Subfamily Spongiommida, Haeckel
Definition.—Astrosphærida with spongy spherical or polyhedral shell (with or without enclosed concentric lattice-shells).
Genus 111. Spongiomma, 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. , 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. , 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, 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. , 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. , 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, 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, 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. , 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, 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, 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. , 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. , 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. , 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, 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. .
1. Lychnosphæra regina (Pl. , 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, 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. , 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, 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. , 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. , 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, 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, 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. , 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.