Dimensions.—Diameter of the outer sphere 0.12, pores 0.014, bars 0.007; inner sphere 0.06; length of the major spine 0.13, of the minor 0.05, greatest breadth 0.04.
Habitat.—Southern Pacific, surface, Station 289.
Definition.—Pores of the cortical shell irregular, of different size or form; surface smooth or a little rough.
6. Sphærostylus cottus, n. sp.
Cortical shell thick walled, smooth, about twice as broad as the medullary shell, with irregular, roundish pores, scarcely larger than the bars; fifteen to twenty on the half equator. Polar spines conical, the major once and a half to twice as long as the axis of the outer sphere, the minor scarcely as long as its radius.
Dimensions.—Diameter of the outer sphere 0.14, pores and bars 0.008 to 0.012; inner sphere 0.065; length of the major spine 0.2 to 0.3, of the minor 0.05 to 0.07, basal breadth 0.03.
Habitat.—Northern Atlantic, Færöe Channel, surface, John Murray.
7. Sphærostylus trigla, n. sp.
Cortical shell thin walled, smooth, three times as broad as the medullary shell, with irregular, roundish pores, two to three times as broad as the bars; ten to twelve on the half equator. Polar spines very unequal; the major three-sided pyramidal, one and a half times as long as the axis of the outer sphere; the minor scarcely as long as its radius, edged, pommel-like.
Dimensions.—Diameter of the outer sphere 0.12, pores 0.01 to 0.015, bars 0.005; inner sphere 0.04; length of the major spine 0.2, of the minor 0.05, breadth 0.03.
Habitat.—Northern Pacific, Station 241, depth 2300 fathoms.
Definition.—Pores of the cortical shell irregular, of different size or form; surface spiny or thorny.
8. Sphærostylus ophidium, n. sp. (Pl. 16, figs. 14, 15).
Stylosphæra ophidium, Haeckel, 1878, Atlas, loc. cit.
Cortical shell thin walled, thorny, twice as broad as the medullary shell, with irregular, roundish pores; eight to ten on the half equator. Polar spines conical, more or less curved or S-shaped; the minor scarcely as long as the axis of the outer sphere, the major two to three times as long.
Dimensions.—Diameter of the outer sphere 0.11, pores 0.01 to 0.017, bars 0.003 to 0.007; diameter of the inner sphere 0.06, pores 0.005 to 0.008, bars 0.002 to 0.004; length of the major polar spine 0.25, of the minor 0.1, basal breadth 0.03.
Habitat.—Indian Ocean, Madagascar, Rabbe, surface.
Definition.—Stylosphærida with two concentric lattice-spheres and two equal opposite spines, the distal ends of which are connected by a circular or elliptical ring.
The genus Saturnulus differs from the similar Saturnalis by the duplication of the spherical lattice-shell; the inner lies within, the outer without the central capsule.
1. Saturnulus circulus, n. sp.
Cortical shell smooth, twice as broad as the medullary shell, with regular, circular, hexagonally framed pores, of the same breadth as the bars; fourteen to sixteen on the half equator. Ring circular, smooth, without edges, its diameter three times as great as that of the sphere.
Dimensions.—Diameter of the outer sphere 0.08, pores and bars 0.004; of the inner sphere 0.04, of the ring 0.24.
Habitat.—Central Pacific, Station 272, surface.
2. Saturnulus annulus, n. sp.
Cortical shell smooth, three times as broad as the medullary shell, with regular, circular, hexagonally framed pores, of the same breadth as the bars; eighteen to twenty on the half equator. Ring elliptical, smooth, without edges, somewhat constricted at the poles of the minor axis, its major diameter four times as great as that of the sphere. Differs from Saturnalis annularis, Pl. 13, fig. 16, mainly in the possession of a medullary shell.
Dimensions.—Diameter of the outer sphere 0.1, pores and bars 0.005; inner sphere 0.033; major axis of the ring 0.4, minor 0.3.
Habitat.—North Pacific, Station 244, surface.
3. Saturnulus ellipticus, n. sp. (Pl. 16, fig. 16).
Cortical shell smooth, three times as broad as the medullary shell, with regular, circular pores, three times as broad as the bars; sixteen to eighteen on the half equator. Ring elliptical, smooth, without edges, its major diameter three times as great as that of the sphere.
Dimensions.—Diameter of the outer sphere 0.09, pores 0.006, bars 0.002; inner sphere 0.03; major axis of the elliptical ring 0.28, minor 0.24; thickness of the ring and the axial beams 0.008.
Habitat.—South Pacific, Station 300, surface.
4. Saturnulus planetes, n. sp. (Pl. 16, fig. 17).
Cortical shell smooth, twice as broad as the medullary shell, with regular, circular pores, of the same breadth as the bars; sixteen to eighteen on the half equator. Ring elliptical, smooth, with strong prominent edges, constricted at the poles of the minor axis, its major diameter three times as great as that of the outer sphere.
Dimensions.—Diameter of the outer sphere 0.08, pores and bars 0.005; inner sphere 0.035; major axis of the ring 0.25, minor axis 0.2; thickness of the ring and the axial beams 0.012.
Habitat.—Indian Ocean, Sunda Strait, Rabbe; Station 200, surface.
Definition.—Stylosphærida with three concentric spherical lattice-shells.
Definition.—Stylosphærida with three concentric lattice-spheres and two free spines of equal size and similar form.
The genus Amphisphæra differs from its probable ancestral form, Stylosphæra, in the triple spherical lattice-shell. Commonly two of these lie within the central capsule (medullary shell), whilst the third lies outside it (cortical shell). But sometimes this order is inverted, the cortical shell being double, the medullary shell simple; and perhaps these forms may better represent a peculiar genus, Amphisphæridium.
Definition.—Pores of the cortical shell regular, of nearly equal size and similar form; surface smooth or a little rough, without spines or thorns.
1. Amphisphæra neptunus, n. sp.
Radial proportion of the three concentric spheres = 4 : 2 : 1. Cortical shell thick walled, smooth, with regular, circular, hexagonally framed pores, of the same breadth as the bars; twelve to fifteen on the half equator. Polar spines three-sided pyramidal, with strong prominent edges, about as long as the radius of the outer shell, half as broad at the base. (Similar to Stylatractus neptunus, Pl. 17, fig. 6, but differs in the purely spherical form of the three concentric shells and the regular form of the network and of the polar spines.)
Dimensions.—Diameter of the outer shell 0.16, middle shell 0.08, inner shell 0.04; pores and bars of the cortical shell 0.008; length of the polar spines 0.08, basal breadth 0.04.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
2. Amphisphæra uranus, n. sp.
Radial proportion of the three spheres = 4 : 2 : 1. Cortical shell thick walled, smooth, with regular, circular pores, three times as broad as the bars; ten to twelve on the half equator. Polar spines three-sided pyramidal, about as long as the diameter of the outer shell, twice as broad at the base as one pore.
Dimensions.—Diameter of the outer shell 0.12, middle 0.06, inner 0.03; pores of the cortical shell 0.012, bars 0.004; length of the polar spines 0.1, basal breadth 0.024.
Habitat.—Western Indian Ocean, Zanzibar, 2200 fathoms, Pullen.
3. Amphisphæra jupiter, n. sp.
Radial proportion of the three spheres = 10 : 3 : 2. Cortical shell thick walled, smooth, with regular, circular pores, twice as broad as the bars; twenty to twenty-five on the half equator. Polar spines cylindro-conical, nearly as long as the axis of the outer shell, twice as broad at the base as one pore.
Dimensions.—Diameter of the outer shell 0.2, middle 0.06, inner 0.04; pores of the cortical shell 0.01, bars 0.005; length of the polar spines 0.15 to 0.18, breadth 0.02.
Habitat.—South Atlantic, Station 332, depth 2200 fathoms.
Definition.—Pores of the cortical shell regular, of nearly equal size and similar form; surface thorny or spiny.
4. Amphisphæra apollo, n. sp.
Radial proportion of the three spheres = 3 : 1.5 : 1. Cortical shell thick walled, spiny, with regular, circular, hexagonally framed pores, of the same breadth as the bars; twenty to twenty-two on the half equator. In each hexagon-corner (between three pores) a bristle-like radial spine. Polar spines cylindrical, with conical apex; one to one and a half times as long as the axis of the outer shell, as broad as three pores at the base. (Resembles closely Xiphosphæra pallas, Pl. 14, fig. 4, but differs in the presence of two medullary shells and the absence of the fine denticulations on the hexagonal crests.)
Dimensions.—Diameter of the outer shell 0.12, middle 0.06, inner 0.04; pores and bars of the cortical shell 0.006; length of the polar spines 0.15, breadth 0.02.
Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.
5. Amphisphæra mercurius, n. sp.
Radial proportion of the three spheres = 3 : 2 : 1. Cortical shell thin walled, spiny, with regular, circular pores, twice as broad as the bars; fifteen to eighteen on the half equator; between them short bristle-like radial spines. Polar spines three-sided pyramidal, about as long as the radius of the outer shell, one-third as broad at the base.
Dimensions.—Diameter of the outer shell 0.15, middle 0.09, inner 0.05; pores of the cortical shell 0.01, bars 0.005; length of the polar spines 0.09, basal breadth 0.03.
Habitat.—North Pacific, Station 244, depth 2900 fathoms.
Definition.—Pores of the cortical shell irregular, of different size or form; surface smooth or a little rough, without spines or thorns.
6. Amphisphæra cronos, n. sp. (Pl. 17, fig. 5).
Radial proportion of the three spheres = 3 : 2 : 1. Cortical shell thin walled, smooth, with irregular, roundish pores, two to four times as broad as the bars; eight to ten on the half equator. Outer medullary shell similar, but with pores of half the size, connected with the cortical shell by numerous radial beams; inner medullary shell with very small pores. Polar spines three-sided pyramidal, as long as the axis of the inner medullary shell, half as broad at the base.
Dimensions.—Diameter of the outer shell 0.12, middle 0.08, inner 0.04; pores of the cortical shell 0.01 to 0.02, bars 0.05; length of the polar spines 0.04, basal breadth 0.02.
Habitat.—South Atlantic, Station 330, surface.
7. Amphisphæra pluto, n. sp. (Pl. 17, figs. 7, 8).
Radial proportion of the three spheres about = 4 : 2 : 1 (or 11 : 7 : 3). Cortical shell thick walled, smooth, with very irregular, roundish pores, two to four times as broad as the bars; eight to ten on the half equator; often two to four pores confluent. Margin of their outer aperture double. Polar spines conical, double contoured, as long as the radius of the outer shell, one-third as broad at the base.
Dimensions.—Diameter of the outer shell 0.11, middle shell 0.07, inner shell 0.03; pores of the cortical shell 0.01 to 0.02, bars 0.06, length of the polar spines 0.06, basal breadth 0.02.
Habitat.—Central Pacific, Station 268, surface.
Definition.—Pores of the cortical shell irregular, of different size or form; surface spiny or thorny.
8. Amphisphæra mars, n. sp.
Radial proportion of the three spheres = 10 : 3 : 2. Cortical shell thin walled, thorny, with irregular, roundish pores, one to three times as broad as the bars; sixteen to twenty on the half equator. Irregularly scattered between them short conical thorns. Polar spines conical, about as long as the axis of the outer shell, as broad at the base as the inner shell.
Dimensions.—Diameter of the outer shell 0.2, middle shell 0.06, inner shell 0.04; pores of the cortical shell 0.005 to 0.02, bars 0.006; length of the polar spines 0.17, basal breadth 0.04.
Habitat.—North Atlantic, Gulf Stream, near Florida, depth 1500 fathoms, Schaffner.
Definition.—Stylosphærida with three concentric lattice-spheres and two free spines of different size or form.
The genus Amphistylus differs from its ancestral form, Amphisphæra, by the differentiation of both polar spines, and exhibits therefore the same relation to it that Sphærostylus bears to Stylosphæra.
1. Amphistylus clio, n. sp.
Radial proportion of the three spheres = 4 : 2 : 1. Cortical shell thick walled, smooth; its pores regular, circular, three times as broad as the bars; eighteen to twenty on the half equator. Polar spines three-sided pyramidal, very stout, as broad at the base as the inner medullary shell; major spine somewhat longer than the diameter of the cortical shell; minor spine scarcely half as long. (Similar to Stylosphæra clio, Pl. 16, fig. 7, but different in the double medullary shell and the different length of the polar spines.)
Dimensions.—Diameter of the outer sphere 0.15, middle 0.08, inner 0.04; pores of the outer shell 0.01, bars 0.003; length of the major spine 0.17, minor 0.07, basal breadth 0.04.
Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.
2. Amphistylus hippocampus, n. sp.
Radial proportion of the three spheres = 3 : 2 : 1. Cortical shell thick walled, smooth; its pores regular, circular, hexagonally lobed, three times as broad as the bars; twelve to fifteen on the half equator. Major polar spine three-sided pyramidal, about as long as the axis of cortical shell; minor spine pommel-like, edged, scarcely one-third as long. (Similar to Sphærostylus hippocampus, Pl. 16, figs. 10, 11, but differs in the larger size, the double medullary shell, and the straight, not curved, major spine.)
Dimensions.—Diameter of the outer sphere 0.11, middle 0.07, inner 0.035; pores of the outer shell 0.011, bars 0.004; length of the major spine 0.12, of the minor 0.04, breadth 0.03.
Habitat.—North Pacific, Station 244, depth 2900 fathoms.
3. Amphistylus glyptodon, n. sp.
Radial proportion of the three spheres = 6 : 3 : 1. Cortical shell thick walled, spiny, with irregular, roundish pores, two to four times as broad as the bars; ten to twelve on the half equator. Inner aperture of each pore closed by a thin fenestrated lamella with five to seven small pores. Major polar spine three-sided pyramidal, longer than the diameter of the outer sphere; minor polar spine scarcely as long as its radius, pommel-shaped. (Similar to Xiphatractus glyptodon, Pl. 17, figs. 9, 10, but differs in the spherical, not ellipsoidal, form of the three shells and the size of the polar spines.)
Dimensions.—Diameter of the outer sphere 0.12, middle 0.06, inner 0.02; pores and spines of the outer shell 0.01 to 0.02, bars and porules 0.006; length of the major polar spine 0.15, of the minor 0.05, breadth 0.04.
Habitat.—South Pacific, Station 285, depth 2375 fathoms.
Definition.—Stylosphærida with three concentric lattice-spheres and two equal opposite spines, connected at the distal end by a circular or elliptical ring.
The genus Saturninus differs from the similar Saturnulus by the triplication of the spherical lattice-shell; the inner shell is enclosed in the central capsule, whilst both the others lie outside it.
1. Saturninus triplex, n. sp.
Radial proportion of the three spheres = 4 : 3 : 1. Inner cortical shell with regular, circular pores, of the same breadth as the bars, sixteen to eighteen on the half equator; outer cortical shell connected with the inner by numerous bristle-like radial spines, network very delicate, cobweb-shaped, with irregular polygonal meshes. Ring elliptical, two and a half times as broad as the outer shell.
Dimensions.—Diameter of the inner sphere 0.03, middle 0.09, outer 0.12; pores and bars of the middle shell 0.004; major axis of the elliptical ring 0.3, minor 0.25; thickness of the ring and the axial beams 0.008.
Habitat.—Central Pacific, Station 272, surface.
Definition.—Stylosphærida with four concentric spherical lattice-shells (two medullary and two cortical).
Definition.—Stylosphærida with four concentric lattice-spheres and two free spines of equal size and similar form.
The genus Stylocromyum differs from its probable ancestral form, Amphisphæra, by the duplication of the cortical shell; two opposite radial beams, piercing the wall of the central capsule, connect it with the double medullary shell, and are prolonged outside into two equal spines.
1. Stylocromyum amphiconus, n. sp.
Surface of the shell smooth. Radial proportion of the four spheres = 1 : 2 : 8 : 9. Two medullary shells inside the central capsule, two cortical shells outside it. Interval between the second and third shells the greatest. Pores of all the shells regular, circular, two to four times as broad as the bars. Both polar spines equal, conical, about as long as the axis of the outermost sphere, as broad at the base as the innermost.
Dimensions.—Diameter of the four spheres—(A) inner medullary shell 0.03, (B) outer medullary shell 0.06, (C) inner cortical shell 0.25, (D) outer cortical shell 0.28; length of the polar spines 0.3, basal breadth 0.03.
Habitat.—Central Pacific, Station 273, depth 2350 fathoms.
2. Stylocromyum amphipyramis, n. sp.
Surface of the shell smooth. Radial proportion of the four spheres = 2 : 3 : 6 : 8. Both medullary shells with regular, circular pores, twice as broad as the bars. Both cortical shells with irregular, roundish, much larger pores, three to six times as broad as the bars. Both polar spines equal or nearly equal, three-sided pyramidal, about as long as the axis of the third shell.
Dimensions.—Diameter of the four spheres—(A) 0.04, (B) 0.06, (C) 0.12, (D) 0.16; length of the polar spines 0.11, basal breadth 0.02.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
Definition.—Stylosphærida with four concentric lattice-spheres and two free spines of different size or form.
The genus Cromyostylus differs from its ancestral form, Stylocromyum, in the differentiation of the two unequal polar spines.
1. Cromyostylus gladius, n. sp.
Surface of the shell smooth. Radial proportion of the four spheres = 1 : 3 : 10 : 12. Both medullary shells with regular, circular, simple pores. Inner cortical shell with regular, circular, hexagonally framed pores, twice as broad as the bars. From each hexagon-corner arises a bristle-shaped radial spine, which at the distal end gives off three thread-like branches; by communication of these threads (at equal distances from the centre) the delicate outer medullary shell is formed. The polar spines very different; major spine six-sided pyramidal, longer than the diameter of the shell; minor pommel-shaped, shorter than the radius (similar to Xiphatractus glyptodon, Pl. 17, figs. 9, 10, but different in the double spherical cortical shell).
Dimensions.—Diameter of the four spheres—(A) 0.02, (B) 0.06, (C) 0.2, (D) 0.24; length of the major spine 0.3, of the minor 0.1.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
Definition.—Stylosphærida with five or more concentric, spherical lattice-shells.
Definition.—Stylosphærida with five to six or more concentric lattice-shells and two free opposite spines of equal size and similar form.
The genus Caryostylus differs from its ancestral form, Stylocromyum, by the multiplication of the concentric spheres, the number of which amounts to five or six or more. I have only observed one single species of this genus. Some similar forms which in my Prodromus (1881, p. 454) were annexed to it, and disposed in three nearly allied genera (Caryoxiphus, Caryodoras, Caryolonche), have now been proved to belong to other groups, mainly ellipsoidal Druppulida.
1. Caryostylus hexalepas, n. sp.
Surface of the spherical shell smooth. Radial proportion of the component six concentric shells = 1 : 2 : 7 : 9 : 12 : 15. Both medullary shells connected only by six radial beams, opposite in pairs in the three dimensive axes. Between second and third shell numerous (twenty regularly disposed?) radial beams. Four cortical shells connected by very numerous (sixty to eighty or more?) short radial beams. Pores of all six shells regular, circular, the size increasing towards the surface, two to three times as broad as the bars. Two opposite polar spines very large, of equal size, three times as long as the shell radius, cylindrical, club-shaped at the thicker distal end. (The whole shell structure is similar to Pl. 15, fig. 2, but the shells are spherical, not ellipsoidal.)
Dimensions.—Diameter of the six spheres—(A) 0.02, (B) 0.04, (C) 0.15, (D) 0.18, (E) 0.24, (F) 0.3; length of the spines 0.5.
Habitat.—West Tropical Pacific, Station 225, depth 4475 fathoms.
Definition.—Stylosphærida with spherical spongy shell (with or without enclosed latticed medullary shells).
Definition.—Stylosphærida with a solid sphere of spongy framework, and with two opposite free radial spines.
The genus Spongolonchis differs from its probable ancestral form, Styptosphæra, by the development of two opposite radial spines situated in one axis.
1. Spongolonchis compacta, n. sp.
Spongy framework of the spherical shell very compact, with small meshes, three to four times as broad as the bars. Surface rough, but not spiny. Two polar spines pyramidal, only as long as the radius of the shell, one-third as broad at the base.
Dimensions.—Diameter of the shell 0.2; length of the spines 0.1, basal breadth 0.03.
Habitat.—Central Pacific, Station 274, depth 2750 fathoms.
2. Spongolonchis laxa, n. sp.
Spongy framework loose, with large meshes, ten to twelve times as broad as the bars. Surface spiny. Two polar spines three-sided prismatic, longer than the diameter of the shell (broken off in the observed specimen).
Dimensions.—Diameter of the shell 0.5; length of the spine 0.6 and more, breadth 0.02.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
Definition.—Stylosphærida with spongy spherical cortical shell, enclosing in the centre a simple latticed medullary shell, and with two opposite free radial spines.
The genus Spongostylus may probably be derived from Spongoplegma by development of two opposite radial spines in one axis.
1. Spongostylus hastatus, n. sp.
Spongy cortical shell with compact framework, twice as broad as the enclosed medullary shell, the pores of which are regular, circular, twice as broad as the bars. Two polar spines, three times as long as the radius of the shell, in the basal two-thirds cylindrical, in the distal third compressed, two-edged, spear-shaped.
Dimensions.—Diameter of the cortical shell 0.1, medullary shell 0.05; length of the spines 0.15.
Habitat.—South Atlantic, Station 335, depth 1425 fathoms.
2. Spongostylus gladiatus, Haeckel.
Stylosphæra holosphæra, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 299, Taf. viii. fig. 14.
Spongy cortical shell with rather compact framework, four times as broad as the enclosed medullary shell, the pores of which are irregular, roundish, three to four times as broad as the bars. Two polar spines sword-shaped, two-edged, as long as the shell diameter.
Dimensions.—Diameter of the cortical shell 0.24, medullary shell 0.06; length of the spines 0.25.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms; Philippine Sea, depth 3300 fathoms.
3. Spongostylus serratus, n. sp.
Spongy cortical shell with lax framework, ten to twelve times as broad as the enclosed medullary shell, the pores of which are irregular, roundish, once and a half to twice as broad as the bars. Two polar spines longer than the shell diameter (broken off in the observed specimen), three-sided prismatical, with three straight serrated edges.
Dimensions.—Diameter of the cortical shell 0.5, medullary shell 0.04; length of the spines 0.6 or more.
Habitat.—South Pacific, Station 285, depth 2375 fathoms.
Definition.—Stylosphærida with spongy spherical cortical shell, enclosing two concentric spherical latticed medullary shells, and with two opposite, free radial spines.
The genus Spongostylidium differs from Spongostylus by duplication of the latticed medullary shell, and therefore bears the same relation to it as Spongodictyon to Spongoplegma.
1. Spongostylidium streptacanthum, n. sp.
Both medullary shells spherical, with small, regular, circular pores, twice as broad as the bars (outer twice as broad as the inner). Spongy cortical shell enclosing it with dense framework, four times as broad as the outer medullary shell. Two polar spines very large, four times as long as the diameter of the outer shell; as broad as the inner medullary shell, with three dentated, spirally contorted edges. (Very similar to the common Spongosphæra streptacantha and to Hexadoridium streptacanthum, but with only two opposite spines in one axis.)
Dimensions.—Diameter of the cortical shell 0.16, of the outer medullary shell 0.04, inner 0.02; length of the spines 0.7 and more, breadth 0.02.
Habitat.—Indian Ocean, Cocos Islands, Rabbe.
Staurosphærida, Haeckel, 1881, Prodromus, p. 449.
Definition.—Sphæroidea with four radial spines on the surface of the spherical shell, forming a regular cross, being opposite in pairs in two axes perpendicular to one another; living solitary (not associated in colonies).
The family Staurosphærida is distinguished from the other Sphæroidea by the possession of four radial spines, which are opposite in pairs in two perpendicularly crossed axes. By these "two main axes" an equatorial plane is determined, which approximates them to the Discoidea. But in the latter the shells as well as the central capsule become more or less flattened, lenticular, or discoidal, whilst in the former they remain spherical. However, some forms of both groups are very similar, and inspection from different sides (and mainly from the margin of the equatorial plane) is required to determine the spherical (not compressed) shell-form of the Staurosphærida. As a rule the species of this family are much rarer, and much less numerous, than those of all the other Sphæroidea.
The most simple Staurosphærida are the Staurostylida, with one single spherical lattice-shell. To this ancestral group all other subfamilies can be opposed as "Staurosphærida concentrica," since their carapace is composed of two or more concentric lattice-shells; two in the Staurolonchida, three in the Stauracontida, four in the Staurocromyida, five or more in the Staurocaryida. In all these four subfamilies the concentric shells are simple (not spongy) fenestrated spheres. In a sixth subfamily, in the Staurodorida, the shell is wholly or partially composed of irregular spongy wickerwork, with or without a medullary shell in the centre.
The Four Radial Spines in all Staurosphærida are normally opposed in pairs in two axes perpendicular one to another, and therefore together form a rectangular cross. But in many species besides this normal form individual abnormalities occur, in which the four spines in the equatorial plane are not quite accurately opposed, so that the four angles between them are not right angles, but more or less unequal. More rarely also their position in the equatorial plane is not accurately retained, so that they are placed in two, three, or four different meridian planes, intersecting at very small variable angles.
In the greater part of Staurosphærida all four radial spines are quite equal, and of the same size and form. But in some genera there takes place a more or less considerable differentiation of the four spines, commonly in pairs, so that the two opposite spines of each pair are equal, but the pairs different (Staurostylus, Staurolonchidium). More rarely also both spines of one pair become unequal, whilst those of the other pair remain equal (Stauroxiphos). Very rarely all four spines assume a different size or form.
|
I. Subfamily Staurostylida. (Shell one single lattice-sphere.) |
brace | All four spines equal, | 60. Staurosphæra. | ||
| Four spines different in pairs, | 61. Staurostylus. | ||||
| One spine larger than the three others, | 62. Stylostaurus. | ||||
|
II. Subfamily Staurolonchida. (Shell with two concentric lattice-spheres.) |
brace | All four spines equal, | brace | Simple, | 63. Staurolonche. |
| Branched, | 64. Staurancistra. | ||||
| Four spines different in pairs, | 65. Staurolonchidium. | ||||
| One spine larger than the three others, | 66. Stauroxiphos. | ||||
|
III. Subfamily Stauracontida. (Shell with three concentric spheres.) |
brace | All four spines equal, simple, | 67. Stauracontium. | ||
|
IV. Subfamily Staurocromyida. (Shell with four concentric spheres.) |
brace | All four spines equal, | brace | Simple, | 68. Staurocromyum. |
| Branched, | 69. Cromyostaurus. | ||||
|
V. Subfamily Staurocaryida. (Shell with five or more concentric spheres.) |
brace | All four spines equal, | 70. Staurocaryum. | ||
|
VI. Subfamily Staurodorida. (Shell a spongy sphere.) |
brace | Solid spongy sphere without medullary shell, | 71. Staurodoras. | ||
| I. Subfamily Staurostylida. (Shell one single lattice-sphere.) | ||||||
| All four spines equal, | ||||||
| 60. Staurosphæra. | ||||||
| Four spines different in pairs, | ||||||
| 61. Staurostylus. | ||||||
| One spine larger than the three others, | ||||||
| 62. Stylostaurus. | ||||||
| II. Subfamily Staurolonchida. (Shell with two concentric lattice-spheres.) | ||||||
| All four spines equal, | ||||||
| Simple, | ||||||
| 63. Staurolonche. | ||||||
| Branched, | ||||||
| 64. Staurancistra. | ||||||
| Four spines different in pairs, | ||||||
| 65. Staurolonchidium. | ||||||
| One spine larger than the three others, | ||||||
| 66. Stauroxiphos. | ||||||
| III. Subfamily Stauracontida. (Shell with three concentric spheres.) | ||||||
| All four spines equal, simple, | ||||||
| 67. Stauracontium. | ||||||
| IV. Subfamily Staurocromyida. (Shell with four concentric spheres.) | ||||||
| All four spines equal, | ||||||
| Simple, | ||||||
| 68. Staurocromyum. | ||||||
| Branched, | ||||||
| 69. Cromyostaurus. | ||||||
| V. Subfamily Staurocaryida. (Shell with five or more concentric spheres.) | ||||||
| All four spines equal, | ||||||
| 70. Staurocaryum. | ||||||
| VI. Subfamily Staurodorida. (Shell a spongy sphere.) | ||||||
| Solid spongy sphere without medullary shell, | ||||||
| 71. Staurodoras. | ||||||
Definition.—Staurosphærida with one single spherical lattice-shell.
Definition.—Staurosphærida with a single lattice-sphere and four crossed equal spines.
The genus Staurosphæra may be regarded as the common ancestral form of this subfamily, since it represents their most simple and primitive form. From the surface of the simple lattice-sphere, enclosing the central capsule, arise four equal, simple, radial spines, opposite in pairs in two diameters, perpendicular one to another. Staurosphæra may be derived phylogenetically either from Cenosphæra by production of the four spines, or from Hexastylus by reduction of two opposite spines.