.

15. _Hexastylus cleobuli_, n. sp.

Shell thick walled, covered with numerous short, conical spines (twice as large as one pore). Pores regular, circular, of the same breadth as the bars; twelve to thirteen on the radius. Six main spines conical, as long as the radius, three times as broad as one pore.

{175}_Dimensions._--Diameter of the shell 0.24, pores and bars 0.005; length of the spines 0.12, basal breadth 0.016.

_Habitat._--South Pacific, Station 300, depth 1375 fathoms.

Subgenus 3. _Hexastylissus_, Haeckel.

_Definition._--Pores irregular, of unequal size or form; surface of the spherical shell smooth, without radial by-spines (other than the six main spines).

16. _Hexastylus triaxonius_, n. sp. (Pl. 21, fig. 2).

Shell thin walled, with smooth surface. Pores irregular, polygonal, three to six times as broad as the bars; four to six on the radius. Six spines triangular pyramidal, as long as the diameter of the shell, as broad at the base as one pore.

_Dimensions._--Diameter of the shell 0.05, pores 0.004 to 0.008, bars 0.0015; length of the spines 0.04, basal breadth 0.006.

_Habitat._--North Pacific, Station 253, depth 3125 fathoms.

17. _Hexastylus dimensivus_, n. sp. (Pl. 21, fig. 6).

Shell thin walled, with smooth surface. Pores irregular, polygonal, four to eight times as broad as the bars; eleven to thirteen on the radius. Six spines hexagonal pyramidal, as long as the radius, about three times as broad at the base as one pore.

_Dimensions._--Diameter of the shell 0.13, pores 0.006 to 0.009, bars 0.0012; length of the spines 0.06, basal breadth 0.025.

_Habitat._--North Pacific, Station 256, depth 2950 fathoms.

18. _Hexastylus brevispinus_, n. sp.

Shell thin walled, with smooth surface. Pores irregular, roundish, two to four times as broad as the bars; six to eight on the radius. Six spines triangular pyramidal, half as long as the radius, twice as broad as one pore.

_Dimensions._--Diameter of the shell 0.2, pores 0.008 to 0.016, bars 0.004; length of the spines 0.05, basal breadth 0.025.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

19. _Hexastylus longispinus_, n. sp.

Shell thick walled, smooth. Pores irregular, roundish, two to three times as broad as the bars; three to four on the radius. Six spines triangular prismatical, two to three times as long as the diameter of the shell.

{176}_Dimensions._--Diameter of the shell 0.08, pores 0.008 to 0.012, bars 0.004; length of the spines 0.2, breadth 0.01.

_Habitat._--North Atlantic, Station 353, surface.

20. _Hexastylus marginatus_, n. sp. (Pl. 21, fig. 10).

Shell thick walled, rough. Pores irregular, roundish, somewhat funnel-shaped double-edged, two to three times as broad as the bars; twelve to fourteen on the radius. Six spines three-sided pyramidal, somewhat longer than the radius, three times as broad as one pore.

_Dimensions._--Diameter of the shell 0.15, pores 0.007 to 0.01, bars 0.004; length of the spines 0.1, basal breadth 0.025.

_Habitat._--South Pacific, Station 295, depth 1500 fathoms.

21. _Hexastylus conifer_, n. sp.

Shell thick walled, rough. Pores irregular, roundish, scarcely broader than the bars; fifteen to sixteen on the radius. Six spines conical, as long as the radius, five to seven times as broad as one pore.

_Dimensions._--Diameter of the shell 0.18, pores and bars 0.004 to 0.006; length of the spines 0.1, basal breadth 0.03.

_Habitat._--Indian Ocean, Sunda Strait, Rabbe, surface.

Subgenus 4. _Hexastylurus_, Haeckel.

_Definition._--Pores irregular, of unequal size or form; surface of the spherical shell spiny, covered with numerous conical or bristle-shaped by-spines.

22. _Hexastylus dictyotus_, n. sp. (Pl. 21, figs. 8, 9).

Shell thin walled, spiny; short spines conical, smaller than the pore-breadth. Pores irregular, polygonal, five to seven times as broad as the bars; four to six on the radius. Six spines triangular pyramidal, longer than the radius, about as broad as one smaller pore.

_Dimensions._--Diameter of the shell 0.09, pores 0.01 to 0.015, bars 0.002; length of the spines 0.06, basal breadth 0.01.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

23. _Hexastylus hirsutus_, n. sp.

Shell thin walled, densely covered with bristle-shaped, radial spines, half as long as the six main spines. Pores irregular, polygonal, three to four times as broad as the bars; eight to ten on the radius. Six spines triangular pyramidal, as long as the radius, twice as broad as one pore.

{177}_Dimensions._--Diameter of the shell 0.14, pores 0.005 to 0.008, bars 0.002; length of the spines 0.06, basal breadth 0.01.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.

24. _Hexastylus contortus_, n. sp. (Pl. 21, fig. 12).

Shell thick walled, covered with bristle-shaped, radial spines, half as long as the radius. Pores irregular, roundish, two to three times as broad as the bars; seven to eight on the radius. Six spines triangular prismatic, in the distal half spirally twisted like a cork-screw (fig. 12); longer than the diameter of the shell, about as broad as one pore.

_Dimensions._--Diameter of the shell 0.12, pores 0.006 to 0.008, bars 0.003; length of the spines 0.15, breadth 0.015.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

25. _Hexastylus spiralis_, n. sp. (Pl. 21, fig. 7).

Shell thick walled, covered with short conical spines. Pores irregular, roundish, two to three times as broad as the bars; five to six on the radius. Six spines triangular prismatic, with three thin, spirally contorted edges, two to three times as long as the diameter of the shell, about as broad as one large pore.

_Dimensions._--Diameter of the shell 0.16, pores 0.01 to 0.02, bars 0.006; length of the spines 0.3 to 0.5, basal breadth 0.02.

_Habitat._--Tropical Western Pacific, Station 225, depth 4475 fathoms.

Genus 73. _Hexastylarium_,[102] n. gen.

_Definition._--#Cubosphærida# with one simple lattice-sphere and six simple spines of different sizes; one opposite pair larger than the other two.

The genus _Hexastylarium_ differs from its probable ancestral form, _Hexastylus_, by the unequal growth of the six simple spines; two opposite spines of one pair being more strongly developed than the four others, which are equal. They correspond therefore to the three axes of a quadratic crystal.

1. _Hexastylarium heteraxonium_, n. sp.

Cortical shell thin walled, smooth, with regular, hexagonal pores, three times as broad as the bars; eight to ten on the radius. Six spines three-sided pyramidal, at the base as broad as one pore. Two opposite major spines longer than the shell diameter; four others scarcely as long as {178}the radius. (Similar to _Hexastylus phænaxonius_, Pl. 21, fig. 3, but differing in the unequal length of the spines.)

_Dimensions._--Diameter of the shell 0.15, pores 0.12, bars 0.004; length of the two major spines 0.2, of the four minor 0.07.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

2. _Hexastylarium quadratum_, n. sp.

Shell very delicate, with smooth surface, and irregular, polygonal pores, separated by very thin bars. The form of the shell is not, as commonly, a sphere, but a geometrical square octahedron, one axis (with two opposite major spines) being nearly twice as long as the other two dimensive axes; four spines, opposite by pairs in the latter, are only half as long. The eight sides of the octahedral shell are even, equilateral-triangular. Spines angular, thin.

_Dimensions._--Diameter of the shell in the major axis 0.18, in the minor 0.1; length of the major spines 0.24, minor 0.12.

_Habitat._--South Pacific, Station 295, depth 1500 fathoms.

3. _Hexastylarium elongatum_, n. sp.

Shell thick walled, with spiny surface, and with irregular, roundish pores, two to four times as broad as the bars; eight to ten on the radius. Two opposite major spines, three to four times as long as the shell diameter, whilst the four other spines are very short, scarcely as long as the radius. All six spines at the base three-sided pyramidal, the two longer being cylindrical.

_Dimensions._--Diameter of the shell 0.1; length of the major spines 0.3 to 0.4, of the minor 0.04, basal breadth 0.02.

_Habitat._--North Pacific, Station 244, surface.

Genus 74. _Hexastylidium_,[103] Haeckel, 1881, Prodromus, p. 450.

_Definition._--#Cubosphærida# with one simple lattice-sphere and six simple spines in pairs different; the two opposite spines of each pair equal, the three pairs unequal.

The genus _Hexastylidium_ differs from its probable ancestral form, _Hexastylus_, by the unequal growth of the six simple spines; the two spines of each pair reaching the same dimensions, whilst the three pairs are different. They correspond therefore to the three axes of a rhombic crystal.

1. _Hexastylidium rhomboides_, n. sp.

Shell thin walled, smooth, with irregular, polygonal pores and very thin bars. Its form is not, as commonly, a sphere, but a rhombic octahedron. The radial proportion of the three unequal {179}dimensive axes = 1 : 2 : 4. The radial proportion of the three pairs of spines = 1 : 3 : 8. Spines thin cylindrical, at the base angular.

_Dimensions._--Diameter of the major shell axis 0.2, middle 0.1, minor 0.05; length of the major spines 0.3, middle 0.12, minor 0.04.

_Habitat._--Indian Ocean, Madagascar, Rabbe, surface.

2. _Hexastylidium spirale_, n. sp.

Shell thick walled, spherical, thorny, with irregular, roundish pores, three to five times as broad as the bars; six spines very stout, prismatic (as broad as one large pore), with three ring-like, spirally convoluted edges. Two opposite major spines of extraordinary length, ten to twelve times as long as the shell diameter, the two middle opposite spines being about as long as the latter, the two minor scarcely one-third as long. (Similar to _Hexastylus spiralis_, Pl. 21, fig. 7, but distinguished by the very unequal length of the spines.)

_Dimensions._--Diameter of the shell 0.12; length of the major spines 1 to 1.5 mm., middle 0.15, minor 0.04.

_Habitat._--Central Pacific, Station 266, surface.

Subfamily HEXALONCHIDA,[104] Haeckel, 1881, Prodromus, pp. 449, 451.

_Definition._--#Cubosphærida# with two concentric spherical lattice-shells.

Genus 75. _Hexalonche_,[105] Haeckel, 1881, Prodromus, p. 451.

_Definition._--#Cubosphærida# with two concentric lattice-spheres and six simple spines of equal size.

The genus _Hexalonche_ is the most simple form, and probably the common ancestral form, of all Hexalonchida, or those Cubosphærida which possess two concentric latticed spheres, connected by six radial beams. Commonly one shell is intracapsular (medullary shell) and the other extracapsular (cortical shell); but sometimes also both shells are extracapsular, and these forms may perhaps be better separated as a peculiar genus _Hexadilemma_. In _Hexalonche_ all six simple spines are of equal size, and opposite by pairs in three equal dimensive axes, corresponding to the three equal axes of a tesseral crystal. It can be derived from _Hexastylus_ by duplication of the lattice-shell.

Subgenus 1. _Hexalonchara_, Haeckel.

_Definition._--Pores of the cortical shell regular or subregular, of nearly equal size and similar form; surface smooth, without radial by-spines (other than the six main spines).

{180}1. _Hexalonche phænaxonia_, n. sp.

Cortical shell thin walled, smooth; its pores regular, hexagonal, six to eight times as broad as the bars; eight to ten to twelve on the radius. Medullary shell one-third as broad, with regular, hexagonal pores of half size. Six spines triangular pyramidal, as long as the radius of the shell, at the base as broad as one pore. (Differs from _Hexastylus phænaxonius_, Pl. 21, fig. 3, only in the medullary shell and the six inner radial beams, connecting it with the cortical shell.)

_Dimensions._--Diameter of the outer shell 0.15, pores 0.01 to 0.015, bars 0.015 to 0.02; inner shell 0.05; length of the spines 0.08, basal breadth 0.01.

_Habitat._--Central Pacific, Stations 266 to 271, depth 2425 to 2925 fathoms.

2. _Hexalonche rosetta_, n. sp. (Pl. 25, figs. 3, 3_a_, 3_b_).

Cortical shell thick walled, smooth, two and a half time as broad as the medullary shell. Pores of the latter (fig. 3_a_) regular circular; eight to ten on the half meridian, about as broad as the bars between them. Pores of the outer shell regular, hexagonal, remarkable for a very peculiar form and arrangement. In the transverse section of the shell (fig. 3_b_) they appear as narrow, hexagonal prismatic canals, twice as high as broad, and four to five times as broad as the thin elevated bars between them. Every seven meshes form together a larger, regular hexagon (six pores surrounding one central pore). The periphery of these larger, rosette-like hexagons projects more strongly from the surface than the walls between the smaller hexagons. On the half meridian of the shell may be counted six to seven larger and eighteen to twenty smaller hexagons. The six radial beams between the two shells are thin, three-sided prismatic, not broader than the bars of the network, the prominent prolongations of which form six very strong spines of peculiar club-like shape (fig. 3), as long as the radius of the outer shell. The three wings of the club are lower in the inner, higher in the outer half; the broadest part of the spine (at the base and in the outer third) is as broad as a hexagonal rosette (equal to three meshes of the outer shell); its outer apex is pyramidal.

_Dimensions._--Diameter of the outer shell 0.13, pores 0.008 to 0.01, bars 0.02; inner shell 0.05; length of the spines 0.07, distal breadth 0.03.

_Habitat._--Tropical West Pacific, Station 225, depth 4475 fathoms.

3. _Hexalonche favosa_, n. sp.

Cortical shell thick walled, smooth, four times as broad as the medullary shell. Pores of the former regular circular, hexagonally framed, deep funnel-shaped, of the same breadth as the bars; six to eight on the radius. Six spines triangular-pyramidal, as long as the radius, at the base twice as broad as one pore. (Differs from the similar _Hexastylus favosus_ mainly in the possession of a medullary shell.)

_Dimensions._--Diameter of the outer shell 0.16, pores and bars 0.012; inner shell 0.04; length of the spines 0.08, basal breadth 0.025.

_Habitat._--Equatorial Atlantic, Station 348, depth 2450 fathoms; also fossil in Barbados.

{181}4. _Hexalonche octahedra_, n. sp. (Pl. 22, figs. 8, 8_a_).

Cortical shell a regular octahedron, thin walled, with twelve more or less rounded edges (between the bases of the spines), and with smooth surface, three times as broad as the spherical medullary shell. Pores of the former regular circular (three times as large as those of the latter), four times as broad as the bars; five to seven on the radius. Six spines three-sided prismatic, with thickened base and cuspidated end, somewhat longer than the radius, and once to twice as broad as one pore.

_Dimensions._--Diameter of the outer shell 0.11, pores 0.01, bars 0.0025; inner shell 0.04; length of the spines 0.08, bars 0.01.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

5. _Hexalonche conicornis_, n. sp. (Pl. 22, fig. 2).

Cortical shell thick walled, smooth, three times as broad as the medullary shell. Pores of both spheres regular circular, three to four times as broad as the bars; those of the thick walled outer shell six to seven on the radius, twice as large as those of the thin walled inner shell; six radial beams between the two spheres, very thin, cylindrical; six spines short, conical, scarcely as long as the radius of the outer shell, at the base twice as broad as one pore.

_Dimensions._--Diameter of the outer shell 0.12 to 0.14, pores 0.01, bars 0.003; inner shell 0.04 to 0.05; length of the spines 0.04 to 0.06, basal breadth 0.02.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

6. _Hexalonche curvicornis_, n. sp. (Pl. 25, fig. 4).

Cortical shell thick walled, smooth, not much larger than the medullary shell (= 4 : 3). Pores of both spheres regular circular, nearly of the same size, three times as broad as the bars between them; seven to nine on the radius. Six spines three-sided prismatic, inside and outside of the exterior shell of equal thickness, twice as broad as one pore, longer than the diameter of the outer shell, and in a singular manner curved like an ox horn; the three edges of each horn somewhat spirally twisted.

_Dimensions._--Diameter of the outer shell 0.16, pores 0.01, bars 0.003; inner shell 0.12; length of the spines 0.2, breadth 0.02.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.

7. _Hexalonche brevicornis_, n. sp.

Cortical shell thin walled, smooth, three times as broad as the medullary shell. Pores of the former regular circular, double-edged, six to eight times as broad as the thin bars, five to six on the radius. Six spines triangular pyramidal, as broad as one pore and only twice as long.

_Dimensions._--Diameter of the outer shell 0.14, pores 0.02, bars 0.003; inner shell 0.045; length of the spines 0.05, basal breadth 0.02.

_Habitat._--North Pacific, Station 253, depth 3125 fathoms.

{182}8. _Hexalonche grandis_, n. sp.

Cortical shell thick walled, smooth, four times as broad as the medullary shell. Pores of the outer shell regular circular, four times as broad as the bars; thirteen to fifteen on the radius. Six spines conical, scarcely half as long as the radius, at the base as broad as one pore.

_Dimensions._--Diameter of the outer shell 0.2 to 0.32, pores 0.01 to 0.02, bars 0.003 to 0.005; inner shell 0.06 to 0.08; length of the spines 0.06, breadth 0.02.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

Subgenus 2. _Hexalonchetta_, Haeckel.

_Definition._--Pores of the cortical shell regular or subregular, of nearly equal size and similar form; surface covered with numerous conical or bristle-shaped radial by-spines.

9. _Hexalonche amphisiphon_, n. sp. (Pl. 25, figs. 2, 2_a_, 2_b_).

Cortical shell thin walled, armed with very numerous bristle-shaped, radial by-spines, a quarter to a half as long as the six main spines. Pores regular hexagonal, twelve to fourteen on the radius, with very thin bars, prolonged on the outer as well as the inner surface into a short truncated conical tube (Pl. 25, fig. 2_b_). Medullary shell octahedral, with irregular polygonal meshes and very thin bars between them (fig. 2_a_), connected with the outer (six to eight times larger) shell by six very thin radial beams. These are prolonged outside into six strong pyramidal spines, nearly as long as the diameter of the outer shell, with sharp straight edges, at the base twice as broad as one pore.

_Dimensions._--Diameter of the outer shell 0.15, pores 0.01, bars 0.001; inner shell 0.02; length of the spines 0.12, basal breadth 0.02.

_Habitat._--Central Pacific, Station 271, surface.

10. _Hexalonche anaximandri_, n. sp. (Pl. 22, fig. 5).

Cortical shell thin walled, covered with short conical spines (smaller than the pores), three times as broad as the medullary shell. Pores of the outer shell subregular hexagonal, four times as broad as the bars; five to seven on the radius. Inner shell with regular hexagonal pores of half the size, connected with the outer by six strong, three-sided prismatic beams, which are prolonged outside into six very stout pyramidal spines, with three prominent edges, longer than the radius and twice as broad as one pore.

_Dimensions._--Diameter of the outer shell 0.12, pores 0.01, bars 0.0025; inner shell 0.04; length of the spines 0.07, basal breadth 0.02.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

{183}11. _Hexalonche octocolpa_, n. sp. (Pl. 22, figs. 6, 6_a_).

Cortical shell thin walled, nearly octahedral, with eight hemispherical or bosom-shaped vaultings, corresponding to the eight faces of a regular octahedron, the three axes of which are indicated by the six spines. Surface covered with short bristle-shaped spines. Pores regular hexagonal, ten to fifteen times as broad as the thin bars; seven to nine on the radius. Medullary shell (fig. 6_a_) spherical, with regular circular pores, one-third as broad as the cortical shell, and connected with it by six strong triangular radial beams, which are prolonged outside into pyramidal spines, one-third as long as the shell diameter.

_Dimensions._--Diameter of the outer shell 0.2, pores 0.03, bars 0.002; inner shell 0.06; length of the spines 0.06, breadth 0.02.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.

12. _Hexalonche cristata_, n. sp.

Cortical shell thick walled, four times as broad as the medullary shell, and covered with short conical spines arising from the nodal points of elevated crests which form regular hexagonal frames around the funnel-shaped circular pores. These are two to three times as broad as the crested bars; eight to ten on the radius. Six spines three-sided pyramidal, with strong prominent edges, about as long as the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.16 to 0.2, pores 0.01 to 0.015, bars 0.003 to 0.005; inner shell 0.04 to 0.05; length of the spines 0.08 to 0.12, basal breadth 0.01 to 0.03.

_Habitat._--Central Pacific, Station 266 to 274, depth 2350 to 2925 fathoms.

13. _Hexalonche serrata_, n. sp.

Cortical shell thick walled, four times as broad as the medullary shell, with spiny surface. Pores regular circular, twice as broad as the bars, five to seven on the radius, funnel-shaped, separated by hexagonal frames, the sharp crests of which are serrated; at the nodal-points longer bristle-shaped by-spines. Six main spines triangular prismatic, longer than the diameter of the shell, twice as broad as one pore.

_Dimensions._--Diameter of the outer shell 0.15, pores 0.01, bars 0.005; inner shell 0.04; length of the spines 0.2, breadth 0.02.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

14. _Hexalonche anaximenis_, n. sp. (Pl. 25, fig. 5).

Cortical shell thin walled, twice as broad as the medullary shell, and covered with short conical by-spines. Pores regular circular, twice as broad as the bars; five to six on the radius. Circular pores of the medullary shell one-third as broad. Radial main spines conical, nearly as long as the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.1, pores 0.01, bars 0.005; inner shell 0.05; length of the spines 0.04, basal breadth 0.015.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

{184}15. _Hexalonche aspera_, n. sp.

Cortical shell thin walled, three times as broad as the medullary shell, and covered with short conical spines. Pores regular circular, four to six times as broad as the bars; eight to ten on the radius. Radial spines conical, about as long as the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.12, pores 0.08, bars 0.0015; inner shell 0.04; length of the spines 0.1, basal breadth 0.02.

_Habitat._--South Pacific, Station 300, depth 1375 fathoms.

16. _Hexalonche castanella_, n. sp.

Cortical shell thick walled, five times as broad as the medullary shell, and covered with numerous short conical spines. Pores regular circular, twice as broad as the bars; ten to twelve on the radius. Radial spines triangular pyramidal, about as long as the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.22, pores 0.01, bars 0.005; inner shell 0.045; length of the spines 0.12, basal breadth 0.02.

_Habitat._--North Atlantic, Station 353, depth 3125 fathoms.

Subgenus 3. _Hexalonchilla_, Haeckel.

_Definition._--Pores of the cortical shell irregular, of unequal size or form; surface smooth, without radial by-spines (other than the six main spines).

17. _Hexalonche hexacantha_, Haeckel.

_Haliomma hexacanthum_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 35, Taf. iv. fig. 5.

_Haliomma hexacanthum_, Haeckel, 1862, Monogr. d. Radiol., p. 430.

Cortical shell thin walled, smooth, with irregular polygonal pores (commonly hexagonal or pentagonal), two to three times as broad as the bars; eight to ten on the radius. Medullary shell one quarter as broad, connected with the former by six thin radial beams which are prolonged outside into six triangular pyramidal spines (not quadrangular, as Müller describes), longer than the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.2, pores 0.01 to 0.015, bars 0.005; inner shell 0.05; length of the spines 0.15, basal breadth 0.015.

_Habitat._--Mediterranean (Messina, Nice, Genoa).

18. _Hexalonche geometrica_, n. sp.

Cortical shell thick walled, smooth, with very peculiar geometrical formation of its network, the pores of which are of very different size and form, but highly regular disposition. Each of the six {185}triangular spines is surrounded at the base by three small roundish pores (between the three wings of its base), and further by a coronal of six very large pores, three of which are pentagonal, and the other three (alternating) heptagonal. The six basal coronals are separated by irregular smaller pores. Medullary shell thin walled, with regular hexagonal pores (three on the radius) and thin bars, connected with the outer shell by six thin triangular prismatic radial beams, which are prolonged outside into short pyramidal spines (half as long as the radius).

_Dimensions._--Diameter of the outer shell 0.2, thirty-six larger pores of the coronals 0.03 to 0.04, smaller pores between them 0.01 to 0.02, bars 0.005; inner shell 0.05 (with pores of 0.008); length of the spines 0.05, basal breadth 0.03.

_Habitat._--South Atlantic, off Buenos Ayres, Station 323, depth 1900 fathoms.

19. _Hexalonche pythagoræa_, n. sp. (Pl. 22, fig. 1).

Cortical shell thick walled, smooth, three times as broad as the medullary shell. Pores irregular roundish, twice to eight times as broad as the bars, of very different size; usually in the space between every three spines are three or six larger pores, separated by numerous smaller pores (often the disposition of the larger pores is much more regular than in the figured specimen). Medullary shell with regular circular pores, connected with the outer by six very thin radial beams, which are prolonged outside into six short triangular pyramidal spines about as long and broad as the half radius.

_Dimensions._--Diameter of the outer shell 0.12, pores 0.008 to 0.03, bars 0.004; inner shell 0.04; length of the spines 0.04, basal breadth 0.03.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.

20. _Hexalonche aristarchi_, n. sp. (Pl. 22, fig. 3).

Cortical shell thin walled, smooth, four times as broad as the medullary shell. Pores irregular polygonal, of very variable size and form, twice to six times as broad as the bars; six to ten on the radius. Medullary shell with regular hexagonal pores, connected with the outer by six very thin radial beams, which are prolonged outside into six triangular pyramidal spines, nearly as long as the radius.

_Dimensions._--Diameter of the outer shell 0.1, pores 0.005 to 0.02, bars 0.003; inner shell 0.025; length of the spines 0.05, basal breadth 0.01.

_Habitat._--North Pacific, Station 241, depth 2300 fathoms.

21. _Hexalonche ekphantæa_, n. sp.

Cortical shell thin walled, smooth, four times as broad as the medullary shell. Pores irregular roundish, of very variable size and form, twice to six times as broad as the bars, ten to fifteen on the radius. Six spines cylindro-conical, longer than the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.2, pores 0.004 to 0.012, bars 0.002; inner shell 0.05; length of the spine 0.3, basal breadth 0.01.

_Habitat._--Indian Ocean, Sunda Strait, surface, Rabbe.

{186}Subgenus 4. _Hexalonchusa_, Haeckel.

_Definition._--Pores of the cortical shell irregular, of different size or form; surface covered with numerous conical or bristle-shaped, radial by-spines.

22. _Hexalonche philosophica_, n. sp. (Pl. 22, fig. 4).

Cortical shell thin walled, covered with short conical spines, three times as broad as the medullary shell. Pores irregular polygonal, or more roundish, twice to six times as broad as the bars; six to eight on the radius. Inner shell of the same structure, pores three times smaller, connected with the outer by six very thin radial beams, which are prolonged outside into six strong, triangular pyramidal spines, as long as the radius. (Similar to _Hexalonche anaximandri_, Pl. 22, fig. 5, but different in the irregular network and the shorter by-spines.)

_Dimensions._--Diameter of the outer shell 0.11, pores 0.005 to 0.015, bars 0.0025; inner shell 0.04; length of the spines 0.06, breadth 0.02.

_Habitat._--North Atlantic, Færöe Channel, John Murray; Iceland, Krabbe, surface.

23. _Hexalonche seleuci_, n. sp.

Cortical shell thick walled, covered with numerous short, bristle-shaped spines. Pores of very different size and form, and of a peculiar, subregular disposition, similar to those of _Hexalonche geometrica_ (though in this case more regular). Each of the six triangular main spines (which reach nearly the length of the radius) is surrounded at the base by three small roundish pores, and these are further supplemented by a coronal of six very large polygonal pores; the six coronals are separated by irregular rows of smaller pores. Inner shell equal to one-third of the outer. Six main spines pyramidal, as long as the radius.

_Dimensions._--Diameter of the outer shell 0.16, larger pores 0.03 to 0.04, smaller pores 0.01 to 0.02, bars 0.05 to 0.01; inner shell 0.05; length of the spines 0.08, basal breadth 0.03.

_Habitat._--North Atlantic, Station 354, surface.

24. _Hexalonche sexaculeata_, Haeckel.

_Haliomma sexaculeatum_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 87, Taf.
i. fig. 8.

Cortical shell thick walled, twice as broad as the medullary shell, and covered with short conical spines. Pores irregular polygonal (mostly hexagonal), twice to three times as broad as the bars; six to eight on the radius. Six spines triangular-pyramidal (not quadrangular), somewhat longer than the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.11, pores 0.06 to 0.08, bars 0.03; inner shell 0.06; length of the spines 0.07, basal breadth 0.015.

_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Caltanisetta.

{187}25. _Hexalonche heracliti_, n. sp. (Pl. 22, fig. 7).

Cortical shell thick walled, covered with bunches of small spines, each bunch at the nodule point between every three pores composed of four to eight conical spinules. Pores irregular roundish, twice to four times as broad as the bars; four to six on the radius. Inner shell equal to one-third of the outer, connected with it by six thin radial beams, which are prolonged outside into six strong triangular spines about as long as the radius.

_Dimensions._--Diameter of the outer shell 0.15, pores 0.015 to 0.03, bars 0.08; inner shell 0.05; length of the spines 0.06, basal breadth 0.02.

_Habitat._--Indian Ocean, Madagascar, Rabbe, surface.

26. _Hexalonche xenophanis_, n. sp.

Cortical shell thin walled, covered with numerous short conical spines, four times as broad as the medullary shell. Pores irregular circular, twice to eight times as broad as the bars; five to seven on the radius. Six spines conical or more cylindrical, as long as the diameter of the shell or longer.

_Dimensions._--Diameter of the outer shell 0.16 to 0.24, pores 0.01 to 0.04, bars 0.005; inner shell 0.04 to 0.06; length of the spines 0.2 to 0.3, breadth 0.02.

_Habitat._--Central Pacific, Stations 266 to 272, surface.

27. _Hexalonche setosa_, n. sp.

Cortical shell thin walled, covered with numerous bristle-shaped spines, half as long as the six main spines. Pores irregular roundish, twice to five times as broad as the bars; ten to twelve on the radius. Inner shell equal to one-fifth of the outer. Six spines conical, as long as the radius.

_Dimensions._--Diameter of the outer shell 0.25, pores 0.008 to 0.02, bars 0.004; inner shell 0.05; length of the spines 0.12, basal breadth 0.03.

_Habitat._--South Pacific, Station 291, surface.

28. _Hexalonche hystricina_, n. sp. (Pl. 25, fig. 6).

Cortical shell thick walled, covered with numerous bristle-shaped spines, half as long as the six main spines. Pores irregular roundish, twice to four times as broad as the bars; five to seven on the radius. Medullary shell with very small circular pores, one-fourth of the cortical shell, connected with it by six thin prismatic radial beams, which are prolonged outside into six strong, short, three-sided pyramidal, cuspidated spines, only half as long as the radius of the outer shell.

_Dimensions._--Diameter of the outer shell 0.2, pores 0.015 to 0.03, bars 0.008; inner shell 0.05; length of the spines 0.05, basal breadth 0.02.

_Habitat._--Indian Ocean, Sunda Strait, surface, Rabbe.

{188}Genus 76. _Hexancistra_,[106] Haeckel, 1881, Prodromus, p. 451.

_Definition._--#Cubosphærida# with two concentric lattice-spheres and six branched spines of equal size.

The genus _Hexancistra_ differs from its ancestral form, _Hexalonche_, in the ramification of the six radial spines. These are very different in the two subgenera; in _Hexancora_ each spine bears only three simple lateral branches, while in _Hexapitys_ there are three rows of verticillate lateral branches on each spine.

Subgenus 1. _Hexancora_, Haeckel.

_Definition._--Each radial spine with three simple lateral branches only (one branch from each edge of the triangular spine).

1. _Hexancistra tricuspis_, n. sp. (Pl. 22, fig. 9).

Cortical shell thin walled, covered with short conical by-spines, three times as broad as the medullary shell; its pores regular circular, three times as broad as the bars; ten to twelve on the radius. Pores of the medullary shell half as large, also regular circular. The two shells connected by six thin prismatic radial beams, which are prolonged outside into six very stout main spines, three-sided prismatic, as long as the shell diameter, with three thin wing-like edges. Each edge at the distal end prolonged into a strong curved lateral branch.

_Dimensions._--Diameter of the outer shell 0.13, inner 0.4; cortical pores 0.01, bars 0.003; medullary pores 0.005, bars 0.003; length of the six spines 0.13, breadth 0.02.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.

2. _Hexancistra ancorata_, n. sp.

Cortical shell thick walled, smooth, twice as broad as the medullary shell; its pores regular circular, twice as broad as the bars; six to eight on the radius. Six radial spines, three-sided prismatic, as long as the shell radius, with three recurved lateral branches at the distal end like the three teeth of an anchor.

_Dimensions._--Diameter of the outer shell 0.1, inner 0.05; cortical pores 0.006, bars 0.003; length of the six spines 0.05, breadth 0.02.

_Habitat._--South Pacific, Station 296, depth 1825 fathoms.

3. _Hexancistra triserrata_, n. sp. (Pl. 22, fig. 10).

Cortical shell thin walled, thorny, twice to three times as broad as the medullary shell; the two shells connected by six strong triangular beams. Inner shell spherical, with very small, regular, circular {189}pores; ten to twelve on the half meridian. Bars as broad as the pores. Outer shell regularly octahedral, with eight triangular perfectly regular even faces, separated by eight prominent edges; the meshes circular, regular, about twelve to fourteen on the half meridian, two to three times as broad as the bars between them. Six strong radial spines, about as long as the diameter of the outer shell, three-sided prismatic, cuspidate; their three edges prominent, serrate, spirally twisted. Each spine bears about its middle three strong flattened lateral branches, nearly perpendicular to it, not serrated, and slightly curved.

_Dimensions._--Diameter of the outer shell 0.13, inner 0.045; pores of the former 0.01, of the latter 0.004; length of the spine 0.12, breadth 0.014.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.

4. _Hexancistra quadricuspis_, n. sp. (Pl. 22, fig. 11).

Cortical shell thin walled, covered with short bristle-shaped by-spines, three and a half times as broad as the medullary shell. Pores of the latter regular circular, small; pores of the former three to six times as large, very irregular, roundish, double-edged. Six radial spines, three-sided prismatic, about as long as the shell diameter, with three wing-like, slightly twisted edges, which are prolonged towards the distal end into three curved horn-shaped branches.

_Dimensions._--Diameter of the outer shell 0.17, inner 0.05; cortical pores 0.01 to 0.03, bars 0.005; medullary pores 0.003, bars 0.001; length of the spines 0.15, breadth 0.013.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.

Subgenus 2. _Hexapitys_, Haeckel, 1881, Prodromus, p. 451.

_Definition._--Each radial spine with three rows of verticillate lateral branches (a row arising from each edge of the spine).

5. _Hexancistra mirabilis_, n. sp. (Pl. 23, fig. 3).

_Hexapitys mirabilis_, Haeckel, 1881, Prodromus, p. 451.

Cortical shell very thin walled, three times as broad as the medullary shell. Inner shell spherical, with very delicate, subregular hexagonal meshes; seven to eight on the half diameter. Outer shell octahedral, with irregular polygonal meshes of very different size; on the surface numerous thin accessory radial spines, equal in length to its radius. Six main spines, extremely long and stout, many times longer than the diameter of the outer shell, nearly as broad as the radius of the inner shell, three-sided prismatic, with sharp, prominent, spirally twisted edges; on every edge a great number of thin lateral branches, arranged perpendicularly to it, as long as the diameter of the outer shell, and pinnated by ten to twenty pairs of delicate secondary spinules, biserial and perpendicular to the primary branches. (In the figured specimen the spherical central capsule, between both shells, was well preserved; its nucleus nearly filled the medullary shell. The thick jelly-veil around it was radially striped and octahedral.)

{190}_Dimensions._--Diameter of the outer shell 0.13, of the inner 0.05; length of the spines 0.5 to 0.8 or more, breadth 0.02.

_Habitat._--Central Pacific, Station 271, surface.

Genus 77. _Hexaloncharium_,[107] n. gen.

_Definition._--#Cubosphærida# with two concentric lattice-spheres and six simple spines of different sizes; one opposite pair larger than the two others.

The genus _Hexaloncharium_ exhibits the same relation to its ancestral form, _Hexalonche_, that _Hexastylarium_ bears to _Hexastylus_. Two opposite spines of one pair are larger than the four others, and correspond to the three axes of a quadratic crystal.

1. _Hexaloncharium octahedrum_, n. sp.

Cortical shell smooth, three to four times as broad as the spherical medullary shell, each having regular circular pores, twice to three times as broad as the bars. Form of the outer shell not a sphere, but a regular octahedron, with eight congruent, equilateral triangular even faces. Two opposite spines twice as long as the shell diameter, whilst the four others are scarcely equal to it. Basal breadth of all six the same (three times as large as one pore); form, three-sided prismatic, with cuspidate distal end. (Similar to _Hexalonche octahedra_, Pl. 22, fig. 8, but distinct in the unequal length of the spines.)

_Dimensions._--Diameter of the outer shell 0.16, inner 0.045; length of the major spine 0.3, minor 0.12, basal breadth 0.03.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

2. _Hexaloncharium philosophicum_, n. sp.

Cortical shell spherical, covered with short conical by-spines, twice as broad as the medullary shell; both with regular circular pores three to four times as broad as the bars. Two major spines cylindrical, with conical apex, three times as long as the four others, which are conical and about as long as the shell radius; basal breadth of all six the same (equal to one pore). Similar to _Hexalonche anaximenis_ (Pl. 25, fig. 5), but distinct in the enormous prolongation of two opposite spines.

_Dimensions._--Diameter of the outer shell 0.12, inner 0.06; length of the two major spines 0.2, of the four minor 0.06, basal breadth 0.02.

_Habitat._--Central Pacific, Station 267, depth 2700 fathoms.

{191}3. _Hexaloncharium hystricinum_, n. sp.

Cortical shell spherical, three times as broad as the medullary shell, and densely covered with oblique bristle-shaped by-spines. Pores irregular roundish. Two opposite major spines three-sided prismatic, longer than the shell diameter; four minor spines pyramidal, scarcely half as long as the shell radius. (Somewhat similar to _Hexalonche hystricina_, but distinct in the prolongation of two major spines.)

_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; length of the two major spines 0.2, four minor 0.03, basal breadth 0.02.

_Habitat._--South Pacific, Station 288, surface.

Genus 78. _Hexalonchidium_,[108] Haeckel, 1881, Prodromus, p. 451.

_Definition._--#Cubosphærida# with two concentric lattice-spheres and six simple spines of different sizes in pairs; the two opposite spines of each pair equal, the three pairs unequal.

The genus _Hexalonchidium_ exhibits the same relation to _Hexalonche_ that _Hexastylidium_ bears to _Hexastylus_; the growth of the three spine-pairs is different, whilst both spines of each pair are equal; they correspond therefore to the three axes of a rhombic crystal.

1. _Hexalonchidium axonometrum_, n. sp.

Cortical shell thin walled, covered with short bristle-shaped by-spines, twice as broad as the medullary shell; both with regular hexagonal meshes, twice to three times as broad as the bars (inner meshes half as broad as the outer). All three spine-pairs three-sided prismatic, of very different length but of equal breadth (equal to three pores). Major spine-pair twice as long as the shell diameter; middle pair about equal to the latter, minor scarcely half as long. (Similar to _Hexalonche anaximandri_, Pl. 22, fig. 5, but distinct in the different length of the spines.)

_Dimensions._--Diameter of the outer shell 0.12, inner 0.06; length of the major spines 0.25, middle 0.1, minor 0.04.

_Habitat._--Indian Ocean, Madagascar, surface, Rabbe.

Subfamily HEXACONTIDA,[109] Haeckel, 1881, Prodromus, pp. 449, 452.

_Definition._--#Cubosphærida# with three concentric, spherical, or octahedral lattice-shells.

{192}Genus 79. _Hexacontium_, Haeckel,[110] 1881, Prodromus, p. 452.

_Definition._--Shell with three concentric lattice-spheres and six simple spines of equal size.

The genus _Hexacontium_, the ancestral form of the Hexacontida, is probably derived from _Hexalonche_ by duplication of the medullary shell. As in the latter, all six spines are of equal size, opposite in pairs in the three dimensive axes, and correspond therefore to the three equal axes of a tesseral crystal.

Subgenus 1. _Hexacontanna_, Haeckel.

_Definition._--Pores of the cortical shell regular or subregular, of nearly equal size and similar form; surface smooth, without radial spines or papillæ (other than the six main spines).

1. _Hexacontium phænaxonium_, n. sp.

Cortical shell thin walled, smooth; its pores regular hexagonal, six to nine times as broad as the bars; twelve to sixteen on the radius. Radial proportion of the three spheres = 1 : 2 : 4. Both medullary shells of the same structure as the cortical shell, only with smaller pores. The three spheres connected by six thin radial beams, which are prolonged on the outside into six strong triangular pyramidal spines, as long as the radius of the cortical shell, and, at the base, as broad as one of its pores. (Differs from _Hexastylus phænaxonius_ and from _Hexalonche phænaxonia_, Pl. 21, fig. 3, in the larger size and the triple shell.)

_Dimensions._--Diameter of the outer sphere 0.2, middle 0.1, inner 0.05; cortical pores 0.008, bars 0.0012; length of the spines 0.1.

_Habitat._--Central Pacific, Station 270, surface.

2. _Hexacontium axotrias_, n. sp. (Pl. 24, fig. 3).

Cortical shell thin walled, smooth; its pores regular circular, five to six times as broad as the bars; eleven to thirteen on the radius. Radial proportion of the three spheres = 1 : 3 : 8. Outer medullary shell with hexagonal frames around the regular circular pores (five to six on the radius). Inner medullary shell with simple small circular pores (three on the radius). The two outer shells connected by six triangular prismatic beams, which are prolonged outside to the length of the cortical radius or more.

_Dimensions._--Diameter of the outer sphere 0.2, middle 0.07, inner 0.025; cortical pores 0.016, bars 0.003; length of the spines 0.1 to 0.015, basal breadth 0.02.

_Habitat._--North Pacific, Station 253, surface.

3. _Hexacontium hexactis_, Haeckel.

_Actinomma hexactis_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 91, Taf.
ii. fig. 7.

Cortical shell thick walled, smooth, or a little rough. Pores regular circular, of the same breadth as the bars; five to seven on the radius. Radial proportion of the three spheres {193}= 1 : 3 : 6. Both medullary shells of the same structure, but with smaller pores. Six spines triangular pyramidal, nearly as long as the diameter of the outer shell, three times as broad at the base as one pore.

_Dimensions._--Diameter of the outer sphere 0.1, middle 0.05, inner 0.016; cortical pores and bars 0.008; length of the spines 0.08, basal breadth 0.025.

_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

4. _Hexacontium lævigatum_, n. sp. (Pl. 24, fig. 6).

Cortical shell thick walled, quite smooth. Pores regular circular, with double margins, eight to ten on the radius, of the same breadth as the smooth bars. Radial proportion of the three spheres = 1 : 2 : 6. All three spheres connected by six very thin radial beams, which are prolonged outside into six short, stout, triangular, pyramidal spines, half as long as the radius of the outer shell.

_Dimensions._--Diameter of the outer shell 0.13, middle 0.04, inner 0.02; cortical pores and bars 0.008; length of the spines 0.04, basal breadth 0.02.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

5. _Hexacontium triplosphærium_, n. sp.

Cortical shell thick walled, smooth. Pores regular circular, three times as broad as the bars; ten to twelve on the radius. Radial proportion of the three spheres = 1 : 3 : 10. Six spines conical, about as long as the radius of the cortical shell.

_Dimensions._--Diameter of the outer shell 0.16, middle 0.05, inner 0.016; cortical pores 0.012, bars 0.004; length of the spines 0.07, basal breadth 0.02.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

6. _Hexacontium octahedrum_, n. sp.

Cortical shell a regular octahedron, thin walled, with twelve more or less rounded edges (between the spine-bases) and with smooth surface; its pores regular circular, five to seven on the radius, four times as broad as the bars. Radial proportion of the three shells = 1 : 3 : 9. Both medullary shells spherical, with very small circular pores. Six inner bars very thin; six outer spines (their prolongations) triangular pyramidal, as long as the radius of the outer shell. (Differs from _Hexalonche octahedra_, Pl. 22, fig. 8, almost solely in the duplication of the medullary shell.)

_Dimensions._--Diameter of the outer shell 0.12, middle 0.04, inner 0.013.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.

7. _Hexacontium circumtextum_, n. sp. (Pl. 25, figs. 7, 7_a_).

Cortical shell double, enclosing a simple medullary shell. Radial proportion of the three spheres = 3 : 10 : 12. Inner cortical shell very thick walled, with regular circular, double-edged pores, four times as broad as the bars; seven to nine on the radius. From each nodal-point between {194}every six pores arises a small, bristle-shaped, radial spine, as long as the diameter of one pore. The distal ends of all these spines are connected by very delicate tangential threads, and consequently form by their attachment an outer cortical shell, with regular hexagonal meshes and smooth surface. Six main spines short, three-sided prismatic, scarcely as long as half the radius of the outer shell.

_Dimensions._--Diameter of the outer shell 0.12, middle 0.1, inner 0.03; pores of the middle shell 0.004, bars 0.001; length of the spines 0.025, basal breadth 0.01.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.

Subgenus 2. _Hexacontella_, Haeckel.

_Definition._--Pores of the cortical shell regular or subregular, of nearly equal size and similar form; surface covered with numerous conical or bristle-shaped, radial spines (other than the six main spines).

8. _Hexacontium hexagonale_, n. sp.

Cortical shell thin walled, bristly, with very delicate network; its pores regular hexagonal, twelve to sixteen on the radius, ten to twelve times as broad as the thin thread-like bars. At each nodal-point of the network (between every three meshes) arises a bristle-shaped, radial spine, as long as the diameter of one mesh. Six main spines hexagonal, as long as the radius of the outer shell, as broad at its base as one mesh. Radial proportion of the three spheres = 1 : 2 : 4. Pores of both medullary shells also regular hexagonal, but much smaller, in the middle shell eleven to twelve, in the inner, six to seven on the half meridian.

_Dimensions._--Diameter of the outer shell 0.12, of the middle 0.06, of the inner 0.03; meshes of the outer shell 0.008; length of the six spines 0.05, basal thickness 0.008.

_Habitat._--Indian Ocean, Ceylon, surface, Haeckel.

9. _Hexacontium favosum_, n. sp. (Pl. 24, figs. 2, 2_a_).

Cortical shell very thick walled, spiny, with regular, honeycomb-like network; its meshes funnel-shaped, with circular inner, hexagonal outer aperture, twice as broad as the bars; five to seven on the radius. Between every three meshes (at each corner of the hexagon) arises a short radial thorn, not so long as the thickness of the shell-wall. Six radial spines very short and stout, three-sided pyramidal, scarcely half so long as the radius of the outer shell. Radial proportion of the three spheres = 1 : 2 : 5. Pores of both medullary shells regular, circular, about as broad as the bars, six to eight on the half meridian.

_Dimensions._--Diameter of the outer shell 0.1 to 0.12, of the middle 0.04 to 0.05, of the inner 0.02; meshes of the outer shell 0.008; length of the six spines 0.2 to 0.3, basal breadth 0.015.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

10. _Hexacontium sceptrum_, n. sp. (Pl. 24, figs. 1, 1_a_).

Cortical shell thick walled, spiny, with regular, honeycomb-like network; its meshes funnel-shaped, with circular inner, hexagonal outer aperture, three to four times as broad as the bars; {195}five to six on the radius. Between every three meshes arises a short radial thorn, as long as the thickness of the shell-wall. Six radial spines sceptre-shaped, six-sided, somewhat constricted towards their middle part, strong, as long as the radius of the outer shell, as broad as one of its meshes. Radial proportion of the three spheres = 1 : 2 : 6. Pores of the two inner shells regular hexagonal, with thin bars, six to eight on the half meridian (fig. 1_a_).

_Dimensions._--Diameter of the outer shell 0.13, of the middle 0.04, of the inner 0.02; pores of the outer shell 0.01, of the middle 0.008, of the inner 0.004; length of the six spines 0.06, basal breadth 0.015.

_Habitat._--Equatorial Atlantic, Station 347, surface.

11. _Hexacontium prionacanthum_, n. sp. (Pl. 24, figs. 7, 7_a_).

Cortical shell thick walled, thorny; its pores regular circular, with elevated hexagonal frames six to nine on the radius, twice as broad as the crest-shaped bars. At each nodal-point of the hexagon arises one short conical papilla or thorn. Radial proportion of the three spheres = 1 : 3 : 10. Pores of both medullary shells much smaller, regular circular. Six main spines three-sided prismatic, longer than the radius of the outer shell, as broad as one of its meshes; their three edges serrated, with ten to twelve teeth.

_Dimensions._--Diameter of the outer shell 0.15, middle 0.045, inner 0.015; cortical pores 0.01, bars 0.005; length of the spines 0.1, breadth 0.012.

_Habitat._--West Tropical Pacific, Station 225, depth 4475 fathoms.

12. _Hexacontium clavigerum_, n. sp. (Pl. 23, fig. 5).

Cortical shell very thick walled, thorny; its pores regular circular, hexagonally framed, three times as broad as the bars, nine to twelve on the radius; between them short conical papillæ or thorns arising at the nodal-points. Radial proportion of the three spheres = 1 : 2 : 5. Outer medullary shell with regular circular, much smaller pores; connected with the cortical shell by numerous (twenty to thirty) thin radial beams. Six main spines very stout, club-shaped, scarcely as long as the radius of the outer shell, three times as broad as one of its pores, three-sided, with three to four teeth on each edge.

_Dimensions._--Diameter of the outer shell 0.2, of the middle 0.08, of the inner 0.04; cortical pores 0.012, bars 0.004; length of the six spines 0.08, breadth 0.03.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

13. _Hexacontium floridum_, n. sp. (Pl. 24, fig. 4).

Cortical shell papillose, thick walled. Pores regular, six-lobed, four times as broad as the bars, five to seven on the radius; each pore with six (sometimes also five or seven) concave indentations or lobules; between the pores at the nodal-points arise short conical papillæ or thorns. Radial proportion of the three spheres = 1 : 2 : 3. Radial main spines pommel-shaped, three-sided prismatic, longer than the radius of the outer shell, two to three times as broad as one pore.

{196}_Dimensions._--Diameter of the outer shell 0.12, middle 0.06, inner 0.03; cortical pores 0.012, bars 0.003; length of the six spines 0.08, breadth 0.03.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.

14. _Hexacontium hexaconicum_, n. sp.

Cortical shell spiny, thick walled. Pores regular circular, of the same breadth as the bars, ten to twelve on the radius; between them long bristle-shaped by-spines, half as long as the six main spines. Radial proportion of the three spheres = 1 : 3 : 9. Six main spines conical, as long as the radius of the outer shell, four times as broad at the base as one pore.

_Dimensions._--Diameter of the outer shell 0.18, middle 0.06, inner 0.02; cortical pores and bars 0.005; length of the spines 0.1, basal breadth 0.02.

_Habitat._--Antarctic Sea, Station 157, depth 1950 fathoms.

15. _Hexacontium asteracanthion_, Haeckel.

_Haliomma asteracanthion_, Haeckel, 1860, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 816.

_Actinomma asteracanthion, Haeckel_, 1862, Monogr. d. Radiol., p. 441,
Taf. xxiii. figs. 5, 6.