Cortical shell thick walled, covered with forty to fifty scattered pyramidal nodules, two and a half times as broad as the medullary shell, connected with it by very numerous thin radial beams. Outer and inner pores irregular roundish or polygonal, two to three times as broad as the bars. (This species in consequence of the cortical nodules may represent a peculiar genus, analogous to Conosphæra, called Anthomma.)

Dimensions.—Diameter of the outer shell 0.13, inner 0.05, inner and outer pores 0.008 to 0.012, bars 0.004.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Genus 20. Liosphæra,^[32] Haeckel, 1881, Prodromus, p. 449.

Definition.—Liosphærida with two cortical (extracapsular) shells (without a medullary or intracapsular shell).

The genus Liosphæra agrees with the preceding Carposphæra in the possession of two concentric latticed spheres; but whilst in the latter genus the inner sphere is a medullary one (intracapsular), the outer a cortical shell (extracapsular), both connected by radial beams piercing the capsule-wall, here in Liosphæra the central capsule lies freely within the inner lattice shell and is not pierced by radial beams. Therefore both shells are here cortical shells, both separated by a distance, which is constantly much smaller than the radius of the inner shell; whereas in Carposphæra this distance is at least as large as that radius (commonly much larger). In Carposphæra the number of pores in both shells is never the same; in several species of Liosphæra this number is the same, each outer regular hexagonal pore exactly corresponding to an inner; the six corners of each connected by six short radial beams.

Subgenus 1. Melitomma, Haeckel.

Definition.—Pores of both shells regular, in each shell all of nearly equal size and form.

1. Liosphæra hexagonia, n. sp. (Pl. 20, fig. 3).

Both shells with the same number of pores, exactly corresponding, about ten on the quadrant. All pores regular, or subregular, hexagonal; the outer twice as broad as the inner. Outer bars very thin, thread-like; inner bars thick, one-third as broad as the pores. Surface smooth. Both shells connected by numerous radial beams, their distance one-third as large as the radius of the inner shell.

Dimensions.—Diameter of the outer shell 0.16, inner 0.12, distance of both 0.02; outer pores 0.014, inner pores 0.007.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

2. Liosphæra rhodococcus, n. sp.

Both shells with the same number of pores, exactly corresponding, about twelve on the quadrant. All pores regular or subregular; the inner circular, with elegant six-lobed frames, twice as broad as the bars; the outer hexagonal, with very thin thread-like bars. All corners of the outer and inner hexagons connected by thin, bristle-shaped radial beams. (Similar to Haliomma rhodococcus, Pl. 19, fig. 6; but with smooth surface and regular hexagonal pores of the outer shell.)

Dimensions.—Diameter of the outer shell 0.2, inner 0.16, distance of both 0.02; outer pores 0.03, inner 0.01.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

3. Liosphæra porulosa, n. sp.

Both shells with regular hexagonal pores; their number in the outer shell seven times as great as in the inner. Pores of the stout inner shell large, three times as broad as the bars, about eight on the quadrant. From each hexagon-corner arises one bristle-shaped radial beam; their distal ends are united by threads (three from each), forming the large meshes of the delicate outer shell. Each of these is divided by very thin threads into seven small circular porules, one central and six around it.

Dimensions.—Diameter of the outer shell 0.25, inner 0.2, distance of both 0.025; outer pores 0.04, their porules 0.012, inner pores 0.15.

Habitat.—Indian Ocean, Sunda Strait, Rabbe; surface.

Subgenus 2. Craspedomma, Haeckel.

Definition.—Pores of both shells irregular, in each shell differing either in form or size.

4. Liosphæra peridromium, n. sp.

Both shells with the same number of large, polygonal, very irregular pores, exactly corresponding (about eight to ten on the quadrant); both with a very delicate thin framework. From the thread-like bars of the inner, very large and thin-walled, sphere arise perpendicularly innumerable short bristles of equal length, which are united at equal distances by tangential thread-like bars, parallel to the former, composing the outer shell. Each mesh is, therefore, surrounded by a delicate ballister or rail.

Dimensions.—Diameter of the outer shell 0.42, inner 0.4, distance of both 0.01; diameter of the meshes 0.02 to 0.06.

Habitat.—North Pacific, Station 250, surface.

5. Liosphæra polypora, n. sp. (Pl. 20, fig. 2).

Both shells with small irregular roundish pores, of about the same size as the bars between them; twenty to thirty on the quadrant. The pores of the outer shell somewhat smaller, therefore much more numerous than the pores of the inner shell. Distance between the two shells about one-third as great as the radius of the inner. Both shells connected by numerous thin radial beams. Surface smooth or a little rough.

Dimensions.—Diameter of the outer shell 0.18, inner 0.14, distance of both 0.02; pores and bars 0.003 to 0.005.

Habitat.—West Tropical Pacific, Station 225, depth 4475.

Subfamily Thecosphærida,^[33] Haeckel, 1881, Prodromus, pp. 449, 452.

Definition.—Liosphærida with three concentric spherical lattice-shells, which are united by radial beams.

Genus 21. Thecosphæra,^[34] Haeckel, 1881, Prodromus, p. 452.

Definition.—Liosphærida with two medullary (intracapsular) shells and one cortical (extracapsular) shell.

The genus Thecosphæra comprises a large number of triple-shelled Sphæroidea, formerly united with Actinomma, but different from this genus in the absence of radial spines. The latticed shell is composed of three concentric spheres, two of which lie within the central capsule (medullary shells), and one outside (cortical shell). This latter is connected with the former by radial beams piercing the wall of the central capsule. From the following Rhodosphæra (with one medullary and two cortical shells) Carposphæra differs also by the distance of the three shells. In the former the distance between the two outer shells is much smaller, in the latter much larger, than the distance between the inner shells.

Subgenus 1. Thecosphærantha, Haeckel.

Definition.—Pores of the cortical shell regular, hexagonal, or circular, with hexagonal frames or lobes, all of nearly equal size and form.

1. Thecosphæra triplodictyon, n. sp.

Cortical shell thin walled, smooth, with regular, hexagonal pores, four times as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 8. Both medullary shells with regular circular pores, twice as broad as the bars, the inner half as broad as the outer. All three shells connected by six thin radial beams, opposite in pairs in the three dimensive axes.

Dimensions.—Diameter of the outer shell 0.2, middle 0.05, inner 0.025; cortical pores 0.012, bars 0.003.

Habitat.—Central Pacific, Station 271, surface.

2. Thecosphæra phænaxonia, n. sp.

Cortical shell thick walled, rough, with regular, circular, hexagonally framed pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 6. Both medullary shells with regular hexagonal pores and thin bars. All three shells connected by six prismatic radial beams, opposite in pairs in the three dimensive axes. (Shell similar to Hexacontium sceptrum, Pl. 24, fig. 1, 1a, but without external spines.)

Dimensions.—Diameter of the outer shell 0.12, middle 0.04, inner 0.02; cortical pores 0.01, bars 0.005.

Habitat.—North Pacific, Station 253, surface.

3. Thecosphæra favosa, n. sp.

Cortical shell thick walled, thorny, with regular, circular, hexagonally framed pores, of the same breadth as the bars. Radial proportion of the three spheres = 1 : 3 : 10. Both medullary shells with regular circular pores, connected with the former by twelve short prismatic, regularly disposed radial beams.

Dimensions.—Diameter of the outer shell 0.2, middle 0.06, inner 0.02; cortical pores and bars 0.008.

Habitat.—Central Pacific, Station 268, surface; also fossil in Barbados.

4. Thecosphæra floribunda, n. sp.

Cortical shell thick walled, smooth, with regular, elegantly six-lobed pores, three times as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 4. Both medullary shells with simple regular circular pores, connected with the former by six dimensive radial beams. (Similar to Hexacontium floridum, Pl. 24, fig. 4, but without external spines.)

Dimensions.—Diameter of the outer shell 0.12, middle 0.06, inner 0.03; cortical pores 0.01, bars 0.0033.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

Subgenus 2. Thecosphærella, Haeckel.

Definition.—Pores of the cortical shell regular, circular, without hexagonal frames or lobes, all of nearly equal size and form.

5. Thecosphæra inermis, Haeckel.

Cortical shell thin walled, rough, with regular circular pores, twice as broad as the bars. Radial proportion of the three spheres and of their circular regular pores = 1 : 2 : 4. All three spheres connected by twelve regularly disposed radial beams.

Dimensions.—Diameter of the outer shell 0.1, middle 0.05, inner 0.025; cortical pores 0.006, bars 0.003.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, at many Stations and at various depths.

6. Thecosphæra æquorea, Haeckel.

Cortical shell thick walled, smooth, with regular circular pores of the same breadth as the bars. Radial proportion of the three spheres and of their regular pores = 1 : 2 : 6 or = 1 : 3 : 9; they are connected by six radial beams, opposite by pairs in the three dimensive axes.

Dimensions.—Diameter of the outer shell 0.08 to 0.12, middle 0.03 to 0.04, inner 0.09 to 0.12; cortical pores and bars about 0.006.

Habitat.—Mediterranean, Corfu, surface; fossil in Greece and Sicily.

7. Thecosphæra medusa, Haeckel.

Cortical shell thick walled, rough or thorny, with regular circular pores of the same breadth as the bars. Radial proportion of the three spheres = 1 : 2 : 4 (or 1 : 2.5 : 6); they are connected by four radial beams, crossed by pairs in two diameters, perpendicular one to another.

Dimensions.—Diameter of the outer shell 0.08 to 0.12, middle 0.04 to 0.06, inner 0.02 to 0.025; cortical pores and bars in average 0.005.

Habitat.—Fossil in Tertiary rocks of Barbados and the Mediterranean.

8. Thecosphæra entactinia, n. sp.

Cortical shell thick walled, smooth, with regular circular pores of the same breadth as the bars. Radial proportion of the three spheres = 1 : 3 : 12; they are connected by very numerous (forty to fifty, or more) thin radial beams.

Dimensions.—Diameter of the outer shell 0.24, middle 0.06, inner 0.02; cortical pores and bars 0.008.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

9. Thecosphæra micropora, n. sp.

Cortical shell thin walled, smooth, with very small and numerous, regular, circular pores, half as broad as the bars. Radial proportion of the three shells = 1 : 2 : 5; they are connected by twenty regularly disposed radial beams.

Dimensions.—Diameter of the outer shell 0.2, middle 0.08, inner 0.04; cortical pores 0.002, bars 0.004.

Habitat.—South Pacific, Station 288, surface.

Subgenus 3. Thecosphærina, Haeckel.

Definition.—Pores of the cortical shell irregular polygonal, of unequal size or dissimilar form.

10. Thecosphæra capillacea, n. sp.

Cortical shell thin walled, smooth, with irregular polygonal pores, three to six times as broad as the bars. Both medullary shells with similar, but smaller, pores. Radial proportion of the three spheres = 1 : 3 : 8; they are connected by very numerous (sixty to eighty or more) thin radial beams. (Similar to Actinomma capillaceum, Pl. 29, fig. 6, but without external spines.)

Dimensions.—Diameter of the outer shell 0.2, middle 0.075, inner 0.025; cortical pores 0.006 to 0.012, bars 0.002.

Habitat.—North Pacific, Station 250, surface.

11. Thecosphæra diplococcus, n. sp.

Cortical shell thick walled, rough, with large irregular polygonal pores, two to three times as broad as the bars. Both medullary shells with small regular circular pores. Radial proportion of the three spheres = 1 : 2 : 6; they are connected by twenty (?) stout radial beams.

Dimensions.—Diameter of the outer shell 0.12, middle 0.04, inner 0.02; cortical pores 0.008 to 0.012, bars 0.004.

Habitat.—South Atlantic, Station 330, surface.

Subgenus 4. Thecosphæromma, Haeckel.

Definition.—Pores of the cortical shell irregular, roundish, of unequal size or dissimilar form.

12. Thecosphæra dodecactis, n. sp.

Cortical shell thin walled, smooth, with large irregular roundish pores, two to eight times as broad as the bars. Both medullary shells with regular circular pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 5; they are connected by twelve regularly disposed stout radial beams.

Dimensions.—Diameter of the outer shell 0.2, middle 0.08, inner 0.04; cortical pores 0.004 to 0.016, bars 0.002.

Habitat.—Central Pacific, Station 263, depth 2650 fathoms.

13. Thecosphæra icosactis, n. sp.

Cortical shell thin walled, with small irregular roundish pores, two to four times as broad as the bars. Both medullary shells with similar but smaller pores. Radial proportion of the three spheres = 1 : 3 : 8; they are connected by twenty thin radial beams.

Dimensions.—Diameter of the outer shell 0.32, middle 0.12, inner 0.04; cortical pores 0.005 to 0.012, bars 0.003.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

14. Thecosphæra maxima, n. sp.

Cortical shell thin walled, with small irregular roundish pores, two to six times as broad as the bars. Both medullary shells with similar, but smaller, pores. Radial proportion of the three spheres = 1 : 3 : 9; they are connected by numerous (forty to sixty or more) thin radial beams.

Dimensions.—Diameter of the outer shell 0.45, middle 0.15, inner 0.05; cortical pores 0.008 to 0.024, bars 0.004.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Genus 22. Rhodosphæra,^[35] Haeckel, 1881, Prodromus, p. 452.

Definition.—Liosphærida with one medullary (intracapsular) shell and two cortical (extracapsular) shells.

The genus Rhodosphæra differs from the preceding Thecosphæra in the same manner in which, among the Dyosphærida, Liosphæra differs from Carposphæra. The cortical shell is double, composed of two not far distant shells, lying outside the central capsule. The distance between the shells is much smaller than the radius of the inner shell. This is connected by radial beams (piercing the central capsule) with the small central medullary shell.

Subgenus 1. Rhodosphærella, Haeckel.

Definition.—Pores of both cortical shells regular, in each shell all of nearly equal size and form.

1. Rhodosphæra hexagonia, n. sp.

Both cortical shells with the same number of regular hexagonal pores; the inner four times as broad as the bars, and half as broad as the outer pores, which are separated by thread-like bars. Medullary shell only one-fourth as broad as the inner cortical shell, with regular hexagonal pores of half the size. (Differs from the similar Liosphæra hexagonia, Pl. 20, fig. 3, by the possession of a medullary shell.)

Dimensions.—Diameter of the outer shell 0.2, middle 0.16, inner 0.04; outer pores 0.013, middle 0.008, inner 0.004.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Rhodosphæra melitomma, n. sp.

Both cortical shells with the same number of regular pores; the inner regular, circular, twice as broad as the bars, with elegant hexagonal frames and six roundish lobes alternating with the six radial spines which arise from the hexagon-corners; these short conical spines are connected at the distal end (at equal distances from the centre) by delicate threads (three from each spine), which form the delicate external shell. Medullary shell one-third as broad as the inner cortical shell, with small, simple, regular circular pores. (If in Carposphæra melitomma, Pl. 20, fig. 4, the distal ends of the spines became united by a cobweb-like outer shell, this species would be formed.)

Dimensions.—Diameter of the outer shell 0.22, middle 0.18, inner 0.06; outer pores 0.025, middle 0.0125, inner 0.005.

Habitat.—Central Pacific, Station 270, depth 2925 fathoms.

Subgenus 2. Rhodosphæromma, Haeckel.

Definition.—Pores of both cortical shells irregular, in each shell of unequal size or dissimilar form.

3. Rhodosphæra palliata, n. sp.

Both cortical shells with an unequal number of irregular roundish pores; the outer pores somewhat smaller and much more numerous than the inner pores; the bars between the latter are thicker. Medullary shell about one quarter as broad as the inner cortical shell, with regular circular pores.

Dimensions.—Diameter of the outer shell 0.4, middle 0.36, inner 0.08; outer pores on an average 0.008, middle 0.012, inner 0.004.

Habitat.—Fossil in Barbados.

4. Rhodosphæra pentaphylla, n. sp.

Both cortical shells with unequal number of irregular roundish pores; the inner pores large, three to four times as broad as the bars; to each inner pore corresponds a group of five smaller outer pores, like the five petals of a flower. Medullary shell half as broad as the inner cortical shell, with regular circular pores.

Dimensions.—Diameter of the outer shell 0.25, middle 0.2, inner 0.1; outer pores on an average 0.006, middle 0.012, inner 0.004.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Subfamily Cromyosphærida,^[36] Haeckel, 1881, Prodromus, pp. 449, 453.

Definition.—Liosphærida with four concentric spherical latticed shells, united by radial beams.

Genus 23. Cromyosphæra,^[37] Haeckel, 1881, Prodromus, p. 453.

Definition.—Liosphærida with two intracapsular (medullary) shells and two extracapsular (cortical) shells; the former united with the latter by radial beams piercing the wall of the central capsule.

The genus Cromyosphæra is the only known genus of Cromyosphærida, or of such Sphæroidea, the smooth shell of which is composed of two medullary and two cortical shells. There may possibly be other Cromyosphærida, in which the shell is composed of one simple medullary and three cortical shells, or only of four extra-capsular cortical shells; but such have not as yet been observed. Caryosphæra polysphærica, Bütschli, 1882 (L. N. 41, Taf. xxiii. fig. 12) is probably a Cromyosphæra (fossil in Barbados).

1. Cromyosphæra quadruplex, n. sp. (Pl. 30, fig. 9).

Radial proportion of the four spheres = 1 : 2 : 4 : 5. Outer cortical shell smooth, with large regular hexagonal pores, ten times as broad as the bars; inner cortical shell with irregular polygonal pores, five times as broad as the bars. Both medullary shells with regular circular pores of the same breadth as the bars.

Dimensions.—Diameter of the four spheres—(A) 0.16, (B) 0.12, (C) 0.06, (D) 0.03.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Cromyosphæra rosetta, n. sp.

Radial proportion of the four spheres = 1 : 2 : 8 : 10. Outer cortical shell smooth, with regular hexagonal pores and very thin bars; inner cortical shell with the same number of exactly corresponding, regular circular, hexagonally framed pores, twice as broad as the bars; the corners of the outer and inner hexagons united by radial bristles. Both medullary shells with regular circular pores, twice as broad as the bars.

Dimensions.—Diameter of the four spheres—(A) 0.2, (B) 0.16, (C) 0.04, (D) 0.02.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

3. Cromyosphæra bigemina, n. sp.

Radial proportion of the four spheres = 1 : 2 : 7 : 8. Outer cortical shell smooth, with regular hexagonal pores and very thin bars; inner cortical shell with the same number of exactly corresponding, regular circular pores. Both medullary shells with regular circular pores of the same breadth as the bars. (Somewhat similar to Hexacromyon elegans, Pl. 24, fig. 9, also with six inner radial beams, but without external radial spines.)

Dimensions.—Diameter of the four spheres—(A) 0.2, (B) 0.17, (C) 0.05, (D) 0.025.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

4. Cromyosphæra cepa, n. sp.

Radial proportion of the four spheres = 1 : 2 : 4 : 5. All four shells of the same structure, thick-walled, with regular circular pores, two to four times as broad as the bars; the size of the pores increases gradually from the inner to the outer shell. Surface thorny. Distance between the second and third shells twice as great as that between the others.

Dimensions.—Diameter of the four spheres—(A) 0.125, (B) 0.1, (C) 0.05, (D) 0.025.

Habitat.—Fossil in Barbados.

5. Cromyosphæra scorodonium, n. sp.

Radial proportion of the four spheres = 1 : 2 : 3 : 4. All four shells of the same structure, thin-walled, with irregular roundish pores, two to four times as broad as the bars; the size of the pores increasing gradually from the inner to the outer shell. Surface smooth. Distance between each two shells equal to the diameter of the innermost.

Dimensions.—Diameter of the four spheres—(A) 0.12, (B) 0.09, (C) 0.06, (D) 0.03.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms; also fossil in Barbados.

6. Cromyosphæra antarctica, n. sp..

Radial proportion of the four spheres = 1 : 2 : 5 : 7. Both cortical shells with irregular polygonal roundish pores; the outermost with thinner bars and rough surface, the inner with thicker bars. Both medullary shells with irregular roundish pores.

Dimensions.—Diameter of the four spheres—(A) 0.18, (B) 0.12, (C) 0.05, (D) 0.025.

Habitat.—Antarctic Ocean; in very large number, together with Rhizosphæra antarctica, in the diatomaceous ooze of Station 157 (3rd March 1874); depth 1950 fathoms.

Subfamily Caryosphærida,^[38] Haeckel, 1881, Prodromus, pp. 449, 454.

Definition.—Liosphærida with numerous (five or more) concentric spherical latticed shells, united by radial beams.

Genus 24. Caryosphæra,^[39] Haeckel, 1881, Prodromus, p. 454.

Definition.—Liosphærida with two intracapsular (medullary) shells and three or more extracapsular (cortical) shells; the former united with the latter by radial beams piercing the wall of the central capsule.

The genus Caryosphæra, the only observed form of this subfamily, comprises those Liosphærida in which the shell is composed of two medullary and three or more cortical shells. Such forms (without radial spines) are very rare; I observed only two species, one with five, the other with six shells. They are derived from Cromyosphæra by further apposition of outer cortical shells.

1. Caryosphæra pentalepas, n. sp.

Shell composed of five concentric spheres, with radial proportion = 1 : 2 : 8 : 10 : 12. Both medullary shells with regular circular pores, twice as broad as the bars. First cortical shell with regular, circular, hexagonally framed pores, three times as broad as the bars; second cortical shell with regular hexagonal pores, four times as broad as the bars; third (outermost) cortical shell with regular hexagonal pores and very thin thread-like bars. Surface smooth.

Dimensions.—Diameter of the five shells—(A) 0.02, (B) 0.04, (C) 0.16, (D) 0.2, (E) 0.24.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

2. Caryosphæra hexalepas, n. sp.

Shell composed of six concentric spheres, with the radial proportion = 1 : 2 : 4 : 5 : 6 : 8. All six shells with regular circular pores, two to four times as broad as the bars, with increasing size from the centrum against the smooth surface.

Dimensions.—Diameter of the six shells—(A) 0.025, (B) 0.05, (C) 0.1, (D) 0.13, (E) 0.16, (F) 0.2.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms; also fossil in Barbados.

Subfamily Plegmosphærida,^[40] Haeckel, 1881, Prodromus, p. 455.

Definition.—Liosphærida with spongy spherical shell, with or without latticed medullary shell in the centre.

Genus 25. Styptosphæra,^[41] Haeckel, 1881, Prodromus, p. 455.

Definition.—Liosphærida forming a solid sphere of spongy framework, without enclosed medullary shell, and without central cavity.

The genus Styptosphæra presents a spherical shell with smooth or rough surface (without radial spines), the whole mass of which is composed of looser or denser spongy wicker-work.

1. Styptosphæra spumacea, n. sp.

Spongy framework of the solid sphere loose, with large polygonal meshes of slightly different size, ten to twenty times as broad as the bars. Structure of the whole spongy sphere the same. Central capsule filled with crystals. Surface smooth.

Dimensions.—Diameter of the sphere 0.32, of the central capsule 0.26, meshes 0.01 to 0.02, bars 0.001.

Habitat.—North Pacific, Station 236, surface.

2. Styptosphæra spongiacea, n. sp.

Spongy framework in the central part of the solid sphere much more compact than in the peripheral part, becoming gradually looser towards the rough surface. Meshes in the centre three to five times, in the periphery fifteen to twenty times as broad as the bent bars.

Dimensions.—Diameter of the sphere 0.45, inner meshes 0.006 to 0.01, outer meshes 0.03 to 0.04, bars 0.002.

Habitat.—Central Pacific, Station 271, surface.

3. Styptosphæra stupacea, n. sp.

Spongy framework of the solid sphere rather compact, everywhere of the same structure, with roundish, nearly equal meshes, six to eight times as broad as the bars. Surface rough with prominent thorns.

Dimensions.—Diameter of the sphere 0.22, meshes 0.01 to 0.012, bars 0.0015.

Habitat.—South Pacific, Station 291, surface.

Genus 26. Plegmosphæra, Haeckel,^[42] 1881, Prodromus, p. 455.

Definition.—Liosphærida forming a hollow sphere of spongy framework, without a medullary shell in the central cavity.

The genus Plegmosphæra develops a large hollow sphere, the wall of which is composed of looser or denser spongy wicker-work. On the inner as well as on the outer face of the spongy shell-wall may be present a simple lattice-sphere from which the threads of the framework arise; but in some species these lattice-plates are quite absent.

Subgenus 1. Plegmosphærantha, Haeckel.

Definition.—Inside and outside of the spongy shell-wall smooth, closed by a lattice-plate with polygonal meshes.

1. Plegmosphæra maxima, n. sp.

Radius of the spherical shell-cavity eight to ten times as great as the thickness of the thin spongy wall. Inside and outside of the wall smooth, closed by a lattice-plate with irregular polygonal meshes. Only three or four meshes in the thickness of the wall.

Dimensions.—Diameter of the spongy sphere 0.8 to 1.0 mm., of its inner cavity 0.7 to 0.8, meshes 0.01 to 0.02, bars 0.002 to 0.003, central capsule 0.5 to 0.6, nucleus 0.1 to 0.15.

Habitat.—Central Pacific, Station 271, surface.

2. Plegmosphæra coelopila, n. sp.

Radius of the spherical shell-cavity eight to ten times as great as the thickness of the spongy wall. Inside and outside of the wall closed by a smooth lattice-plate with irregular polygonal meshes, five to ten times as broad as the bars.

Dimensions.—Diameter of the shell 0.32, of its cavity 0.26, meshes 0.01 to 0.02, bars 0.002.

Habitat.—North Atlantic, Færöe Channel, Gulf Stream, John Murray.

3. Plegmosphæra pachypila, n. sp.

Radius of the spherical shell-cavity about equal to the thickness of the spongy wall. Inside and outside of the wall closed by a smooth lattice-plate with irregular polygonal meshes, three to six times as broad as the bars.

Dimensions.—Diameter of the shell 0.24, of its cavity 0.12.

Habitat.—North Pacific, Station 250, surface.

Subgenus 2. Plegmosphærella, Haeckel.

Definition.—Inside of the spongy shell-wall closed by a smooth lattice-plate, outside rough, spongy, with prominent thorns.

4. Plegmosphæra entodictyon, n. sp.

Radius of the spherical shell-cavity half as great as the thickness of the spongy wall. Inside of the wall closed by a smooth lattice-plate, outside rough, spongy.

Dimensions.—Diameter of the shell 0.24, of its cavity 0.08.

Habitat.—South Pacific, Station 300, surface.

5. Plegmosphæra leptodictyon, n. sp.

Radius of the spongy shell-cavity six times as great as the thickness of the spongy wall. Inside of the wall closed by a smooth lattice-plate, outside rough spongy.

Dimensions.—Diameter of the shell 0.44, of its cavity 0.36.

Habitat.—Central Pacific, Station 266, surface.

Subgenus 3. Plegmosphæromma, Haeckel.

Definition.—Inside of the spongy shell-wall rough spongy, without lattice-plate, outside closed by a smooth lattice-plate.

6. Plegmosphæra exodictyon, n. sp. (Pl. 18, fig. 8).

Radius of the spongy shell-cavity only one-fourth as great as the thickness of the spongy shell-wall. Outside of the wall closed by a smooth lattice-plate, inside rough, spongy.

Dimensions.—Diameter of the shell 0.4, of its cavity 0.08.

Habitat.—South Atlantic, Station 325, surface.

Subgenus 4. Plegmosphærusa, Haeckel.

Definition.—Inside and outside of the spongy shell-wall rough, with spongy or spiny surface, without lattice-plate.

7. Plegmosphæra leptoplegma, n. sp.

Radius of the spherical shell-cavity half as great as the thickness of the loose spongy shell-wall. Inside and outside of the wall rough spongy, not closed by a lattice-plate. Meshes ten to twenty times as broad as the bars.

Dimensions.—Diameter of the shell 0.3, of its cavity 0.088.

Habitat.—North Atlantic, Station 253, surface.

8. Plegmosphæra pachyplegma, n. sp.

Radius of the spherical shell-cavity about equal to the thickness of the dark and dense spongy shell-wall. Inside and outside of the wall rough spongy, not closed by a lattice-plate. Meshes three to five times as broad as the bars.

Dimensions.—Diameter of the shell 0.2, of its cavity 0.1.

Habitat.—Central Pacific, Station 270, surface.

Genus 27. Spongoplegma,^[43] Haeckel, 1881, Prodromus, p. 455.

Definition.—Liosphærida forming a sphere of spongy framework, which encloses in the centre one single latticed medullary shell.

The genus Spongoplegma may be regarded as a Carposphæra, in which the simple latticed cortical shell is represented by an irregular spongy framework, immediately enclosing the simple latticed medullary shell.

1. Spongoplegma antarcticum, n. sp.

Cortical shell with loose spongy framework and rough surface, four to six times as broad as the enclosed simple medullary shell. Pores of the latter regular circular, twice as broad as the bars. From its surface arise numerous (forty to fifty or more) short radial beams, which become forked and compose, by communication of lateral branches, the spongy cortical shell.

Dimensions.—Diameter of the spongy cortical shell 0.2 to 0.3 of the latticed medullary shell 0.05 to 0.06.

Habitat.—Antarctic Ocean, in large number, together with Cromyosphæra antarctica; in the Diatom ooze of Station 157 (depth 1950 fathoms).

Genus 28. Spongodictyon,^[44] Haeckel, 1862, Monogr. d. Radiol., p. 459.

Definition.—Liosphærida forming a sphere of spongy framework, which encloses in the centre a double latticed concentric medullary shell.

The genus Spongodictyon can be regarded as a Thecosphæra, in which the simple latticed cortical shell is represented by an irregular spongy framework, which immediately encloses the double latticed medullary shell. Sometimes this latter appears triple, the inner surface of the spongy cortical shell forming a smooth spherical lattice-plate, separated by an interval from the double medullary shell.

Subgenus 1. Dictyoplegma, Haeckel, 1862, Monogr. d. Radiol, p. 458.

Definition.—Spongy cortical shell enveloping immediately the double medullary shell.

1. Spongodictyon spongiosum, Haeckel.