Legion I. SPUMELLARIA, (continued 7)

Habitat.—North Atlantic, Station 353, surface.

6. Echinomma trinacrium, Haeckel.

Actinomma trinacrium, Haeckel, 1862, Monogr. d. Radiol., p. 441, Taf. xxiv. figs. 6-8.

Cortical shell thin walled, with irregular, roundish pores, twice to three times as broad as the bars. Both medullary shells with regular, circular pores. Radial proportion of the three spheres = 1 : 3 : 9. On the surface about twenty three-sided pyramidal main spines, as long as the radius, and numerous (forty to sixty) by-spines of half the length. (Compare with this species Actinomma trinacrium, with which it is connected by transitional forms.)

Dimensions.—Diameter of the outer shell 0.09, middle 0.03, inner 0.01; cortical pores 0.008 to 0.012, bars 0.004; length of the spines 0.02 to 0.05, basal breadth 0.01.

Habitat.—Mediterranean (Messina).

7. Echinomma toxopneustes, n. sp. (Pl. 29, fig. 1).

Cortical shell thin walled, with large, irregular roundish, polygonally framed pores, twice to four times as broad as the crested bars. Both medullary shells of similar structure. Radial proportion of the three spheres = 1 : 2.5 : 6. Numerous (thirty to fifty or more) thin radial beams connecting them, prolonged outside into strong three-sided pyramidal spines, shorter than the radius; each of the three wings with two teeth. Between these, numerous smaller angular by-spines of one-quarter to one-half the length.

Dimensions.—Diameter of the outer shell 0.12, middle 0.05, inner 0.02; cortical pores 0.01 to 0.03, bars 0.008; length of the main spines 0.05, basal breadth 0.01.

Habitat.—South-east Pacific (South of Juan Fernandez), Station 300, surface.

Genus 103. Pityomma,^[139] Haeckel, 1881, Prodromus, p. 453.

Definition.—Astrosphærida with three concentric lattice-shells and numerous branched radial spines.

The genus Pityomma differs from its ancestral form, Actinomma, in the ramification of its radial spines, and exhibits therefore the same relation to it that Elatomma, among the Haliommida, bears to Haliomma.

1. Pityomma scoparium, n. sp.

Cortical shell thick walled, connected with both concentric medullary shells by twenty thin radial beams, which are prolonged outside into twenty large cylindrical radial spines; these are somewhat shorter than the shell radius, simple in the proximal inner half, irregularly branched in the outer half. All three spheres with regular, circular pores, twice to three times as broad as the bars; radial proportion = 1 : 2 : 6. (Similar to Cladococcus scoparius, Pl. 27, fig. 2, and Elatomma scoparium, but differs from both in the double medullary shell.)

Dimensions.—Diameter of the outer shell 0.15, middle 0.05, inner 0.025; length of the spines 0.1.

Habitat.—Central Pacific, Station 273, surface.

2. Pityomma piniferum, n. sp.

Cortical shell thin walled, with irregular, roundish pores, connected with both medullary shells by twenty stout radial beams, which are prolonged outside into twenty large three-sided prismatic spines. These are longer than the shell diameter and have three dentate edges, being branched like a pine tree (with four to six ramified branches on each edge, decreasing in size towards the distal end); similar to those of Cladococcus abietinus (Pl. 27, fig. 3). Radial proportion of the three spheres = 1 : 2 : 8. Both medullary shells with regular, circular pores, twice as broad as the bars.

Dimensions.—Diameter of the outer shell 0.2, middle 0.05, inner 0.025; length of the spines 0.25.

Habitat.—South Pacific, Station 299 (Juan Fernandez), surface.

3. Pityomma drymodes, n. sp. (Pl. 29, fig. 9).

Cortical shell thin walled, connected with both medullary shells by very numerous (one hundred to two hundred or more) very thin radial beams, which are prolonged outside into thin branched radial spines, scarcely half as long as the shell radius, each spine bearing six to nine simple branches. Outer and middle shell uneven, with hill-shaped protuberances and valleys between them; the connecting radial beams, which arise from the top of the protuberances of the middle shell, are inserted into the deepest part of the valleys of the outer shell. Radial proportion of the three spheres = 1 : 3 : 8. Outer medullary shell with small, irregular, roundish, or polygonal pores, not much broader than the bars; innermost shell with polygonal pores and very thin bars.

Dimensions.—Diameter of the outer shell 0.28, middle 0.1, inner 0.033; length of the spines 0.07, breadth 0.004.

Habitat.—Central Pacific, Station 271, surface.

Subfamily Cromyommida,^[140] Haeckel, 1881, Prodromus, pp. 449, 453.

Definition.—Astrosphærida with four concentric spherical lattice-shells.

Genus 104. Cromyomma,^[141] Haeckel, 1881, Prodromus, p. 454.

Definition.—Astrosphærida with four concentric lattice-spheres and numerous simple radial spines of one kind.

The genus Cromyomma is the common ancestral form of the Cromyommida, or of those Astrosphærida in which the shell is composed of four concentric spheres, connected by radial beams. Usually two of these are intracapsular or medullary shells, two extracapsular or cortical shells; the distance between the former and the latter is greater than the distance between either the two inner or the two outer shells. In some cases, however (e.g., Cromyomma zonaster), the distance between all four shells is equal.

Subgenus 1. Cromyommetta, Haeckel.

Definition.—Pores of the outer cortical shell regular, of nearly equal size and similar form.

1. Cromyomma villosum, n. sp. (Pl. 30, fig. 2).

Radial proportion of the four spheres = 1 : 2 : 4 : 5. Outer cortical shell thick walled, densely covered with innumerable bristle-shaped radial spines, half as long as the radius. Pores regular, circular, double-edged, of the same breadth as the bars; ten to twelve on the radius. The thick outer shell is so dark, that the outlines only of the other three shells can be seen.

Dimensions.—Diameter of the four shells—(A) outer cortical shell 0.2, (B) inner cortical shell 0.16, (C) outer medullary shell 0.08, (D) inner medullary shell 0.04; pores and bars of the outer shell 0.008; length of the spines 0.04.

Habitat.—Central Pacific, Station 267, depth 2700 fathoms.

2. Cromyomma zonaster, Haeckel.

Acanthosphæra zonaster, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 285, Taf. ii. fig. 2.

Radial proportion of the four spheres = 2 : 3 : 4 : 5. Outer cortical shell thick walled, densely covered with numerous bristle-shaped radial spines, as long as the radius. Pores regular, circular, twice as broad as the bars; eight to ten on the radius. The thick outer shell is so dark, that the outlines only of the other three shells can be seen.

Dimensions.—Diameter of the four shells—(A) 0.15, (B) 0.12, (C) 0.09, (D) 0.06; pores of the outer shell 0.01, bars 0.005; length of the spines 0.08.

Habitat.—Arctic Ocean, Greenland (depth 1000 fathoms), "Alert" Expedition.

3. Cromyomma perplexum, Stöhr.

Cromyomma perplexum, Stöhr, 1880, Palæontogr., vol. xxvi. p. 95, Taf. iii. fig. 5.

Radial proportion of the four spheres = 1 : 2 : 3 : 4. Outer cortical shell thick walled, densely covered with short conical spines, as long as the diameter of the pores. These are regular, circular, three times as broad as the bars; six to eight on the radius. The thick outer shell is so dark, that the outlines only of the three other shells can be seen.

Dimensions.—Diameter of the four shells—(A) 0.17, (B) 0.13, (C) 0.087, (D) 0.043; pores of the outer shell 0.015, bars 0.005; length of the spines 0.02.

Habitat.—Fossil in the Tertiary rocks of Sicily (Grotte) Stöhr.

Subgenus 2. Cromyommura, Haeckel.

Definition.—Pores of the outer cortical shell irregular, of different size and form.

4. Cromyomma perspicuum, n. sp. (Pl. 30, fig. 8).

Cromyosphæra perspicua, Haeckel, 1879, Atlas (pl. xxx. fig. 8).

Radial proportion of the four shells = 1 : 2.5 : 6 : 9. Outer cortical shell very thin walled, with thread-like bars, and irregular, polygonal pores; inner cortical shell with similar pores, but with thicker bars. Both medullary shells with regular, circular pores (the outer three times as broad as the inner). Numerous thin radial beams connect the latter with the former; other very thin and numerous beams connect the two cortical shells, and are prolonged outside into short bristle-shaped spines (often longer than in the figure).

Dimensions.—Diameter of the four shells—(A) 0.18, (B) 0.12, (C) 0.05, (D) 0.02; pores of the outer shell 0.01 to 0.02; length of the spines 0.01 to 0.03.

Habitat.—Central Pacific, Station 274, surface.

5. Cromyomma quadruplex, Haeckel.

Cromyomma quadruplex, Haeckel, 1862, Monogr. d. Radiol., p. 446.

Haliomma quadruplex, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 243.

Radial proportion of the four spheres = 1 : 3 : 7 : 10. Outer cortical shell thin walled, irregularly covered with numerous angular spines, as long as the radius. Pores of all four shells irregular, roundish, increasing in size from the first to the fourth.

Dimensions.—Diameter of the four shells—(A) 0.15, (B) 0.1, (C) 0.045, (D) 0.015; pores of the outer shell 0.01 to 0.02; length of the spines 0.07.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

6. Cromyomma macroporum, Stöhr.

Cromyomma macroporum, Stöhr, 1880, Palæontogr., vol. xxvi. p. 95, Taf. iii. fig. 4.

Radial proportion of the four spheres = 1 : 3 : 6 : 9. Outer cortical shell thick walled, densely covered with short conical spines, as long as the diameter of the pores; the latter are irregular, roundish, or polygonal, larger and smaller alternating.

Dimensions.—Diameter of the four shells—(A) 0.1, (B) 0.066, (C) 0.033, (D) 0.011; pores of the outer shell 0.033 to 0.016, bars 0.003; length of the spines 0.01.

Habitat.—Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.

7. Cromyomma circumtextum, n. sp. (Pl. 30, fig. 4).

Radial proportion of the four spheres = 1 : 2 : 5 : 7. Outer cortical shell very delicate and thin walled, with thread-like bars and large, irregular, polygonal meshes (larger than the innermost shell); inner cortical shell also with irregular, polygonal pores, three to nine times as broad as the thick bars. Both medullary shells with subregular, circular pores (the outer three times as broad as the inner). Radial spines twelve to twenty, three-sided prismatic, stout, piercing the three outer shells, inserted on the innermost; their outer part pyramidal, half as long as the radius.

Dimensions.—Diameter of the four shells—(A) 0.22, (B) 0.15, (C) 0.07, (D) 0.03; meshes of the outer shell 0.02 to 0.04; length of the outer spines 0.05.

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

8. Cromyomma mucronatum, n. sp. (Pl. 30, figs. 5, 5a).

Radial proportion of the three spheres = 1 : 2 : 3 : 6. Outer cortical shell thin walled, with large, irregular, roundish pores and crested three-sided bars; inner cortical shell with regular, circular, hexagonally formed pores (four times as broad as the bars). Both medullary shells with simple, small, regular, circular pores (fig. 5a). Twelve radial spines three-sided prismatic, dagger-shaped, with three teeth, as long as the diameter of the innermost shell.

Dimensions.—Diameter of the four shells—(A) 0.24, (B) 0.12, (C) 0.08, (D) 0.04; meshes of the outer shell 0.02 to 0.04; length of the spines 0.04.

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

Genus 105. Cromyechinus,^[142] Haeckel, 1881, Prodromus, p. 454.

Definition.—Astrosphærida with four concentric lattice-spheres and numerous simple spines of two different kinds; larger main spines and smaller by-spines.

The genus Cromyechinus differs from Cromyomma in the same way as Echinomma from Actinomma; the radial spines being differentiated into two different kinds; a larger number of small by-spines, and a smaller number of large main spines.

1. Cromyechinus icosacanthus, n. sp. (Pl. 30, fig. 1).

Radial proportion of the three spheres = 1 : 2 : 6 : 8. Outer cortical shell very delicate, with very small, regular, circular pores, covered with very numerous bristle-shaped by-spines, half as long as the radius; inner cortical shell with very large, irregular, polygonal pores, three to eight times as broad as the bars. Both medullary shells with regular, circular pores, connected with the former by twenty regularly disposed, very thin bars; these are prolonged outside into twenty very stout, three-sided prismatic main spines, as long as the radius, which arise from the inner cortical shell, and at the distal end are cuspidate.

Dimensions.—Diameter of the four shells—(A) 0.16, (B) 0.13, (C) 0.04, (D) 0.02; pores of the outer cortical shell 0.003, of the inner 0.03, bars 0.003; length of the spines 0.08.

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

2. Cromyechinus dodecacanthus, n. sp. (Pl. 30, figs. 3, 3a).

Radial proportion of the four spheres = 1 : 3 : 10 : 12. Outer cortical shell very delicate, with very small, regular, circular pores, covered with numerous short bristle-shaped by-spines, scarcely one-fourth as long as the radius; inner cortical shell with very large, irregular, polygonal pores, twice to six times as broad as the bars. Both medullary shells with very small, regular, circular pores, connected with the former by twelve regularly disposed, thin radial beams; these are prolonged outside into twelve strong, three-sided pyramidal main spines, one-third as long as the shell diameter. (Differs from the foregoing only in the number and form of the radial spines.)

Dimensions.—Diameter of the four shells—(A) 0.12, (B) 0.1, (C) 0.03, (D) 0.01; pores of the outer cortical shell 0.002, of the inner 0.02, bars 0.002; length of the spines 0.04, basal breadth 0.01.

Habitat.—South Atlantic, Station 325, surface.

3. Cromyechinus polyacanthus, n. sp.

Radial proportion of the four spheres = 1 : 2 : 8 : 10. Outer cortical shell of the same structure as the inner, with irregular, roundish pores, twice to six times as broad as the bars. Both medullary shells with small, regular, circular pores, twice as broad as the bars. Connecting radial beams forty to sixty, thin, cylindrical, prolonged outside into forty to sixty strong conical main spines, about as long as the radius. Between these, numerous thin bristle-shaped by-spines, nearly of the same length.

Dimensions.—Diameter of the four shells—(A) 0.25, (B) 0.2, (C) 0.05, (D) 0.025; pores of both cortical shells 0.01 to 0.03; length of the spines 0.12.

Habitat.—North Pacific, Station 237, surface.

Genus 106. Cromyodrymus,^[143] Haeckel, 1881, Prodromus, p. 454.

Definition.—Astrosphærida with four concentric lattice-spheres and numerous branched radial spines.

The genus Cromyodrymus differs from its ancestral form, Cromyomma, in the ramification of the radial spines, and exhibits therefore the same relation to it that Pityomma among the Actinommida bears to Actinomma.

1. Cromyodrymus quadricuspis, n. sp. (Pl. 30, figs. 7, 7a).

Radial proportion of the four shells = 1 : 3 : 6 : 12. All four shells with regular, circular pores, about twice as broad as the bars. Radial proportion of the pores in the four shells = 2 : 4 : 2 : 1. Radial spines fifty to sixty, three-sided prismatic, half as long as the radius, with three recurved teeth, each spine in this way bearing four points.

Dimensions.—Diameter of the four shells—(A) 0.16, (B) 0.08, (C) 0.04, (D) 0.013; length of the spines 0.03 to 0.04, breadth 0.007.

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

2. Cromyodrymus abietinus, n. sp. (Pl. 30, fig. 6).

Radial proportion of the four shells = 1 : 2 : 5 : 11. All four shells with irregular, roundish pores, twice to four times as broad as the bars. Radial proportion of the pores in the four shells = 9 : 3 : 2 : 1. Radial spines eighty to one hundred and twenty, about as long as the radius, branched like a pine tree, with six to twelve ramified branches.

Dimensions.—Diameter of the four shells—(A) 0.22, (B) 0.1, (C) 0.04, (D) 0.02; length of the spines 0.12, breadth 0.006.

Habitat.—South-east Pacific (Juan Fernandez), Station 299, surface.

Subfamily Caryommida,^[144] Haeckel.

Arachnosphærida, Haeckel, 1862, Monogr. d. Radiol., p. 354; Prodromus, 1881, p. 454.

Definition.—Astrosphærida with five or more concentric spherical lattice-shells.

Genus 107. Caryomma,^[145] n. gen.

Definition.—Arachnosphærida with five to six or more concentric spherical lattice-shells; two inner (intracapsular) medullary and three or more outer (extracapsular) cortical shells, composed of ordinary lattice-work; distance between the former and the latter greater than between any other two shells.

The genus Caryomma may be regarded as a Cromyomma, in which the number of the cortical shells is increased to three, four, or more. These lie outside the central capsule, whilst two medullary shells lie within it, and are connected with the former by numerous radial spines piercing the wall of the capsule. The ordinary lattice-work is not arachnoidal, as in the three following genera.

1. Caryomma regulare, n. sp.

Radial proportion of the five shells = 1 : 2 : 6 : 8 : 10. All five shells with regular, circular pores, twice to three times as broad as the bars, and gradually increasing in size from the innermost to the outermost shell. Radial beams connecting them twenty, prolonged on the surface into twenty stout, three-sided pyramidal, radial spines, half as long as the radius, regularly disposed.

Dimensions.—Diameter of the five shells—(A) 0.25, (B) 0.2, (C) 0.15, (D) 0.05, (E) 0.025.

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

2. Caryomma irregulare, n. sp.

Radial proportion of the six shells = 1 : 2.5 : 8 : 10.5 : 13 : 15. Both inner (medullary) shells with regular, circular pores, the other four (cortical) shells with irregular, roundish pores, gradually increasing in size from the innermost to the outermost shell. Radial spines sixty to eighty, pyramidal, irregularly disposed.

Dimensions.—Diameter of the six shells—(A) 0.3, (B) 0.26, (C) 0.21, (D) 0.16, (E) 0.05, (F) 0.02.

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

Genus 108. Arachnopila,^[146] n. gen.

Definition.—Astrosphærida with five to ten or more cortical, concentric, polyhedral, or spherical lattice-shells, composed of a very thin cobweb-like network; innermost shell with hexagonal (regular) or polygonal (irregular) meshes; other shells with simple triangular meshes, without diagonal threads between them.

The genus Arachnopila, together with the two following genera, forms the peculiar small group of large Arachnosphærida, separated from the true Caryommida by the totally different structure and disposition of the numerous concentric shells; the former exhibits a similar relation to the latter that the Diplosphærida bears to the Elatommida among the dispherical Haliommida. The concentric shells (five to ten or more) lie outside the central capsule, and are composed of very delicate, cobweb-like threads. From the innermost shell arise numerous, three-sided prismatic, very long spines, from which at equal regular distances arise lateral branches (three pairs from each spine, and one pair from each corner). In Arachnopila these threads pass directly from one spine to the other, and form simple, large, triangular meshes between them. The concentric shells are not connected by interwoven diagonal threads.

1. Arachnopila hexagonella, n. sp.

Innermost shell with regular hexagonal pores; its diameter twice as long as the equal distance between every two concentric shells. Radial spines twenty to forty, each with twenty to twenty-four verticils.

Dimensions.—Diameter of the innermost shell 0.1; distance between the concentric shells 0.05.

Habitat.—Central Pacific, Station 271, surface.

2. Arachnopila polygonella, n. sp.

Innermost shell with irregular, polygonal pores; its diameter fully as long as the equal distance between every two concentric shells. Radial spines sixty to eighty, each with twelve to sixteen verticils.

Dimensions.—Diameter of the innermost shell 0.04; distance between the concentric shells 0.04.

Habitat.—Central Pacific, Station 266, surface.

Genus 109. Arachnopegma,^[147] Haeckel, 1881, Prodromus, p. 454.

Definition.—Astrosphærida with five to ten or more cortical, concentric, polyhedral, or spherical lattice-shells, composed of a very thin, cobweb-like network; innermost shell with hexagonal or polygonal meshes; other shells with simple triangular meshes, connected to one another by diagonal threads between them.

The genus Arachnopegma differs from its ancestral form Arachnopila, in the possession of peculiar diagonal threads, which connect the verticils or nodal-points of every two neighbouring radial spines in two different neighbouring concentric shells. In this case, therefore, not only do triangular meshes lie in the spherical faces of the concentric spheres, but also between them, in numerous oblique diagonal planes; a very rare and remarkable structure, and forming a transition to spongy shells.

1. Arachnopegma verticillatum, n. sp.

Innermost shell with regular, hexagonal meshes; its diameter is the same as the equal distance between each of the two shells. Threads of the network smooth. Radial spines twenty to forty, each with fifteen to twenty verticils.

Dimensions.—Diameter of the innermost shell 0.04, distance between the concentric shells 0.03 to 0.04.

Habitat.—Central Pacific, Station 266, surface.

2. Arachnopegma longispinum, n. sp.

Innermost shell with regular, hexagonal meshes; its diameter half as large as the equal distance between every two shells. Threads of the network dentated or with small knots. Radial spines fifty to sixty, each with twenty to twenty-five verticils.

Dimensions.—Diameter of the innermost shell 0.02; distance between the concentric shells 0.04 to 0.05.

Habitat.—Central Pacific, Station 272, surface.

3. Arachnopegma increscens, n. sp.

Innermost shell with regular, hexagonal meshes; its diameter quite as large as the distance between it and the second shell; only half as large as the distance between the fourth and fifth shells. Forty to fifty radial spines, each with fifteen to twenty verticils.

Dimensions.—Diameter of the innermost shell (A) 0.025; distance between the following shells—A, B = 0.025, B, C = 0.03, C, D = 0.04, D, E = 0.048, E, F = 0.056, F, G = 0.064, &c.

Habitat.—Central Pacific, Station 274, surface.

Genus 110. Arachnosphæra,^[148] Haeckel, 1862, Monogr. d. Radiol., p. 355.

Definition.—Astrosphærida with five to ten or more cortical, concentric, polyhedral, or spherical lattice-shells, composed of a very thin cobweb-like network; innermost shell with hexagonal (regular) or polygonal (irregular) meshes; other shells with larger, irregular, polygonal meshes.

The genus Arachnosphæra (accurately described by me in 1862, loc. cit.) differs from the two preceding genera in the irregular form of the large meshes in all shells (except often the innermost). This is caused by the ramification of the thin threads, which on each shell connect the neighbouring spines. In Arachnopila and Arachnopegma the threads pass directly and undivided from each spine to the neighbouring spine (three pairs from the three edges), and therefore all meshes are triangular. In Arachnosphæra they become polygonal by irregular ramification of the threads. There are here no diagonal threads.

Subgenus 1. Arachnosphærella, Haeckel.

Definition.—Pores of the innermost shell regular, hexagonal.

1. Arachnosphæra oligacantha, Haeckel.

Arachnosphæra oligacantha, Haeckel, 1862, Monogr. d. Radiol., p. 356, Taf. x. fig. 2, Taf. xi. fig. 3.

Innermost shell with regular, hexagonal meshes; its diameter three times as long as the equal distances between every two concentric shells. Fifteen to twenty radial spines scattered at wide intervals, each with six to eight verticils.

Dimensions.—Diameter of the innermost shell 0.12; distance between the concentric shells 0.04 to 0.05.

Habitat.—Mediterranean (Messina), surface, Haeckel.

2. Arachnosphæra myriacantha, Haeckel.

Arachnosphæra myriacantha, Haeckel, 1862, Monogr. d. Radiol., p. 357, Taf. x. fig. 3, Taf. xi. fig. 4.

Innermost shell with regular, hexagonal meshes; its diameter twice as long as the equal distances between every two concentric shells. At each nodal-point occurs one radial spine with six to eight verticils (spines in all one hundred to one hundred and twenty or more).

Dimensions.—Diameter of the innermost shell 0.1; distance between the concentric shells 0.04 to 0.05.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

3. Arachnosphæra dolichacantha, n. sp.

Innermost shell with regular, hexagonal meshes, very small; its diameter only as long as the equal distances between every two concentric shells. At each nodal-point occurs one radial spine with twelve to sixteen verticils (altogether thirty to forty spines).

Dimensions.—Diameter of the innermost shell 0.05; distance between the concentric shells 0.04 to 0.05.

Habitat.—Central Pacific, Station 265 to 274, surface.

4. Arachnosphæra increscens, n. sp.

Innermost shell with regular, hexagonal meshes; its diameter three times as long as the distance between it and the second shell, quite as long as the distance between the fifth and sixth shells; the distances between the concentric shells gradually increasing from the centre. Radial spines about fifty to sixty, each with six to eight verticils.

Dimensions.—Diameter of the innermost shell (A) 0.75; distances between the following shells—A, B = 0.025, B, C = 0.037, C, D = 0.05, D, E = 0.062, E, F = 0.075, &c.

Habitat.—Central Pacific, Station 271, surface.

Subgenus 2. Arachnosphæromma, Haeckel.

Definition.—Pores of the innermost shell irregular, polygonal.

5. Arachnosphæra tenuissima, n. sp.

Innermost shell with irregular, polygonal meshes; its diameter twice as long as the equal distance between every two concentric shells. Forty to fifty radial spines, each with twelve to sixteen verticils.

Dimensions.—Diameter of the innermost shell 0.1, distance between the concentric shells 0.04 to 0.05.

Habitat.—South Atlantic, Station 332, surface.

6. Arachnosphæra velaris, n. sp.

Innermost shell with irregular, polygonal meshes; its diameter twice as long as the distance between it and the second shell, quite as long as the distance between the third and fourth shells; the distance between the concentric shells gradually increasing from the centre. Radial spines twenty to thirty, each with ten to twelve verticils.

Dimensions.—Diameter of the innermost shell (A) 0.5; distances of the following shells—A, B = 0.025, B, C = 0.037, C, D = 0.05, D, E = 0.062, E, F = 0.075.

Habitat.—Tropical Atlantic, Station 347, surface.

Subfamily Spongiommida,^[149] Haeckel.

Definition.—Astrosphærida with spongy spherical or polyhedral shell (with or without enclosed concentric lattice-shells).

Genus 111. Spongiomma,^[150] n. gen.

Definition.—Astrosphærida with solid spongy sphere, with numerous simple radial spines, but without latticed medullary shells.

The genus Spongiomma differs from its ancestral form, Styptosphæra, in the development of simple radial spines on the surface of the solid sphere, the entire mass of which is composed of an irregular, spongy wicker-work.

Subgenus 1. Spongiommella, Haeckel.

Definition.—Radial spines on the surface of the spongy sphere all of the same shape.

1. Spongiomma radiatum, n. sp.

Spongy framework of the solid sphere of the same structure throughout, with small, irregular, polyhedral meshes and very thin thread-like bars. From the surface arise very numerous (one hundred and twenty to one hundred and sixty or more) straight, bristle-shaped radial spines, as long as the radius of the sphere (counting from the middle part of it).

Dimensions.—Diameter of the spongy sphere 0.2; length of the radial spines 0.1.

Habitat.—Central Pacific, Station 272, surface.

2. Spongiomma denticulatum, n. sp.

Spongy framework of the solid sphere of the same structure throughout, with small, almost equal meshes, four to eight times as broad as the thin, elegantly denticulated bars; from the surface arise very numerous (two hundred to three hundred or more) curved, radial spines, as long as the radius, and of the same form as the bars.

Dimensions.—Diameter of the sphere 0.25; length of the spines 0.12.

Habitat.—Central Pacific, Station 274, surface.

3. Spongiomma spathillatum, n. sp.

Spongy framework in the central part of the sphere much denser and darker, and with smaller meshes than in the peripheral part in which are very thin bars. Entire surface covered with innumerable short, bristle-shaped radial spines, only one-eighth as long as the radius, of the same elegant form as in Octodendron spathillatum (Pl. 18, figs. 2, 4); each spine developed in a zig-zag fashion, with very small beards, with a delicate spathillum (or coronal of beard spines) at the distal end.

Dimensions.—Diameter of the spheres 0.16; length of the spines 0.01.

Habitat.—South Pacific, Station 295, surface.

4. Spongiomma clavatum, n. sp.

Spongy framework in the central part of the sphere much denser and darker than in the peripheral part. On the surface are sixty to eighty stout, club-shaped radial spines, as long as the radius of the sphere, in the proximal half three-sided prismatic, with three dentated edges; they begin at the middle of the radius (where the denser inner framework changes into the looser outer) and are very thin at first but increase slowly in thickness towards the truncated distal end. (Similar to Centrocubus rhopalophorus, Pl. 18, fig. 1, but without the cubical medullary shell.)

Dimensions.—Diameter of the sphere 0.4; length of the spines 0.2.

Habitat.—North Pacific, Station 241, surface.

Subgenus 2. Spongiommura, Haeckel.

Definition.—Radial spines on the surface of the spongy sphere of two different kinds; large main spines and small by-spines.

5. Spongiomma helioides, n. sp.

Spongy framework of the sphere everywhere of the same structure, with almost equal meshes, ten to twelve times as broad as the bars. Sixteen to twenty radial main spines, longer than the shell diameter, three-sided prismatic, with three serrated edges, beginning about the middle of the radius and increasing in thickness to the truncated distal end. Between them occur numerous thin, bent, bristle-shaped by-spines. (Very similar to Spongosphæra helioides, Monogr. d. Radiol., Taf. xii. figs. 11-13, but without medullary shells.)

Dimensions.—Diameter of the sphere 0.3; length of the main spines 0.4, of the by-spines 0.01.

Habitat.—Tropical Atlantic, Station 352, surface.

6. Spongiomma multiaculeum, Haeckel.

Spongechinus multiaculeatus, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. xlv. p. 29, Taf. v. figs. 60-63.

Spongy framework of the sphere very compact, with small meshes, scarcely broader than the bars; four to eight large main spines, three-sided pyramidal, longer than the shell radius; numerous (thirty to forty) thin by-spines, scarcely half as long.

Dimensions.—Diameter of the sphere 0.16; length of the main spines 0.11, of the by-spines 0.03.

Habitat.—Fossil in the Alpine Jura, Schafberg near Salzburg (Dunikowski).

7. Spongiomma asteroides, n. sp.

Spongy framework in the central part of the sphere much denser and darker than in the peripheral part. Sixty to eighty cylindro-conical main spines, as long as the radius, between them are numerous straight, bristle-shaped by-spines half that length.

Dimensions.—Diameter of the sphere 0.28; length of the main spines 0.16, of the by-spines 0.08.

Habitat.—South Atlantic, Station 325, surface.

Genus 112. Spongodrymus,^[151] Haeckel, 1881, Prodromus, p. 456.

Definition.—Astrosphærida with solid spongy sphere, without latticed medullary shell, with numerous branched radial spines.

The genus Spongodrymus differs from the preceding Spongiomma in the ramification of the numerous radial spines, covering the surface of the solid spongy sphere.

1. Spongodrymus elaphococcus, n. sp. (Pl. 18, fig. 9).

Spongy framework of the solid sphere equal throughout, on the surface arising in the form of very numerous (sixty to eighty or more) spongy cones with rather rhomboidal meshes. Each cone is prolonged into a very thin, irregularly curved radial spine, which is twice as long as the shell diameter, simple in the proximal half, branched like a tree in the distal half; each arborescent spine has from sixteen to thirty-two terminal branches, which fall in one spherical face. The branches of neighbouring spines are partly connected by anastomoses, so that they begin to form an outer spherical shell (cortical shell) with a looser spongy framework.

Dimensions.—Diameter of the whole spherical skeleton (sphere formed by the distal ends of the dichotomous branches) 0.9, of the inner solid spongy sphere 0.02.

Habitat.—Tropical Atlantic, Station 349, surface.

2. Spongodrymus abietinus, n. sp.

Spongy framework denser and darker in the central part of the sphere than in the peripheral part, with rather coarse meshes and thick bars. From the surface arise very numerous (sixty to eighty) stout, radial branches, as long as the shell radius, branched like a pine tree (with six to twelve ramified branches). Similar in structure to Cromyodrymus abietinus (Pl. 30, fig. 6), but with a quite irregular spongy texture in the central sphere.

Dimensions.—Diameter of the sphere 0.3; length of the spines 0.015.

Habitat.—Central Pacific, Station 272, surface.

Genus 113. Spongechinus,^[152] Haeckel, 1881, Prodromus, p. 456.

Definition.—Astrosphærida with hollow, spongy sphere, without latticed medullary shell in the central cavity, and with numerous simple radial spines.

The genus Spongechinus differs from its ancestral form, Plegmosphæra, in the development of numerous radial spines on the surface of the spongy sphere, within which is enclosed a large spherical central cavity.

1. Spongechinus setosus, n. sp.

Spongy sphere three times as broad as its inner cavity, with a very delicate, equal framework. Entire surface covered with short, straight, bristle-shaped radial spines, about half as long as the radius.

Dimensions.—Diameter of the sphere 0.2, of its inner cavity 0.07; length of the spines 0.05.

Habitat.—North Atlantic, Azores, surface.

2. Spongechinus serrulatus, n. sp.

Spongy sphere twice as broad as its inner cavity, with a delicate, equal framework. Entire surface covered with short, curved, radial spines, which are elegantly denticulated, and as long as the shell radius.

Dimensions.—Diameter of the sphere 0.3, of its cavity 0.15; length of the spines 0.15.

Habitat.—Central Pacific, Station 274, surface.

3. Spongechinus cavus, n. sp.

Spongy sphere only one-fourth broader than the large inner cavity, its spongy wall being only one-fourth as thick as the radius, composed of three to four strata of irregular, small meshes. Surface covered with short, bristle-shaped, curved spines, one-third as long as the radius.

Dimensions.—Diameter of the sphere 0.5, of its inner cavity 0.4; length of the spines 0.08.

Habitat.—North Atlantic, Station 354, surface.

Genus 114. Spongothamnus,^[153] n. gen.

Definition.—Astrosphærida with hollow, spongy sphere, without latticed medullary shell in the central cavity, and with numerous branched radial spines.

The genus Spongothamnus differs from the preceding Spongechinus in the ramification of the numerous radial spines, covering the surface of the hollow spongy sphere; it therefore exhibits the same relation to the latter that Spongodrymus bears to Spongiomma.

1. Spongothamnus furcatus, n. sp.

Spongy sphere twice as broad as its inner cavity, with very delicate bars, and irregular, dense framework. From the surface arise one hundred and fifty to one hundred and eighty thin, forked, bristle-shaped spines, half as long as the radius; both fork branches one-third as long as the basal or simple part.

Dimensions.—Diameter of the sphere 0.3, of its inner cavity 0.15; length of the spines 0.08.

Habitat.—North Pacific, Station 241, surface.

2. Spongothamnus scoparius, n. sp.

Spongy sphere four times as broad as its inner cavity, with thick bars and rather loose framework. From the surface arise sixty to eighty broom-shaped radial spines, as long as the radius, each in the basal half simple, in the distal half with six to twelve irregularly ramified branches (similar to the spines of Cromyodrymus abietinus, Pl. 30, fig. 6).

Dimensions.—Diameter of the sphere 0.4, of the inner cavity 0.1; length of the spines 0.2.

Habitat.—Central Pacific, Station 271, surface.

Genus 115. Spongopila,^[154] Haeckel, 1881, Prodromus, p. 456.

Definition.—Astrosphærida with a single, spherical, latticed medullary shell, immediately enveloped by the spongy framework of the cortical shell; on the surface of the latter are numerous radial spines.

The genus Spongopila is a Spongoplegma with radial spines. On the other hand it may be derived either from Elaphococcus, by communication of the branched spines, or from Arachnosphæra, by development of spongy branches between the concentric spheres.

1. Spongopila dichotoma, n. sp.

Medullary shell with regular, hexagonal meshes, six times as broad as the bars. From each nodal-point (between every three meshes) arises a bristle-shaped radial spine, which is dichotomously branched. By communication of the neighbouring branches the loose spongy framework of the spherical cortical shell is formed, which is four times as broad as the medullary shell. On the surface occur very numerous bristle-shaped radial spines, as long as the diameter of the medullary shell. (May be derived from Elaphococcus.)

Dimensions.—Diameter of the spongy cortical shell 0.3, of the medullary shell 0.08.

Habitat.—Tropical Atlantic, Station 347, surface.

2. Spongopila verticillata, n. sp.

Medullary shell with regular, hexagonal meshes, four times as broad as the bars. From its surface arise forty to sixty, three-sided prismatic radial spines, bearing eight to ten verticils of lateral branches, each verticil with six forked branches (two from each edge). By irregular ramification of these branches, and communication in all directions, the loose spongy framework of the cortical shell originates, which is six times as broad as the medullary shell. The free distal ends of the spines are as long as the shell radius. (May be derived from Arachnosphæra.)

Dimensions.—Diameter of the spongy cortical shell 0.6, of the medullary shell 0.1.

Habitat.—Tropical Pacific, Station 200, surface.

Genus 116. Rhizoplegma,^[155] Haeckel, 1881, Prodromus, p. 456.

Definition.—Astrosphærida with a single, spherical, latticed medullary shell, which is not armed with by-spines, but connected by stout radial main spines with the spongy cortical shell.

The genus Rhizoplegma is immediately allied to the foregoing Spongopila, but differs from it in the large interval separating both shells. In this interval lies the wall of the central capsule, which is only pierced by the radial spines connecting both shells.

Subgenus 1. Rhizoplegmarium, Haeckel.

Definition.—No free lateral branches of the radial spines between the two shells.

1. Rhizoplegma polyacanthum, n. sp.

Spongy cortical shell with a very fine dense framework and nearly smooth surface (without superficial by-spines). Its inner cavity is four times as broad as the medullary shell, which exhibits regular, hexagonal meshes. Radial spines sixty to eighty, three-sided prismatic, with three smooth edges, without lateral branches between both shells; their free outer part as long as the shell radius.

Dimensions.—Diameter of the spongy cortical shell 0.3, of its inner cavity 0.2, of the medullary shell 0.05.

Habitat.—Central Pacific, Station 274, surface.

2. Rhizoplegma spirale, n. sp.

Spongy cortical shell with a very delicate loose framework and bristly surface. Its inner cavity three times as broad as the medullary shell, which exhibits regular, hexagonal meshes. Radial spines thirty to forty, prismatic, with three smooth, spirally contorted edges, without lateral branches between the two shells; their free outer part half as long as the shell radius.

Dimensions.—Diameter of the spongy cortical shell 0.2, of its inner cavity 0.12, of the medullary shell 0.04.

Habitat.—Central Pacific, Station 265, surface.

3. Rhizoplegma trigonacantha, n. sp.

Spongy cortical shell with a rather loose framework and coarse bars, with nearly smooth surface (without by-spines). Its inner cavity twice as broad as the medullary shell, which exhibits irregular, roundish pores. Radial spines forty to sixty, prismatic, with three smooth straight edges, without free branches between the two shells; their outer pyramidal part only one-third of the shell radius. (Very similar to the common Rhizosphæra trigonacantha, but with simple medullary shell.)

Dimensions.—Diameter of the spongy shell 0.2, of its inner cavity 0.16, of the medullary shell 0.08.

Habitat.—North Atlantic, Station 353, surface.

Subgenus 2. Rhizoplegmidium, Haeckel.

Definition.—Between the two shells free lateral branches arise from the three edges of the radial spines.

4. Rhizoplegma radicatum, n. sp. (Pl. 15, figs. 9, 9a).

Spongy cortical shell with a very loose framework; on the surface are innumerable thin, forked, or repeatedly dichotomous by-spines. Its inner cavity three times as broad as the medullary shell, which exhibits regular, hexagonal meshes (fig. 9a). Radial spines twelve, prismatic, with straight dentated edges, their outer pointed part as long as the shell radius. Each spine between the two shells has a verticil of three forked lateral branches (fig. 9a). The central capsule completely distends the medullary shell, and forces out through each mesh a hernia-shaped process (fig. 9).

Dimensions.—Diameter of the spongy shell 0.5, of its inner cavity 0.25, of the medullary shell 0.08.

Habitat.—Central Pacific, Station 271, surface.

5. Rhizoplegma lychnosphæra, n. sp. (Pl. 11, fig. 5).

Lychnosphæra rhizoplegma, Haeckel, 1879, Atlas (pl. xi. fig. 5).

Spongy cortical shell with a very loose framework, composed of long thin beams as in Lychnosphæra regina (Pl. 11, figs. 1-4). Surface covered with short bristles. Its inner cavity six times as broad as the medullary shell, which exhibits regular, hexagonal meshes. Radial spines twelve, prismatic, with three smooth edges; their outer pointed part half as long as the shell radius. Each spine has three verticils of three forked branches; the first verticil is free between the two shells, while the two following verticils, by communication of their ramules, form the irregular framework. Central capsule with many herniæ, forced out through the meshes of the medullary shell (fig. 5).

Dimensions.—Diameter of the spongy shell 0.7, of its inner cavity 0.45, of the medullary shell 0.07.

Habitat.—South Pacific, Station 284, surface.

Genus 117. Lychnosphæra,^[156] Haeckel, 1881, Prodromus, p. 453.

Definition.—Astrosphærida with a single, spherical, latticed medullary shell, which is armed with free radial by-spines, and connected by stout radial main spines with the spongy cortical shell.

The genus Lychnosphæra, known only by one single, large, and very remarkable species, mainly differs from the foregoing in the development of free radial by-spines on the surface of the medullary shell, and in the free interval between it and the cortical shell; but beyond this the loose spongy framework of the latter exhibits a very remarkable structure, figured in Pl. 11.

1. Lychnosphæra regina (Pl. 11, figs. 1-4).

Medullary shell (fig. 3) with regular, circular, hexagonally framed pores, twice as broad as the bars; from each hexagon-corner arises a radial, bristle-shaped by-spine, as long as the diameter. Twelve radial main spines each as broad as one of the meshes, three-sided prismatic, six to eight times as long as the medullary shell. From their three leaf-shaped (often somewhat denticulated or spirally contorted) edges arise four verticils of lateral branches, each composed of three forked, thin branches. The forked branches of the first verticil end free between the two shells (figs. 2, 3), while the two following verticils are ramified, and, by anastomosis of their branches, compose the loose spongy framework of the cortical shell. On the surface of the latter arise numerous radial (zig-zag-shaped) by-spines. The fourth verticil is terminal, with three shorter, thicker, dentated, simple branches, which constitute, together with the distal apex of the spine itself, a bunch of four terminal spines. The large central capsule completely distends the medullary shell, and forces out by its pores numerous club-shaped herniæ (fig. 1).

Dimensions.—Diameter of the spongy cortical shell 0.6, of its inner cavity 0.4, of the central capsule 0.22, of the medullary shell 0.06; length of the radial spines 0.4, breadth 0.01.

Habitat.—Central Pacific, Station 271, surface.

Genus 118. Centrocubus,^[157] n. gen.

Definition.—Astrosphærida with a single, cubical medullary shell, immediately surrounded by the spongy framework of the cortical shell; from the eight corners of the central cube arise eight primary radial spines, and often others from the framework between them.

The genus Centrocubus and the following closely allied Octodendron may represent a peculiar small group of Spongiommida, remarkable for the regular, cubical form of the medullary shell, which is composed of twelve thin rods, corresponding to the twelve edges of a mathematical cube; from the eight corners invariably arise eight primary radial spines, the branches of which form the spongy cortical shell.

1. Centrocubus octostylus, n. sp.

Radial spines eight, arising from the eight corners of the cubiform, regular, medullary shell, gradually increasing in thickness towards the club-shaped distal end, which is five to six times as broad as the central end. From the three denticulate edges of each spine arise six to eight lateral branches, which ramify irregularly and form by their anastomosis the spongy framework which is of nearly similar structure throughout, and with large loose meshes. The free distal part of each spine is half as long as the enclosed part.

Dimensions.—Diameter of the sphere 0.6, of the central cube 0.02; length of the spines 0.15, distal thickness 0.02.

Habitat.—Central Pacific, Station 271, surface.

2. Centrocubus cladostylus, n. sp. (Pl. 18, fig. 1).

Radial spines thirty-two, club-shaped, at the distal end eight to ten times as broad as at the basal end. Eight primary spines arise from the eight corners of the regular, cubiform medullary shell, and from these, in the form of lateral branches, twenty-four secondary spines arise with concavely curved bases (three from the three denticulate edges of each spine, at nearly equal distances from the centre). The free distal end of each of the thirty-two spines is of the same shape, about half as long as the radius of the spongy sphere; framework much looser in the outer than in the inner part.

Dimensions.—Diameter of the sphere 0.8, of the central cube 0.02; length of the spines 0.2, distal thickness 0.02.

Habitat.—North Pacific, Station 256, surface.

3. Centrocubus polystylus, n. sp.

Radial spines sixty to eighty, club-shaped, four to six times as broad at the distal as at the basal end. Eight primary spines arise from the eight corners of the regular, cubiform medullary shell, the remainder either springing as lateral branches from the three denticulate corners of the former, or arising within the spongy framework, which is much denser and darker in the central than in the peripheral part. The free distal end of each spine is one-third as long as the radius.

Dimensions.—Diameter of the sphere 0.9, of the central cube 0.02; length of the spines 0.15, distal thickness 0.02.

Habitat.—South Pacific, Station 295, surface.

Genus 119. Octodendron,^[158] n. gen.

Definition.—Astrosphærida with a single, cubical medullary shell, and eight primary radial spines arising from its eight corners; these are connected at equal distances by a latticed, spherical, cortical shell, from which the spongy framework directly springs; often from the latter secondary radial spines arise.

The genus Octodendron has the same regular, cubical medullary shell as the preceding Centrocubus, but differs from it in the wide interval separating the medullary shell from the inner spherical face of the spongy cortical shell, the two being connected only by eight radial beams, arising from the eight corners of the cube.

Subgenus 1. Octodendridium, Haeckel.

Definition.—Only eight primary radial spines, arising from the eight corners of the central cube.

1. Octodendron cubocentron, n. sp. (Pl. 18, fig. 3).

Radial spines eight, club-shaped, with three denticulate, straight edges, twice as long as the diameter of the central cavity of the cubical spongy shell; the inner face of the latter (or the "inner cortical shell") exhibits the form of a large cube, the spongy sides of which are parallel with the simple square sides of the central cube. The thin eight radial beams, connecting the corresponding corners of both cubes, are not thicker than the edge-bars of the central cube, whilst their outer prolongations are much thicker, with four to six verticils of lateral branches. Surface of the thin walled, loose, spongy shell armed with short simple thorns.

Dimensions.—Diameter of the spongy shell 0.2, of its inner cavity 0.1, of the central cube 0.02; length of the spines 0.2 (from the centre 0.3).

Habitat.—Central Pacific, Station 266, surface.

2. Octodendron spirale, n. sp.

Radial spines eight, three-sided prismatic, three times as long as the diameter of the inner shell-cavity; their three edges denticulated and spirally contorted around the spine axis. Thickness of the loose spongy shell-wall equal to the radius of the inner cavity, three times as large as the central cube. Surface covered, with numerous thin, bristle-shaped, bent spinules.

Dimensions.—Diameter of the spongy shell 0.24, of its inner cavity 0.12, of the central cube 0.02; length of the spines 0.4, breadth 0.01.

Habitat.—North Pacific, Station 254, surface.

3. Octodendron pinetum, n. sp.

Radial spines eight, three-sided prismatic, three to four times as long as the diameter of the inner shell-cavity, with three spirally contorted edges. From each spine arise at equal distances (equal to the half radius of the cavity) fifteen to twenty verticils of branches which increase in size from the base of the spine. Each verticil is composed of six forked branches (two from each spine-edge); the inferior are richly branched, and form by their connection the loose network of the spongy cortical shell, the surface of which is covered with numerous bent threads. Each spine bears a resemblance to a pine tree.

Dimensions.—Diameter of the spongy shell 0.3, of its inner cavity 0.15, of the central cube 0.02; length of the spines 0.5 to 0.6, breadth 0.01.

Habitat.—Central Pacific, Station 272, surface.

4. Octodendron araucaria, n. sp.

Radial spines eight, three-sided prismatic, with three spirally contorted edges, eight to ten times as long as the diameter of the inner shell-cavity (the free distal portion twice to three times as long). From each spine arise at equal distances thirty to thirty-five verticils of branches, which decrease in size towards the distal end. Each verticil is composed of six forked branches (two from each spine-edge); the inferior are richly ramified and form by their connection the loose spongy framework; the distal branches bear on the free end elegant spathillæ (as in the following species). Surface covered with innumerable straight bristles, as long as the cavity radius, and ending with a spathilla. Diameter of the central capsule about equal to the radius of the spongy sphere, its membrane is double-edged.

Dimensions.—Diameter of the spongy shell 1.4 mm., of its inner cavity 0.14, of the central cube 0.02, of the central capsule 0.5 to 0.6; length of the spines 0.9 to 1.2, breadth 0.02.

Habitat.—South Pacific, Station 288, surface.

5. Octodendron spathillatum, n. sp. (Pl. 18, figs. 2, 4).

Radial spines eight, three-sided prismatic, with contorted edges, five to eight times as long as the diameter of the shell-cavity (the free part twice as long). From each spine arise ten to twelve verticils of lateral branches; each verticil composed of three forked branches. The proximal larger branches ramify richly, and form by their connection the loose spongy framework of the spherical shell; the distal smaller branches are simple or bifurcated, and the ramules are provided with an elegant spathillum at the end (fig. 4). Entire surface of the spongy sphere covered with innumerable bristle-shaped radial spines (half as long as the cavity radius), zig-zag, bent, with beards, and with a spathillum at the end.

Dimensions.—Diameter of the spongy sphere 1 mm., of its central cavity 0.15, of the central cube 0.02; length of the spines 1 to 1.2 mm., breadth 0.008.

Habitat.—Central Pacific, Station 271, surface.

Subgenus 2. Octodendronium, Haeckel.

Definition.—Radial spines thirty-two or more, eight primary (arising from the eight corners of the central cube) and twenty-four or more secondary (between them).

6. Octodendron verticillatum, n. sp.

Radial spines thirty-two, with three denticulate straight edges, six to eight times as long as the diameter of the shell-cavity; the distal parts half free. Eight primary spines arise from the eight corners of the central cube, twenty-four secondary from the edges of these (a verticil of every three from each primary spine). Distal free parts of all thirty-two spines equal. Each spine with eight to ten verticils of forked lateral branches, without spathillæ. Surface of the spongy sphere covered with short simple bristles.

Dimensions.—Diameter of the spongy shell 0.3, of its cavity 0.12, of the central cube 0.02; length of the spines 0.7 to 1 mm., breadth 0.02.

Habitat.—South Pacific, Station 291, surface.

7. Octodendron contortum, n. sp.

Radial spines thirty-two, disposed in a similar manner to those of the former species (eight primary and twenty-four secondary); also the spongy shell of the same shape. The difference arises in the form of the spines, the three edges of which are much broader and spirally contorted around the axis; and thus the corresponding branches of the verticil do not lie in the same meridian-plane, but alternate one with another.

Dimensions.—Diameter of the spongy shell 0.4, of its cavity 0.1, of the central cube 0.02; length of the spines 0.8 to 1.2, breadth 0.04.

Habitat.—Central Pacific, Station 274, surface.

8. Octodendron arboretum, n. sp.

Radial spines sixty to ninety, three-sided prismatic, with spirally contorted and denticulate edges, six to eight times as long as the diameter of the inner shell-cavity. Eight primary arise from the eight corners of the central cube, twenty-four others from their three edges (as in the two former species); the remaining thirty to sixty spines seem to arise between the former and immediately from the dense spongy framework, which is twice as thick as the diameter of the inner shell-cavity. The numerous verticils of the free distal part are of equal shape in all the spines, composed of three forked branches in the terminal, and of more ramified branches in the inferior parts. Entire surface of the spongy shell covered with simple radial bristles, without spathillæ.

Dimensions.—Diameter of the spongy shell 0.75, of its central cavity 0.15, of the central cube 0.02; length of the spines 0.9 to 1.2, breadth 0.02.

Habitat.—Tropical Pacific, Station 225, surface.

Genus 120. Spongosphæra,^[159] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Astrosphærida with two concentric latticed medullary shells, connected by radial beams; the outer is immediately enveloped by the spongy framework, and bears numerous radial spines.

The genus Spongosphæra (in the definition here restricted) differs from Spongopila in the double medullary shell, which in the latter is simple; it exhibits to the latter the same relation that Spongodictyon among the Liosphærida bears to Spongoplegma. The outer medullary shell of Spongosphæra is immediately enveloped by the spongy wicker-work, which everywhere pierces the wall of the central capsule.

1. Spongosphæra streptacantha, Haeckel.

Spongosphæra streptacantha, Haeckel, 1862, Monogr. d. Radiol., p. 455, Taf. xxvi. figs. 1-3.

Spongy shell of polyhedric, irregular outline, the framework being prolonged sheath-like into the eight to twelve radial spines, which are quite irregularly distributed, very large, three-sided prismatic, with three serrated, spirally contorted edges; their length is twice to four times as great as the diameter of the spongy body; they arise with thinner bases from the outer medullary shell, which is three times as broad as the inner, both having roundish pores, twice to four times as broad as the bars; surface without radial by-spines.

Dimensions.—Diameter of the spongy shell 0.2 to 0.6, outer medullary shell 0.04 to 0.06, inner 0.012 to 0.016.

Habitat.—Cosmopolitan; common in all warmer seas, surface.

2. Spongosphæra polyacantha, J. Müller.

Spongosphæra polyacantha, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 32, Taf. iv. figs. 1-4.

Spongy shell spherical, with ten to twenty large radial spines, which arise with thinner bases from the medullary shell, and are prominent on the surface at different lengths; they are three-sided prismatic (not four-sided), with three leaf-shaped straight edges. Whilst the spongy framework is much looser than in the preceding species, both medullary shells have nearly the same shape.

Dimensions.—Diameter of the spongy shell 0.2 to 0.5, outer medullary shell 0.04 to 0.06, inner 0.012 to 0.016.

Habitat.—Mediterranean (Nice); Atlantic, Station 353, surface.

Subgenus Spongosphæromma, Haeckel.

Definition.—Radial spines on the surface of the spongy shell of two different kinds; large piercing main spines and small superficial by-spines.

3. Spongosphæra helioides, Haeckel.

Spongosphæra helioides, Haeckel, 1862, Monogr. d. Radiol., p.456, Taf. xii. figs. 11-13.

Spongy shell spherical, with numerous curved, bristle-shaped by-spines on the surface, as long as the radius. Main spines ten to twenty, irregularly disposed, prismatic, with three dentated, spirally contorted edges, broader toward the distal end. Outer medullary shell three times as broad as the inner, with polygonal meshes (of the same size as those in the spongy framework) and fine bars.

Dimensions.—Diameter of the spongy shell 0.2, outer medullary shell 0.02, inner 0.007.

Habitat.—Mediterranean (Messina).

4. Spongosphæra quadricuspis, n. sp.

Spongy shell spherical, with numerous curved, bristle-shaped by-spines on the surface, half as long as the radius. Main spines twenty to thirty, irregularly disposed, prismatic, with three dentated, spirally contorted edges, and at the distal end four strong pyramidal divergent teeth (three as terminations of the edges, the fourth as end of the spine axis). Outer medullary shell twice as broad as the inner, both having circular, regular pores, twice to three times as broad as the bars.

Dimensions.—Diameter of the spongy shell 0.3, outer medullary shell 0.04, inner 0.013.

Habitat.—Central Pacific, Station 272, surface.

Genus 121. Rhizosphæra,^[160] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 840.

Definition.—Astrosphærida with two concentric latticed medullary shells, connected by radial beams; from the outer arise numerous radial spines, which at equal distances are connected by a latticed spherical cortical shell, surrounded by a spongy framework.

The genus Rhizosphæra exhibits the same relation to Spongosphæra that Rhizoplegma bears to Spongopila; but in the latter the latticed medullary shell is simple, in the two former double. The wall of the central capsule is pierced only by the radial spines connecting the medullary and the cortical shells.

1. Rhizosphæra trigonacantha, Haeckel.

Rhizosphæra trigonacantha, Haeckel, 1862, Monogr. d. Radiol., p. 452, Taf. xxv. figs. 1-7.

Central cavity of the spongy cortical shell twice as broad as the diameter of the outer medullary shell. Bars of all three shells of the same breadth as the thirty to fifty (or more) radial spines, which are three-sided prismatic; their outer free distal end only as long as the diameter of the inner medullary shell.

Dimensions.—Diameter of the spongy shell 0.25, of its inner cavity 0.2, outer medullary shell 0.1, inner 0.05.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface from many Stations.

2. Rhizosphæra serrata, n. sp. (Pl. 18, figs. 5-7).

Central cavity of the spongy shell five times as broad as the diameter of the outer medullary shell. Bars of all three shells of the same breadth as the forty to sixty (or more) thin radial beams between them. These are three-sided prismatic, with denticulate edges, scarcely half as broad as their outer prolongations, which are half as long as the shell radius, and possess three spirally contorted serrated edges. (The figured specimen is a young one; in the older specimens the spongy framework of the cortical shell is much more developed.)

Dimensions.—Diameter of the spongy shell 0.3, of its central cavity 0.22, outer medullary shell 0.06, inner 0.02.

Habitat.—Central Pacific, Stations 270 to 274, surface.

3. Rhizosphæra leptomita, Haeckel.

Rhizosphæra leptomita, Haeckel, 1862, Monogr. d. Radiol., p. 453, Taf. xxv. figs. 8-10.

Central cavity of the spongy cortical shell twice as broad as the diameter of the outer medullary shell; bars of both very thin, only one-third as broad as the bars of the inner medullary shell. Radial spines thirty to fifty (or more), curved, three-sided prismatic; inside the spongy shell as thin as their bars, outside three times as broad.

Dimensions.—Diameter of the spongy shell 0.27, of its inner cavity 0.2, outer medullary shell 0.1, inner 0.05.

Habitat.—Mediterranean (Messina); Atlantic, Stations 348 to 354, surface.

Suborder PRUNOIDEA, Haeckel, 1883 (Pls. 13-17, 39, 40).

Definition.—Spumellaria with an ellipsoidal or cylindrical central capsule, prolonged into one axis (sometimes articulate by annular transverse strictures); with an ellipsoidal or cylindrical, fenestrated siliceous shell (often articulate by annular strictures), invariably prolonged into one axis. Fundamental form monaxon, usually with the poles of the prolonged dimensive main axis equal.

The suborder Prunoidea comprises those Spumellaria in which the fenestrated spherical shell appears prolonged into one axis. The geometric fundamental form of the shell, which in the Sphæroidea was a sphere, in this case therefore becomes an ellipsoid, and whilst in the former all axes originally have the same value (Homaxonia), here one main axis is constantly larger than all other axes (Monaxonia). Usually both poles of this main axis are equal (Haplopola); but in some genera both poles become different (Diplopola).

In the Sphæroidea all planes going through the centre of the shell are circular, whereas in the Prunoidea only those planes are circular which are perpendicular to the main axis; all other planes going through the centre are elliptical; the largest of these are the meridian planes, in which is situated the main axis. Commonly all meridian planes are equal, as no transverse axes (or cross axes) are differentiated.

In my Monograph (1862) only very few forms of Prunoidea, such as Didymocyrtis and Spongurus, are described, and the greater part of them are distributed under different genera of Sphæroidea, such as Haliomma and Actinomma. In my Prodromus (1881) I separated them as the family Zygartida (p. 462). But it seems now much more convenient to restrict this term to a particular family and to give a wider extension to the whole suborder under the name Prunoidea (called after the characteristic ellipsoidal form of a plum, or Prunus, with its stone).

The suborder Prunoidea comprises seven different families, of which the Ellipsida constitutes the simplest and the probable common ancestral group. In all Ellipsida the fenestrated shell is simple, and never composed of concentric or twin shells. In their primitive genus Cenellipsis, the whole shell is geometrically nothing more than a simple ellipsoid (Pl. 39, figs. 1, 2). By development of radial spines it passes into Ellipsidium, by development of spongy framework into Spongellipsis. In the greater part of this family large spines are developed on both poles of the main axis of the shell, but sometimes instead of these solid spines, two opposite hollow fenestrated tubes are developed (Pipettella, Pl. 39, fig. 6).

The second family of Prunoidea, the Druppulida, is much richer in different forms than the simple Ellipsida. In this case the ellipsoidal shell is composed of two or three (rarely more) concentric shells. Constantly one or two of these fenestrated shells are enclosed in the central capsule, and may therefore be called "medullary shells"; and one or two (rarely more) lie outside the central capsule, "cortical shells." The inner medullary shells (one or two) are either spherical or ellipsoidal; the outer cortical shells (one or two, rarely more) are always ellipsoidal. All concentric shells are connected by radial beams. In the simplest form of the subfamily, Druppula (Pl. 39, fig. 3), one medullary shell is connected with one cortical shell. By duplication of the medullary shell arises Prunulum (Pl. 39, fig. 4), and by duplication or multiplication of the cortical shell Cromyodruppa (Pl. 15, figs. 1-4) is formed. In by far the greater portion of this subfamily large spines are developed on both poles of the main axis of the cortical shell (Pls. 16, 17), but sometimes also instead of these solid spines two opposite hollow fenestrated tubes are developed (Pipetta, Pl. 39, figs. 7, 8).

A third family of Prunoidea, closely allied to the two preceding families, is the Spongurida, in which we include all Prunoidea with an ellipsoidal or cylindrical, unjointed shell, in which the lattice-work of the cortical shell is transformed into an irregular, siliceous framework. In the simplest form, Spongellipsis, the simple lattice-shell of Cenellipsis is substituted by an external spongy envelope. In other cases (Spongurus and allied genera) the whole cavity of this external spongy shell is distended with a fine spongy framework. The subfamily of Spongodruppida is distinguished by the possession of a simple or double latticed medullary shell; this lies in the midst of the central capsule, and is connected by radial beams (perforating its membrane) with the enveloping spongy cortical shell. The surface of the latter may bear either radial spines, or two opposite strong polar spines, at the poles of the main axis (Pl. 17, fig. 12).

Closely allied to the Ellipsida and Druppulida are two other families of the Prunoidea, the Artiscida and Cyphinida, which differ from the former by a circular constriction in the equatorial plane of the ellipsoidal shell; and in this way assume a characteristic twin form, like a figure of eight. In the Artiscida the shell is simple (as in the Ellipsida), whereas in the Cyphinida it is composed of two or more concentric shells (as in the Druppulida). The simplest form of the Artiscida is Artiscus (Pl. 39, fig. 9), differing from Cenellipsis in the ring-shaped, equatorial constriction. In other Artiscida polar appendages are developed on both poles of the main axis, either in the form of solid, strong spines (Stylartus), or hollow fenestrated tubes (Cannartus, Pl. 39, fig. 10).

The family Cyphinida differs from the Druppulida in the equatorial constriction of the shell, and from the Artiscida in the presence of two or more concentric shells. One or two of these concentric fenestrated shells are enclosed in the central capsule (and therefore may be called "medullary shells"); the others (one or two, rarely more) lie outside of the central capsule (therefore "cortical shells"). The internal "medullary shells" are always spherical or somewhat lenticular, compressed from both sides; the external "cortical shells" have constantly a ring-like constriction in the equatorial plane, and "twin-shells" are therefore like a figure of eight. The simplest form of this subfamily is Cyphanta, composed of a simple medullary shell and a simple cortical shell, the two being connected in the equatorial plane by radial beams. In Cyphonium (Pl. 39, fig. 12) the medullary shell is doubled, and in Cypassis (Pl. 39, fig. 13) the cortical shell likewise. On both poles of the main axis strong spines are often developed (Cyphinus, Pl. 39, fig. 14), or hollow fenestrated tubes (Cannartidium, Pl. 39, figs. 16-19).

The equatorial constriction of the ellipsoidal shell, which characterises the Artiscida and Cyphinida, is repeated or multiplied in the two following families, in the Panartida and Zygartida; in the former we find three ring-like strictures, in the latter five or more (lying in parallel transverse planes); therefore the fenestrated shell is composed in the one instance of four chambers, in the other of six or more; all the chambers form a single series and have a common main axis. All constrictions lie in planes parallel to the equatorial plane of the original ellipsoid; in the centre of the latter constantly lies a double "medullary shell," composed of two concentric, either spherical or lenticular, compressed shells. In all Panartida we call the two inner chambers (on both sides of the equatorial constriction) "proximal chambers," the two outer chambers (on the poles of the main axis) "distal chambers." The four-chambered cortical shell of the Panartida is either simple (in Panartus, Pl. 40, figs. 1-4) or double, with an external mantle (as in Peripanartus, Pl. 40, figs. 5-7). The simplest form of the subfamily is Panartus (loc. cit.). In this case also on both poles of the main axis may be developed solid spines, or hollow fenestrated tubes (Panarium, Pl. 40, fig. 9).

The seventh and last family of the Prunoidea, the Zygartida is most nearly allied to the Panartida, and appears as a further developmental step from that family. Whilst in the Panartida the cortical shell is constantly four-chambered, with three parallel ring-like constrictions, in the Zygartida it is always prolonged and composed of six or more chambers, separated by five or more ring-shaped constrictions, in the middle of which is the equatorial stricture. In the centre of the latter (as also in the Panartida) always lies the double medullary shell, composed of two concentric, spherical, or lenticular shells. The number of the chambers of the cortical shells is commonly six or eight (with five to seven ring strictures), but it often mounts to ten and sometimes to twenty (with nineteen strictures), as in some species of Zygartus (Pl. 40, fig. 13). All the chambers lie in one series, one behind another, with a common main axis. The cortical shell is usually simple (in Ommatocampe, Pl. 40, fig. 10), sometimes double (in Desmocampe, Pl. 40, fig. 12), rarely triple (in Zygocampe, Pl. 40, fig. 13). In all three cases hollow fenestrated tubes may be developed on the poles of the main axis.

The morphological references and the phylogenetic affinities of all Prunoidea are so complex, that they seem to represent a quite natural group; all forms of it may be derived from the common ancestral form Cenellipsis. But a far more difficult question is the manner in which its pedigree may be constructed. The oldest family is probably the simplest, namely, Ellipsida. From this the Druppulida may be derived by production of medullary shells, the Artiscida by equatorial constriction. The Cyphinida can be produced either from the Druppulida by equatorial constriction or from the Artiscida by development of medullary shells. The Panartida appear as further developmental steps of the Cyphinida, by duplication of the chamber number; and the Zygartida as further productions of the Panartida, by increasing the number of the chambers.

The seven subfamilies of the Prunoidea can be arranged in two sections according to the presence or absence of medullary shells. The Ellipsida, Spongellipsida, and Artiscida possess a simple cortical shell, without a medullary shell; they represent the section Cenoprunida. All other families possess medullary shells, and so represent the section Coccoprunida.

Another character, which can be employed in the arrangement of the seven subfamilies in some larger groups, is the presence or absence of ring-like constrictions, by which the cortical shell is divided into chambers. I. The Monoprunida comprise all forms without any constriction, of which the Ellipsida are without a medullary shell, the Druppulida with one or two medullary shells, and the Spongurida with a spongy cortical shell. II. The Dyoprunida contain all forms with a cortical twin shell, or with two chambers separated by one equatorial constriction, of which the Artiscida are without a medullary shell and the Cyphinida have one or two medullary shells. III. The Polyprunida comprise all forms with several (three or more) constrictions, which separate four or more chambers, of which the Panartida have three constrictions and four chambers, and the Zygartida five or more constrictions and six or more chambers.

The Central Capsule of the Prunoidea is originally ellipsoidal (monaxial), and preserves this form in the greater part of the genera. In some groups, where the axis of the ellipsoid is much prolonged, it passes over to the cylindrical form (with hemispherical vaultings on both poles), as in Spongurus and Spongocore, in many Panartida and Zygartida. Very often the ellipsoidal or cylindrical capsule gets annular transverse constrictions, corresponding to those of the enveloping cortical shell (one single, equatorial stricture in the Artiscida and Cyphinida, three strictures in the Panartida, five or more in the Zygartida). In the Cenoprunida (Ellipsida and Artiscida, also in Spongellipsis) the central capsule lies freely in the cavity of the cortical shell, separated from its inner surface by the jelly-envelope; in all other groups it contains a part of the skeleton, the medullary shell and the beams which connect it with the enveloping cortical shell.

Synopsis of the Families of Prunoidea.

A. MONOPRUNIDA. Shell without transverse stricture a. Shell simple, latticed (not spongy), without enclosed internal shells, 1. Ellipsida.

b. Shell composed of two or more concentric latticed shells (not spongy), 2. Druppulida.

c. Shell partially or wholly composed of an irregular spongy framework, 3. Spongurida.

B. DYOPRUNIDA. Shell bilocular, divided by an equatorial stricture into two communicating hemi-ellipsoidal shells. d. Shell simple, without enclosed internal shells, 4. Artiscida.

e. Shell composed of two or more concentric shells, 5. Cyphinida.

C. POLYPRUNIDA. Shell multilocular, divided by three or more parallel transverse strictures into four or more serial cameræ. f. Shell with three parallel strictures and therefore four cameræ, 6. Panartida.

g. Shell with five or more parallel strictures and therefore six or more cameræ, 7. Zygartida.

A. MONOPRUNIDA. Shell without transverse stricture

a. Shell simple, latticed (not spongy), without enclosed internal shells,

1. Ellipsida.

b. Shell composed of two or more concentric latticed shells (not spongy),

2. Druppulida.

c. Shell partially or wholly composed of an irregular spongy framework,

3. Spongurida.

B. DYOPRUNIDA. Shell bilocular, divided by an equatorial stricture into two communicating hemi-ellipsoidal shells.

d. Shell simple, without enclosed internal shells,

4. Artiscida.

e. Shell composed of two or more concentric shells,

5. Cyphinida.

C. POLYPRUNIDA. Shell multilocular, divided by three or more parallel transverse strictures into four or more serial cameræ.

f. Shell with three parallel strictures and therefore four cameræ,

6. Panartida.

g. Shell with five or more parallel strictures and therefore six or more cameræ,

7. Zygartida.

Family XI. Ellipsida, Haeckel, 1882 (Pls. 13, 14, 39).

Definition.—Prunoidea with simple ellipsoidal shell, without equatorial stricture (without enclosed medullary shell); network a simple lattice lamella, not spongy. Central capsule ellipsoidal or cylindrical, without annular equatorial constriction.

The family Ellipsida comprises the simplest forms of Prunoidea, and probably represents the ancestral forms of this whole suborder. The fenestrated shell, which encloses the ellipsoidal central capsule, is a perfectly simple "cortical shell" of the same form, without enclosed "medullary shell." Its form is commonly a regular monaxial ellipsoid; sometimes a little modified by unequal growth of the two poles of the main axis. Two opposite large spines are often developed at these poles, or it may be that instead of these, two hollow fenestrated tubes are present.

The ellipsoidal fenestrated shell exhibits in the regular Ellipsida all the characters of a geometric ellipsoid; one main axis surpasses in length all other possible axes. All sections going through this main axis are "meridian sections," with elliptical periphery; all sections perpendicular to the main axis are "transverse sections," with circular periphery. The largest of these is the equatorial section, which divides the main axis into halves. The diameter of this equatorial plane is the "minor axis" of the ellipsoid.

The proportion of the two axes of the ellipsoidal shell, of the major vertical or main axis and the minor horizontal or equatorial axis, is commonly between 6 : 5 and 3 : 2. In the former case it approaches the spherical shell, from which it is derived; in the latter case it becomes almost fusiform or cylindrical. The network of silex, constituting the shell, is constantly a simple latticed lamella, never composed of concentric shells (as in Druppulida) or spongy (as in Spongurida). The network is often very regular and elegant, in other cases irregular.

The simplest genus among the Ellipsida, and probably the common ancestral form of the whole subfamily, is the genus Cenellipsis, possessing a simple ellipsoidal shell without any appendages. It is derived from Cenosphæra (the simplest spherical shell) by the prolongation of one axis. Cenellipsis passes over into Ellipsidium by the production of radial spines on the surface (corresponding to Heliosphæra). Axellipsis is a peculiar genus differing from Cenellipsis in an axial rod, which corresponds to the minor or equatorial axis. In all other genera of the subfamily both poles of the main axis are distinguished by peculiar polar prolongations, either hollow fenestrated tubes (as in Pipettella) or strong solid spines. Both polar spines are of equal size and similar form in Ellipsoxiphus, unequal in Ellipsostylus. From the latter is derived Lithapium, by reduction and loss of one spine (so that only one remains); Lithomespilus, by production of a bunch of several spines at one pole. In the three latter genera both poles of the main axis are unequal, in all others equal.

The central capsule of the Ellipsida is in all cases ellipsoidal, and occupies the largest part of the shell, being separated from its inner surface by a thinner or thicker jelly-mantle.

Synopsis of the Genera of Ellipsida.

Ellipsoidal shell without polar appendages (neither solid spines nor hollow tubes at the poles of the axis). Surface without radial spines. Shell cavity simple, without an axial rod, 122. Cenellipsis.

Shell cavity with a transverse axial rod, 123. Axellipsis.

Surface covered with radial spines, 124. Ellipsidium.

Ellipsoidal shell with polar appendages (either solid spines or hollow fenestrated tubes) at the poles of the main axis. Solid spines of similar shape, at both poles of the main axis. Shell cavity simple, without axial rods, 125. Ellipsoxiphus.

Shell cavity with a cross of axial rods, 126. Axoprunum.

Solid spines of different shape, at both poles of the main axis. Two polar spines of different shape, 127. Ellipsostylus.

A bunch of spines at one pole only, 128. Lithomespilus

Only a single spine at one one pole, 129. Lithapium.

Two hollow fenestrated tubes opposite, at the poles of the main axis, 130. Pipettella.

Ellipsoidal shell without polar appendages (neither solid spines nor hollow tubes at the poles of the axis).

Surface without radial spines.

Shell cavity simple, without an axial rod,

122. Cenellipsis.

Shell cavity with a transverse axial rod,

123. Axellipsis.

Surface covered with radial spines,

124. Ellipsidium.

Ellipsoidal shell with polar appendages (either solid spines or hollow fenestrated tubes) at the poles of the main axis.

Solid spines of similar shape, at both poles of the main axis.

Shell cavity simple, without axial rods,

125. Ellipsoxiphus.

Shell cavity with a cross of axial rods,

126. Axoprunum.

Solid spines of different shape, at both poles of the main axis.

Two polar spines of different shape,

127. Ellipsostylus.

A bunch of spines at one pole only,

128. Lithomespilus

Only a single spine at one one pole,

129. Lithapium.

Two hollow fenestrated tubes opposite, at the poles of the main axis,

130. Pipettella.

Genus 122. Cenellipsis,^[161] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, without radial spines and without polar tubes.

The genus Cenellipsis is the simplest and most primitive form, not only among the Ellipsida, but also among the Prunoidea, and it may therefore be regarded as the common ancestral form of the whole family. It corresponds to Cenosphæra among the Sphæroidea, to Cenodiscus among the Discoidea, to Cenolarcus among the Larcoidea. Probably it is derived from Cenosphæra by prolongation of one axis.

Subgenus 1. Cenellipsium, Haeckel.

Definition.—Network of the shell regular, with meshes of equal size and similar form.

1. Cenellipsis primitiva, n. sp.

Proportion of the longer axis of the ellipsoid to the shorter = 3 : 2. Network of the thin wall very delicate and regular, with hexagonal pores. All pores of nearly the same size and form, ten to twelve times as broad as the bars; nine to twelve on the half equator of the shell. Surface smooth.

Dimensions.—Longer axis of the ellipsoid 0.09 to 0.11, shorter axis 0.06 to 0.08; pores 0.01, bars between them 0.001.

Habitat.—Pacific, central area, Station 272, surface.

2. Cenellipsis faceta, n. sp. (Pl. 39, fig. 1).

Proportion of the longer axis of the ellipsoid to the shorter = 4 : 3. Network of the thin wall delicate and regular. All the pores of the same size and form, circular, with a hexagonal frame, twice to three times as broad as the bars; eight to ten on the half equator. Surface smooth or slightly spiny.

Dimensions.—Longer axis of the ellipsoid 0.12 to 0.13, shorter axis 0.09 to 0.1; pores 0.013, bars 0.005.

Habitat.—Pacific, central area. Station 274, surface.

3. Cenellipsis ehrenbergii, Haeckel.

Haliomma (?) cenosphæra, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf xxvi. fig. 5.

Proportion of the longer axis to the shorter = 2 : 1. Network of the thin wall regular or subregular. All pores circular, nearly of the same size, without hexagonal frame, three to four times as broad as the bars; eight to nine on the half equator. Surface covered with small thorns.

Dimensions.—Longer axis of the ellipsoid 0.16 to 0.2, shorter axis 0.08 to 0.1; pores 0.1, bars 0.003.

Habitat.—Fossil in the Tertiary rocks of Barbados (Ehrenberg, Haeckel).

4. Cenellipsis circopora, n. sp.

Proportion of the longer axis to the shorter = 5 : 3. Network of the thin wall delicate and regular. All pores circular, nearly of the same size, without hexagonal frame, twice as broad as the bars; fifteen to twenty on the half equator. Surface quite smooth.

Dimensions.—Longer axis of the ellipsoid 0.15 to 0.2, shorter axis 0.09 to 0.12; pores 0.08, bars 0.4.

Habitat.—North Pacific, Station 236, surface.

5. Cenellipsis micropora, n. sp.

Proportion of the longer axis to the shorter = 5 : 4. Network of the thick wall quite regular. All pores circular, without hexagonal frame, very small, scarcely half as broad as the bars; six to eight on the half equator. Surface quite smooth.

Dimensions.—Longer axis of the ellipsoid 0.1, shorter axis 0.08; pores 0.004, bars 0.01.

Habitat.—South Pacific, Station 289, surface.

Subgenus 2. Cenellipsula, Haeckel.

Definition.—Network of the shell irregular, with meshes of different size or form.

6. Cenellipsis heteropora, n. sp.

Proportion of the longer axis to the shorter = 3 : 2 or = 5 : 3. Network of the thin wall very irregular, with polygonal meshes of different size and form (for the most part pentagonal or hexagonal, but also many tetragonal or heptagonal). The largest pores four to six times as broad as the smallest; ten to twenty pores on the half equator; bars between them thin. Surface smooth or somewhat spiny.

Dimensions.—Longer axis of the ellipsoid 0.18 to 0.22, shorter axis 0.1 to 0.12; pores 0.004 to 0.008, bars 0.001.

Habitat.—Indian Ocean, near the Cocos Islands, surface, Rabbe.

7. Cenellipsis maxima, n. sp.

Proportion of the longer axis to the shorter = 3 : 2. Network of the thin wall very irregular, with polygonal meshes of very different size and form, twice to eight times as broad as the bars; fifty to sixty on the half equator. Surface smooth.

Dimensions.—Longer axis of the ellipsoid 0.36, shorter axis 0.25; pores 0.004 to 0.015, bars 0.002.

Habitat.—Equatorial Atlantic, Station 347, surface.

8. Cenellipsis ovulum, n. sp.

Proportion of the longer axis to the shorter = 3 : 2. Network of the thin wall very irregular, with roundish or longish pores of very different size and form. Pores flat, with even margins, thirty to forty on the half equator, twice to six times as broad as the bars. Surface smooth. (This species being observed alive, showed a transparent central capsule of ellipsoidal form, two-thirds as large as the shell.)

Dimensions.—Longer axis of the ellipsoid 0.3, shorter axis 0.2; pores 0.04 to 0.012, bars 0.002.

Habitat.—Indian Ocean, Ceylon, Haeckel; Pacific, central area, Station 266, surface.

9. Cenellipsis infundibulum, n. sp. (Pl. 39, fig. 2).

Proportion of the longer axis to the shorter = 3 : 2. Network of the thick wall irregular, with roundish pores of different size and form. Pores funnel-like, with prominent, irregular, spiny crests between them, their outer aperture three to four times as broad as the inner; twelve to fifteen pores on the half equator. Surface prickly.

Dimensions.—Longer axis of the ellipsoid 0.14, shorter axis 0.11; outer aperture of the pores 0.01 to 0.012, inner aperture 0.003 to 0.004.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

10. Cenellipsis oblonga, n. sp.

Proportion of the longer axis to the shorter = 2 : 1. Network of the thick wall irregular, with roundish pores of different size and form. Pores with prominent conical edges, about as broad as the bars; twenty to twenty-five on the half equator. Sometimes each pore is prolonged into a short conical tubulus.

Dimensions.—Longer axis of the ellipsoid 0.22, shorter axis 0.12; pores and bars 0.008 to 0.012.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

Genus 123. Axellipsis,^[162] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, without radial spines or polar tubes, but with an inner transverse axial rod, which corresponds to the shorter axis of the ellipsoid.

The genus Axellipsis differs from the simple Cenellipsis in a very peculiar character, namely, the presence of an inner siliceous bar marking the minor axis of the ellipsoidal shell. If in some forms of Druppula (e.g., Pl. 39, fig. 3) we remove the central medullary shell and prolong both beams (connecting it with the cortical shell) till they unite in the centre, we shall arrive at Axellipsis. Therefore Axellipsis may be derived in the same way from Druppula as Axoprunum is from Lithatractus, by phyletic loss of the medullary shell.

1. Axellipsis perforata, n. sp.

Proportion of the major axis of the ellipsoid to the minor = 3 : 2. Pores of the shell regular, circular, twice as broad as the bars; ten to twelve on the half equator. Surface smooth.

Dimensions.—Longer axis of the shell 0.12, shorter axis 0.08; pores 0.006, bars 0.003.

Habitat.—Central area of the Pacific, Station 266, depth 2750 fathoms.

2. Axellipsis lobata, n. sp.

Proportion of the major axis to the minor = 5 : 4. Meshes of the shell irregular, roundish, lobed, with three to six indentations (each mesh formed by the confluence of three to six, commonly four or five, smaller pores); eight to nine meshes on the half equator, these being twice to four times as broad as the bars.

Dimensions.—Longer axis of the shell 0.1, shorter axis 0.08; pores 0.007 to 0.01, bars 0.003.

Habitat.—Tropical zone of the Western Pacific, Station 225, surface.

Genus 124. Ellipsidium,^[163] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, with numerous radial spines on the surface, without polar spines or tubes.

The genus Ellipsidium differs from Cenellipsis solely in the development of numerous radial spines on the surface, and exhibits the same phylogenetic relation to it that Heliosphæra bears to Cenosphæra.

1. Ellipsidium pandanidium, n. sp.

Proportion of the longer axis of the ellipsoid to the shorter = 5 : 4. Shell thick walled, with regular and hexagonal meshes, twice as broad as the bars; eighteen to twenty on the half equator. In each hexagon-corner (between three pores) arises a short, three-sided pyramidal spine, half as long as the equatorial radius, and as thick at the base as a single mesh.

Dimensions.—Major axis of the ellipsoid 0.15, minor 0.12; pores 0.006, bars 0.003; length of the radial spines 0.03, basal breadth 0.006.

Habitat.—Fossil in the Tertiary rocks of Barbados (Haeckel).

2. Ellipsidium datura, n. sp.

Proportion of the longer axis of the ellipsoid to the shorter = 4 : 3. Shell thick walled, with regular, circular meshes, twice as broad as the thick bars between them eight to ten meshes on the half equator. Outer surface of the shell thorny, covered with short, conical, radial spines, which are regularly distributed (one spine between every three meshes), and about as long as the diameter of the meshes. (The shell is similar to the outer shell of Haliomma castanea, Haeckel, Monogr. d. Radiol., Taf. xxiv. fig. 4.)

Dimensions.—Major axis of the ellipsoid 0.12, minor axis 0.09; meshes 0.012, bars 0.006.

Habitat.—Western part of the Tropical Pacific, Station 225, depth 4475 fathoms.

3. Ellipsidium artocarpus, n. sp.

Proportion of the longer axis to the shorter = 3 : 2. Shell thick walled, with regular, circular meshes, separated by deep furrows, which represent a regular, hexagonal framework; on the half equator twelve to fifteen meshes, scarcely broader than the broad bars between them. Outer surface spiny; between every three meshes arises a strong radial spine, twice to three times as long as the diameter of the meshes; the base of the spine is like a three-sided pyramid.

Dimensions.—Major axis of the ellipsoid 0.12, minor axis 0.08; meshes 0.006, bars 0.005.

Habitat.—Central area of the Pacific, Station 268, depth 2900 fathoms.

4. Ellipsidium opuntia, n. sp.

Proportion of the longer axis to the shorter = 5 : 4. Shell thin walled, with irregular, roundish meshes of different size and form, about twice to three times as broad as the irregular, thin bars between them; ten to fifteen meshes on the half equator. Between the meshes arise numerous thin, bristle-like, radial spines, about as long as the shorter radius of the shell. The number of the meshes may be three to four times as great as the number of the spines.

Dimensions.—Major axis of the ellipsoid 0.15, minor axis 0.12; pores 0.006 to 0.01, bars 0.003 to 0.004.

Habitat.—Southern Pacific, Station 284, surface.

5. Ellipsidium echinidium, n. sp.

Proportion of the longer axis to the shorter = 4 : 3. Shell thick walled, with irregular, roundish pores of different size and form, about as large or somewhat smaller than the broad bars; twelve to sixteen pores on the half equator. On the surface, irregularly scattered, twenty to thirty strong, three-sided pyramidal, radial spines, one-fourth to one-half as long as the main axis.

Dimensions.—Major axis of the ellipsoid 0.16, minor 0.12; pores and bars 0.002 to 0.008; length of the radial spines 0.04 to 0.08, basal breadth 0.01.

Habitat.—Equatorial Atlantic, Station 347, depth 2250 fathoms.

Genus 125. Ellipsoxiphus,^[164] Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, vol. xlv. p. 25.

Definition.—Ellipsida with simple ellipsoidal shell, the main axis of which is prolonged at both poles into two strong opposite spines of equal size and similar form.

The genus Ellipsoxiphus was established by Dunikowski (in 1882, loc. cit.) for those simple amphistylous fenestrated shells, formerly united with Xiphosphæra, in which the mathematical form of the shell itself is not a true sphere, but an ellipsoid. It may therefore be derived from Xiphosphæra by prolongation of the axis in which lie both polar spines; but it may also be derived from Cenellipsis by the production of two equal spines at the poles of the main axis.

Subgenus 1. Ellipsoxiphetta, Haeckel.

Definition.—Network of the shell regular, with pores of equal size and similar form.

1. Ellipsoxiphus elegans, n. sp. (Pl. 14, fig. 7).

Proportion of the major axis of the ellipsoid to the minor = 5 : 4. Shell thick walled, with regular, circular meshes, separated by a regular, hexagonal elevated framework. From each hexagon-corner arises (between every three meshes) a short thin spine, about as long as the diameter of a mesh; twelve to fourteen meshes on the half equator, of the same breadth as the bars. Polar spines three-sided prismatic, cuspidate, about as long as the axis of the shell. (This elegant and not uncommon species is remarkable for its variations. By unequal development of both spines it passes over to Ellipsostylus.) In the figured variety (Pl. 14, fig. 7) the ends of the surface spines are connected by a very delicate network, so as to form an outer veil. This may further be separated as a peculiar genus Ellipsoxiphium palliatum.

Dimensions.—Longer axis 0.08 to 0.13, shorter axis 0.06 to 0.11; pores and bars 0.008; length of the polar spines 0.06 to 0.12, basal breadth 0.01.

Habitat.—Pacific, central area, Stations 270 to 274, from 2350 to 2925 fathoms.

2. Ellipsoxiphus flosculus, n. sp.

Proportion of the major axis to the minor = 6 : 5. Shell very thick walled, with regular, hexagonal meshes, eight to nine on the half equator, three to four times as broad as the bars. The inner contour of the meshes is circular, the outer six-lobed (similar to Xiphostylus phasianus, Pl. 13, fig. 9). Polar spines three-sided pyramidal, about as long as the major axis of the shell; their basal thickness equals one mesh.

Dimensions.—Longer axis 0.12, shorter axis 0.1; pores 0.012 to 0.015, bars 0.004; length of the polar spines 0.12 to 0.15, basal breadth 0.015.

Habitat.—Fossil in the Tertiary rocks of Barbados (Teuscher).

3. Ellipsoxiphus fragilis, n. sp.

Proportion of the major axis to the minor = 4 : 3. Shell thin walled, with regular, circular meshes, twice as broad as the bars; ten to twelve on the half equator. Surface smooth. Polar spines cylindrical, at the apex conical, half as long as the major axis.

Dimensions.—Longer axis 0.16, shorter axis 0.12; pores 0.008, bars 0.004; length of the polar spines 0.09, basal breadth 0.008.

Habitat.—South Atlantic, Station 325, surface.

Subgenus 2. Ellipsoxiphilla, Haeckel.

Definition.—Network of the shell irregular, with pores of different size or form.

4. Ellipsoxiphus claviger, n. sp. (Pl. 14, fig. 3).

Xiphosphæra clavigera, Haeckel, 1881, Prodromus et Atlas.

Proportion of the major axis to the minor = 5 : 4. Shell thick walled, with irregular network; meshes roundish or circular, double contoured, of unequal size, twice to four times as broad as the bars; eight to ten on the half equator. Polar spines club-shaped, with prominent edges, about as long as the minor axis; thicker in their middle part than at both ends (differs from Xiphosphæra clavigera by the ellipsoidal form of the shell, and the double length of the spines).

Dimensions.—Longer axis 0.15. shorter axis 0.12; pores 0.007 to 0.015, bars 0.004; length of the polar spines 0.12, thickness in the middle part 0.02.

Habitat.—Central area of the Pacific, Station 272, depth 2600 fathoms.

5. Ellipsoxiphus suessi, Dunikowski.

Ellipsoxiphus suessi, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. xlv. p. 26, Taf. v. fig. 50.

Proportion of the major axis to the minor = 7 : 5. Shell thick walled, with irregular, roundish meshes, six to eight on the half equator, twice to three times as broad as the bars. Polar spines nearly cylindrical, blunt, as long as the major axis.

Dimensions.—Longer axis 0.14; shorter axis 0.1; pores 0.018 to 0.023, bars 0.01; length of the polar spines 0.12; thickness of them 0.035.

Habitat.—Fossil in the Alpine Lias, Schafberg near Salzburg, Dunikowski.

6. Ellipsoxiphus parvoforaminus, Dunikowski.

Ellipsoxiphus parvoforaminus, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. xlv. p. 26, Taf. v. fig. 51.

Proportion of the major axis to the minor = 7 : 6. Shell thick walled, with irregular, roundish or oval meshes, ten to twelve on the half equator, scarcely as broad as the bars. Polar spines conical, shorter than the minor axis.

Dimensions.—Longer axis 0.14, shorter axis 0.12; pores 0.016 to 0.01, bars 0.01 to 0.02; length of the polar spines 0.1, basal thickness 0.045.

Habitat.—Fossil in the Alpine Lias, Schafberg near Salzburg, Dunikowski.

7. Ellipsoxiphus bipolaris, n. sp. (Pl. 14, fig. 11).

Xiphosphæra bipolaris, 1881, Prodromus et Atlas.

Proportion of the major axis to the minor = 8 : 7. Shell thick walled, with irregular, roundish meshes, twice to three times as broad as the bars; sixteen to twenty on the half equator. Polar spines short and thick, three-sided pyramidal, scarcely half as long as the shorter radius of the shell; surrounding the base of every spine is a circle of eight to nine shorter spines.

Dimensions.—Longer axis 0.08, shorter axis 0.07; pores 0.003 to 0.007, bars 0.002; length of the polar spines 0.02 to 0.03, basal thickness 0.02.

Habitat.—Tropical part of the Western Pacific, Station 225, depth 4475 fathoms.

8. Ellipsoxiphus atractus, n. sp. (Pl. 14, fig. 1).

Proportion of the major axis to the minor = 3 : 2. Shell spindle-shaped, very thick walled, with roundish, very irregular meshes, twice to five times as broad as the bars; eight to twelve on the half equator. The meshes are partly simple, oblong, partly lobed or composed of two to four (commonly three) confluent meshes. Surface smooth. Polar spines very short and thick, shorter than the minor radius of the shell, three-sided pyramidal, with prominent, somewhat contorted edges.

Dimensions.—Longer axis 0.15, shorter axis 0.1; meshes 0.007 to 0.02, bars 0.004; length of the polar spines 0.04, basal thickness 0.03.

Habitat.—Central area of the Pacific, Station 268, depth 2900 fathoms.

Genus 126. Axoprunum,^[165] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, the main axis of which is prolonged at both poles into two opposite spines of equal size and similar form. Within the cavity of the shell four radial rods arise from its inner surface, two in the main axis, two in the smallest axis, perpendicular to the former; their free inner ends are at the same distance from the centre.

The genus Axoprunum possesses precisely the same shell as the foregoing Ellipsoxiphus, but differs from it in a very remarkable peculiarity. The two polar spines are centripetally prolonged into two internal beams, and perpendicular to these are two other, opposite, transverse beams, marking the minor axis of the ellipsoid. The free inner ends of all four radial rods bear little thickened knobs, and are at the same distance from the centre. It therefore appears as though a central, spherical, medullary shell had been lost, and this gives a strong support to the important hypothesis, that in many Sphærellaria, where the medullary shell is absent, it may have been lost by phylogenetic reduction or retrograde metamorphosis. In this case Axoprunum (and Ellipsoxiphus) would arise from Lithatractus.

1. Axoprunum stauraxonium, n. sp. (Pl. 48, fig. 4).

Shell ellipsoidal, one and one-third times as long as broad, with smooth surface. Network regular, with circular meshes four times as broad as the bars. Two polar spines three-sided pyramidal, half as long as the shell, as thick at the base as a single mesh. Four inner radial beams (lying, two in the major and two in the minor axis of the ellipsoid) very thin, at the central free ends knob-like, thickened. The distance between two opposite beams equals one-third of the minor axis, and indicates probably the diameter of the lost spherical medullary shell. (Three perfect and complete specimens of the same size and shape were observed.)

Dimensions.—Major axis of the ellipsoid 0.14, minor axis 0.11; pores 0.012, bars 0.003; length of the polar spines 0.07, basal breadth 0.012. (Diameter of the lost medullary shell 0.03?)

Habitat.—South Atlantic, Station 338, depth 1990 fathoms.

Genus 127. Ellipsostylus,^[166] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, the main axis of which is prolonged at both poles into two opposite spines of different size or form.

The genus Ellipsostylus differs from Ellipsoxiphus only in the unequal size or different form of the polar spines, which in the former are equal. This difference does not seem important at first, but in the further development it produces very singular and strange forms. Theoretically it is always important, because the fundamental haplopolar form of the monaxon body becomes diplopolar by this differentiation.

Subgenus 1. Ellipsostyletta, Haeckel.

Definition.—Network of the shell regular, with pores of equal size and similar form.

1. Ellipsostylus ornithoides, n. sp.

Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Shell thin walled, with regular, circular meshes and hexagonal framework between them, like that of Xiphostylus favosus (Pl. 13, fig. 4). Circular pores about as broad as the bars; eight to nine on the half equator. Surface smooth. Polar spines three-sided pyramidal, as broad at the base as a single hexagon; the longer spine as long as the major axis, the shorter half as long.