Definition.—Radial main spines with three rows of lateral branches (one row on each edge).
3. Astrosphæra sideræa, n. sp.
Inner shell with regular, hexagonal meshes, six times as broad as the bars, and covered with numerous short bristle-shaped by-spines; outer shell four times as broad, with simple triangular meshes, and rows of long bristle-shaped by-spines arising from the bars. Radial main spines with three serrated edges and three rows of lateral branches (four branches on each edge).
Dimensions.—Diameter of the outer shell 0.6, inner 0.15.
Habitat.—Central Pacific, Station 266, surface.
4. Astrosphæra stellata, n. sp. (Pl. 19, fig. 5).
Diplosphæra stellata, Haeckel, 1881, Prodrom. et Atlas.
Inner shell with regular, hexagonal, six-rayed meshes, each bar being crossed by a transverse tangential rod, at each nodal-point a long bristle-shaped by-spine; outer shell three times as broad, with simple triangular meshes and denticulated thin bars, bearing a row of bristle-shaped radial by-spines. Radial main spines in the proximal half with three serrated edges, in the distal half with three rows of curved lateral branches (five branches on each edge).
Dimensions.—Diameter of the outer shell 0.6, inner 0.2.
Habitat.—Central Pacific, Station 274, surface.
Definition.—Astrosphærida with three concentric, spherical, lattice-shells, united by radial beams.
Definition.—Astrosphærida with three concentric lattice-spheres and numerous simple radial spines of one kind.
The genus Actinomma is here restricted to those Sphæroidea which combine the possession of three concentric lattice-shells with numerous radial spines on the surface; the spines are all simple, being of one and the same kind. Commonly two of the three shells are intracapsular medullary shells, connected by radial beams (piercing the central capsule) with the outer, extracapsular, cortical shell. But in some species only one medullary shell is enclosed in the central capsule, whilst both other shells lie outside it. In such case the distance between these two cortical shells is much smaller than their distance from the simple internal medullary shell. These forms correspond more to aculeate Rhodosphæræ, whilst the others resemble aculeate Thecosphæræ.
Definition.—Pores of the cortical shell regular, of nearly equal size and similar form; spines on the entire surface (commonly one spine at each nodal-point).
1. Actinomma hexagonium, n. sp.
Cortical shell, as well as both medullary shells, very thin walled, with regular, hexagonal pores and thread-like bars between them. Pores of the outer shell twice as broad as those of the middle, and three times as broad as those of the inner shells. Radial proportion of the three spheres = 1 : 3 : 9; about twenty thin radial beams between them. At each nodal-point of the surface arises one bristle-shaped radial spine, half as long as the radius.
Dimensions.—Diameter of the outer shell 0.22, middle 0.07, inner 0.025; meshes of the cortical shell 0.01; length of the spines 0.05.
Habitat.—Central Pacific, Stations 270 to 274, surface.
2. Actinomma facetum, n. sp.
Cortical shell thick walled, with regular, circular, hexagonally framed pores, three times as broad as the bars. Pores of both medullary shells regular, circular. Radial proportion of the three spheres = 1 : 2 : 4; about forty thin radial beams between them. At each nodal-point of the surface arises one short, three-sided pyramidal, radial spine, about one-third as long as the radius.
Dimensions.—Diameter of the outer shell 0.16, middle 0.08, inner 0.04; cortical pores 0.012, bars 0.004; length of the spines 0.03, basal breadth 0.015.
Habitat.—North Pacific, Station 253, depth 3125 fathoms.
3. Actinomma anthomma, n. sp.
Cortical shell thick walled, with regular, six-lobed pores, twice as broad as the bars. At each nodal-point of the surface is one short conical radial spine, as long as the diameter of the pores; one corresponding to each lobe, and there is therefore around each pore a regular corona of six spines, as in Haliomma lirianthus (Pl. 28, fig. 1b). Both medullary shells with simple, circular, regular pores. Radial proportion of the three spheres = 1 : 2.5 : 7; radial beams between them only six, opposite in pairs in the three dimensive axes.
Dimensions.—Diameter of the outer shell 0.2, middle 0.075, inner 0.003; cortical pores 0.01, bars 0.005; length of the spines 0.01.
Habitat.—Central Pacific, Station 271, surface.
4. Actinomma castanomma, n. sp.
Cortical shell as well as both medullary shells thick walled, with regular, circular pores, twice as broad as the bars; between them at each nodal-point one bristle-shaped radial spine, one-third as long as the radius, with conical base. Radial proportion of the three spheres = 2 : 3 : 8; only six radial beams between them (opposed in pairs in the three dimensive axes).
Dimensions.—Diameter of the outer shell 0.15, middle 0.06, inner 0.04; cortical pores 0.008, bars 0.004; length of the spines 0.025.
Habitat.—South Atlantic, Station 333, surface.
5. Actinomma entactinia, Stöhr.
Actinomma entactinia, Stöhr, 1880, Palæontogr., vol. xxvi. p. 93, Taf. ii. fig. 12.
Cortical shell as well as both medullary shells thick walled, with regular, circular pores, of the same breadth as the bars. Radial proportion of the three spheres = 1 : 3 : 8; radial beams between them very numerous (thirty to fifty or more?). Entire surface covered with short thick conical spines, only one-fifth as long as the radius.
Dimensions.—Diameter of the outer shell 0.16, middle 0.06, inner 0.02; cortical pores and bars 0.007; length of the spines 0.015.
Habitat.—Fossil in the Tertiary rocks of Sicily, Grotte, Caltanisetta.
Definition.—Pores of the outer shell regular, of nearly equal size and similar form; spines not over the entire surface, but scattered at intervals (their number smaller than that of the nodal-points).
6. Actinomma japonicum, n. sp.
Cortical shell thick walled, with regular, circular, hexagonally framed pores, three times as broad as the bars. Both medullary shells with simple, circular, regular pores, of the same breadth as the bars. Radial proportion of the three spheres = 2 : 5 : 9; radial beams between them twenty, prolonged outside into twenty symmetrically disposed, three-sided pyramidal spines, as long as the radius.
Dimensions.—Diameter of the outer shell 0.18, middle 0.1, inner 0.04; cortical pores 0.01, bars 0.003; length of the spines 0.1, basal breadth 0.012.
Habitat.—North Pacific, Station 240, east of Japan, surface.
7. Actinomma denticulatum, n. sp. (Pl. 29, fig. 3).
Cortical shell thick walled, with regular, circular, double-edged pores, twice as broad as the bars. Forty to fifty radial spines, three-sided pyramidal, half as long as the radius, with three elegantly denticulated edges. Radial proportion of the three spheres = 1 : 2 : 5. (Differs from Haliomma denticulatum only in the double medullary shell and larger size.)
Dimensions.—Diameter of the outer shell 0.14, middle 0.06, inner 0.03; cortical pores 0.01, bars 0.005; length of the spines 0.04, basal breadth 0.01.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
8. Actinomma trinacrium, Haeckel.
Actinomma trinacrium, Haeckel, 1862, Monogr. d. Radiol., p. 441, Taf. xxiv. figs. 6-8.
Haliomma trinacrium, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 815.
Cortical shell as well as both medullary shells thin walled, with subregular, circular pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 3 : 9; radial beams between them twenty, prolonged outside into strong, three-sided pyramidal spines, as long as the radius; between them, on the surface, numerous similar spines. Sometimes the latter remain smaller, the pores more irregular, and then this species corresponds to Echinomma trinacrium.
Dimensions.—Diameter of the outer shell 0.09, middle 0.03, inner 0.01; cortical pores 0.008, bars 0.004; length of the spines 0.04, basal breadth 0.01.
Habitat.—Mediterranean (Messina, Corfu, Haeckel), surface.
9. Actinomma pachyderma, n. sp. (Pl. 29, figs. 4, 5).
Cortical shell very thick walled, with regular, circular, double-edged pores, twice as broad as the bars. Both medullary shells with simple, small, circular pores, of the same breadth as the bars. Radial proportion of the three spheres = 1 : 2 : 4; radial spines about twenty, conical, shorter than the radius, prolonged inside into twenty very thin connecting beams (fig. 4).
Dimensions.—Diameter of the outer shell 0.08, middle 0.04, inner 0.02; cortical pores 0.01; bars 0.005; length of the spines 0.03, basal breadth 0.01.
Habitat.—South Pacific, Station 297, depth 1775 fathoms.
Definition.—Pores of the cortical shell irregular, of different size and form; spines over the entire surface (commonly one spine at each nodal-point).
10. Actinomma spinigerum, Stöhr.
Actinomma spinigerum, Stöhr, 1880, Palæontogr., vol. xxvi. p. 92, Taf. ii. fig. 10.
Cortical shell thick walled, with irregular, roundish, or subcircular pores, twice to four times as broad as the bars. Radial proportion of the three spheres = 1 : 3 : 8; between them eight (?) connecting radial beams. Entire surface densely covered with small conical spines, not larger than the pores.
Dimensions.—Diameter of the outer shell 0.17, middle 0.07, inner 0.023; cortical pores 0.006 to 0.012, bars 0.003; length of the spines 0.01.
Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
11. Actinomma hirsutum, n. sp.
Cortical shell thick walled, with irregular, roundish pores, about the same breadth as the bars. Radial proportion of the three spheres = 1 : 2 : 8; between them numerous (twenty to thirty or more) cylindrical connecting beams. Entire surface densely covered with innumerable small bristle-shaped spines, as long as the diameter of the inner shell.
Dimensions.—Diameter of the outer shell 0.25, middle 0.06, inner 0.03; cortical pores and bars 0.004 to 0.008; length of the spines 0.03.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
Definition.—Pores of the cortical shell irregular, of different size and form; spines not over the entire surface, but scattered at intervals (their number smaller than that of the nodal-points).
12. Actinomma capillaceum, n. sp. (Pl. 29, fig. 6).
Cortical shell very thin walled, with irregular, polygonal meshes (sixteen to eighteen on the radius), three to six times as broad as the bars. Both medullary shells with smaller pores of the same structure. Radial proportion of the three spheres = 1 : 2.5 : 7; radial connecting beams between them very thin and numerous (one hundred and twenty to one hundred and fifty or more), each prolonged outside into a short three-sided pyramidal spine, as long as the radius of the inner shell. (Similar to Haliomma capillaceum.)
Dimensions.—Diameter of the outer shell 0.27, middle 0.1, inner 0.04; cortical pores 0.01 to 0.02, bars 0.003; length of the spines 0.02, basal breadth 0.005.
Habitat.—Central Pacific, Stations 266 to 274, surface.
13. Actinomma arcadophorum, n. sp. (Pl. 29, figs. 7, 8).
Cortical shell very thin walled, with irregular, polygonal meshes, ten to twenty times as broad as the bars; twelve to sixteen on the radius. Both medullary shells with similar delicate network. Radial proportion of the three spheres = 1 : 2 : 6; numerous thin radial beams (forty to eighty or more) connect both medullary shells and alternate with other beams, which arise from arcade-shaped protuberances of the outer medullary shell, and connect it with the cortical shell. Outer prolongations of these form the bristle-shaped spines of the surface.
Dimensions.—Diameter of the outer shell 0.22, middle 0.09, inner 0.04; cortical pores 0.01 to 0.02, bars 0.001 to 0.002; length of the radial spines 0.2.
Habitat.—Central Pacific, Station 266, surface.
14. Actinomma schwageri, Stöhr.
Actinomma schwageri, Stöhr, 1880, Palæontogr., vol. xxvi. p. 92, Taf. ii. fig. 9a, b.
Cortical shell thick walled, with irregular, large, polygonal meshes, five to twelve times as broad as the bars; six to eight on the radius. Both medullary shells with very small, circular, regular pores. Radial proportion of the three spheres = 1 : 2 : 9; connecting radial beams between them nine, prolonged outside into nine short stout, three-sided pyramidal spines, as long as the diameter of the inner shell.
Dimensions.—Diameter of the outer shell 0.17, middle 0.04, inner 0.02; cortical pores 0.01 to 0.03, bars 0.006 and less; length of the spines 0.02, basal breadth 0.01.
Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
15. Actinomma dodecomma, n. sp.
Cortical shell thin walled, with irregular, roundish pores, three to six times as broad as the bars. Both medullary shells with regular, circular pores, twice as broad as the bars. Radial proportion of the three shells = 1 : 2.5 : 7; connecting radial beams between them twelve, regularly disposed, prolonged outside into twelve strong, three-sided pyramidal spines, as long as the radius.
Dimensions.—Diameter of the outer shell 0.14, middle 0.05, inner 0.02; cortical pores 0.008 to 0.018, bars 0.003; length of the spines 0.08, breadth 0.02.
Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.
16. Actinomma pachycapsa, n. sp.
Cortical shell very thick walled, with irregular, roundish pores, twice to four times as broad as the bars; twelve to sixteen on the radius. Radial proportion of the three spheres = 1 : 3 : 12. Both medullary shells of similar irregular structure, connected with the cortical shell by twelve regularly disposed radial beams, which are prolonged outside into twelve short stout conical spines, as long as the diameter of the middle shell.
Dimensions.—Diameter of the outer shell 0.25, middle 0.06, inner 0.02; cortical pores 0.006 to 0.012, bars 0.003; length of the spines 0.05, breadth 0.02.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
17. Actinomma giganteum, n. sp.
Cortical shell thick walled, little larger than the outer medullary shell, whilst the inner is only one-tenth as large. Pores of all three shells irregular, roundish, or subcircular, twice to three times as broad as the bars, on an average twice as large in the outer and middle as in the inner shell. Sixty to eighty short conical radial spines on the surface, about as long as the diameter of the inner shell, and one-fourth as broad at the base. Radial proportion of the three spheres = 1 : 9 : 10.
Dimensions.—Diameter of the outer shell 0.4 to 0.5, middle 0.35 to 0.45, inner 0.05 to 0.06.
Habitat.—Fossil in Barbados.
Definition.—Astrosphærida with three concentric lattice-spheres and numerous simple radial spines of two different kinds; larger main spines and smaller by-spines.
The genus Echinomma, differs from its ancestral form, Actinomma, in the differentiation of the radial spines. Whilst a large number of small by-spines cover the entire surface, a smaller number of large main spines are scattered over it, or limited to certain regularly distributed points. It represents Heliosoma among the Haliommida.
Definition.—Pores of the cortical shell regular, of nearly equal size and similar form.
1. Echinomma echinidium, n. sp.
Cortical shell thin walled, with regular, hexagonal pores, four times as broad as the bars; ten to twelve on the radius. Both medullary shells with regular, circular pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 5. Surface covered with short bristle-shaped by-spines (one in every hexagon-corner); twenty main spines regularly disposed, three-sided pyramidal, as long as the diameter of the inner shell.
Dimensions.—Diameter of the outer shell 0.1, middle 0.045, inner 0.02; cortical pores 0.008, bars 0.002; length of the main spines 0.02, breadth 0.01.
Habitat.—South Pacific, Station 295, surface.
2. Echinomma cidaris, n. sp.
Cortical shell thin walled, with regular, circular, hexagonally framed pores, twice as broad as the bars; six to eight on the radius. Both medullary shells with simple, circular pores. Radial proportion of the three spheres = 1 : 2 : 6. Surface covered with short bristle-shaped by-spines, half as long as the forty to fifty main spines, which are three-sided pyramidal, and reach the radius of the shell.
Dimensions.—Diameter of the outer shell 0.18, middle 0.06, inner 0.03; cortical pores 0.01, bars 0.005; length of the main spines 0.08, basal breadth 0.015.
Habitat.—Central Pacific, Station 272, surface.
3. Echinomma aculeatum, Haeckel.
Actinomma aculeatum, Stöhr, 1880 Palæontogr., vol. xxvi. p. 92, Taf. ii. fig. 11.
Cortical shell thick walled with regular circular pores, of the same breadth as the bars; eight to ten on the radius. Radial proportion of the three spheres = 1 : 2 : 8. Surface covered with short conical by-spines about twenty strong main spines, three-sided pyramidal, one-third as long as the shell diameter.
Dimensions.—Diameter of the outer shell 0.16, middle 0.04, inner 0.02; cortical pores and bars 0.003; length of the main spines 0.05, basal breadth 0.013.
Habitat.—Fossil in the Tertiary rocks of Sicily and Barbados; living in the Atlantic, Station 332, depth 2200 fathoms.
4. Echinomma diadema, n. sp.
Cortical shell thick walled with regular circular pores, twice as broad as the bars; sixteen to eighteen on the radius. Radial proportion of the three spheres = 1 : 3 : 11. Surface covered with short bristle-shaped by-spines one third as long as the twelve stout conical main spines, which reach in length the radius, and lie opposite in pairs in six axes.
Dimensions.—Diameter of the outer shell 0.22, middle 0.06, inner 0.02; cortical pores 0.006, bars 0.003 length of the main spines 0.12, basal breadth 0.02.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
Definition.—Pores of the cortical shell irregular, of different size or form.
5. Echinomma sphærechinus, n. sp. (Pl. 29, fig. 2).
Actinomma sphærechinus, Haeckel, 1879, Atlas (pl. xxix. fig. 2).
Cortical shell thin walled, with irregular, roundish pores, twice to five times as broad as the bars; five to seven on the radius. Both medullary shells with regular, circular pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 4. Surface covered with thirty to fifty pyramidal main spines, as long as the diameter of the inner shell, and with numerous small conical by-spines of half the length.
Dimensions.—Diameter of the outer shell 0.11, middle 0.05, inner 0.025; cortical pores 0.01 to 0.02, bars 0.004; length of the main spines 0.03, basal breadth 0.005.
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.
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.
Definition.—Astrosphærida with four concentric spherical lattice-shells.
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.
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.
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.
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.
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.