Definition.—Margin of the disk with a solid equatorial girdle, or a corona of spines.
2. Phacostaurus quadrigatus, n. sp.
Disk with smooth surface, four times as broad as the outer and ten times as broad as the inner medullary shell. Pores irregular, roundish; fifteen to sixteen on the diameter of the disk. Margin with a broad solid equatorial girdle, from which arise four crossed spines, conical, as long as the radius of the disk.
Dimensions.—Diameter of the disk 0.2, of the outer medullary shell 0.05, of the inner 0.02; length of the spines 0.1, basal breadth 0.03.
Habitat.—South Pacific, Station 300, depth 1375 fathoms.
3. Phacostaurus magnificus, n. sp. (Pl. 31, figs. 7, 8).
Astrostaurus magnificus, Haeckel, 1881, Prodromus et Atlas (pl. xxxi. figs.7, 8).
Disk with smooth surface, three times as broad as the outer and nine times as broad as the inner medullary shell. Pores regular, circular; thirteen to fourteen on the diameter of the disk. Margin with a corona of fifty to sixty conical spines of unequal length. Four spines of the cross very large pyramidal, deeply sulcated, longer than the radius of the disk, and as broad at the base as the radius of the medullary shell.
Dimensions.—Diameter of the disk 0.22, of the outer medullary shell 0.07, of the inner 0.025; length of the four spines 0.16, basal breadth 0.04.
Habitat.—Indian Ocean, Madagascar, Rabbe, surface.
Definition.—Phacodiscida with simple medullary shell and with six radial spines on the margin of the disk placed in the equatorial plane.
The genus Distriactis exhibits on the margin of the lenticular phacoid shell six radial solid spines. Their distance is commonly equal, rarely unequal. Either all six spines are of equal size and similar form, or three larger (perradial) alternating with three smaller (interradial), so that Distriactis appears to be derived from Triactiscus by development of three secondary between three primary spines.
1. Distriactis liriantha, n. sp.
Disk smooth, four times as broad as the medullary shell, with regular, circular pores (about ten on the radius). Six marginal spines of equal size and at equal distances, triangular, sulcate, half as long as the radius. (Similar to Heliosestrum medusinum, Pl. 34, fig. 6.)
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the spines 0.05, basal breadth 0.04.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
2. Distriactis corallantha, n. sp.
Disk thorny, three times as broad as the medullary shell, with regular, circular pores, about eight on the radius. Six marginal spines of equal size and equidistant, conical, nearly as long as the diameter of the disk, half as broad at the base as the medullary shell.
Dimensions.—Diameter of the disk 0.12, of the medullary shell 0.04; length of the spines 0.1, breadth 0.02.
Habitat.—South Pacific, Station 300, surface.
3. Distriactis alterna, n. sp.
Disk smooth, five times as broad as the medullary shell, about twelve pores on the radius. Six marginal spines pyramidal, at equal distances, but unequal alternating size; three larger (perradial) spines as long as the shell radius, three smaller between them (interradial) half as long and broad.
Dimensions.—Diameter of the disk 0.15, of the medullary shell 0.03; length of the three major spines 0.08, of the three minor 0.05.
Habitat.—North Atlantic, Station 353, surface.
4. Distriactis palmantha, n. sp.
Disk rough, four times as broad as the medullary shell, about ten pores on the radius. Six marginal spines conical, at equal distances, but unequal alternating size; three larger (perradial) spines as long as the shell diameter, three smaller between them (interradial) as long as the radius.
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the three major spines 0.2, of the three minor 0.1,
Habitat.—South Atlantic, Station 325, surface.
5. Distriactis amphithecta, n. sp.
Disk thorny, three times as broad as the medullary shell. Six marginal spines conical, of very different size; one single (anterior) much larger than the five others, the opposite (posterior) much smaller. The other four spines are paired, the anterior pair larger than the posterior.
Dimensions.—Diameter of the disk 0.15, of the medullary shell 0.05; length of the longest spine 0.2, of the shortest 0.04, of the anterior pair 0.1, of the posterior 0.07.
Habitat.—Indian Ocean, Cocos Islands, surface, Rabbe.
Definition.—Phacodiscida with simple medullary shell and with eight radial spines on the margin of the disk (more or less regularly disposed, sometimes seven or nine).
The genus Heliosestrum (with simple medullary shell) and the following Astrosestrum (with double medullary shell) contain those Phacodiscida in which the margin of the lenticular disk bears eight radial spines, commonly more or less regularly disposed in the equatorial plane, so that the equal angles between them amount to 45°. There are, however, many exceptions to this regular eight-rayed form, either the angles between the eight spines becoming unequal or the number of the spines amounting to seven or nine (sometimes also six or ten) in one and the same species. But the regular form is as prevalent, and also in the abnormal forms indicated by the position of the spines, that we separate the genus Heliosestrum from Heliodiscus. Both genera are rich in common species, and in some of the former four perradial (larger) spines alternate regularly with four interradial (smaller) spines.
Definition.—Surface of the disk smooth, without radial spines. Bases of the marginal spines free, not connected by an equatorial girdle.
1. Heliosestrum medusinum, n. sp. (Pl. 34, fig. 6).
Heliodiscus medusinus, Haeckel, 1881, Atlas (pl. xxxiv. fig. 6).
Disk with smooth surface, four times as broad as the medullary shell. Pores regular, circular; about ten on the radius of the disk. Eight marginal spines regularly distributed (sometimes seven or nine, more or less irregular), angular, nearly pyramidal (with equilateral triangular outline), about as long and broad as the diameter of the medullary shell, without connecting equatorial girdle. From the broad base of each spine run eight to ten deep furrows convergent to its apex.
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the radial spines 0.05, basal breadth 0.05.
Habitat.—North Pacific, Station 266, surface.
2. Heliosestrum octastrum, n. sp.
Disk with smooth surface, three times as broad as the medullary shell. Pores irregular, roundish; eight to nine on the radius. Eight marginal spines regularly distributed (sometimes seven or nine, more or less irregular), conical, about as long as the diameter of the disk, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.15, of the medullary shell 0.05; length of the radial spines 0.16, basal breadth 0.01.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
3. Heliosestrum solarium, Haeckel.
Haliomma sol (partim), Ehrenberg, 1875 (non 1844), Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf. xxviii. fig. 1.
Surface of the disk smooth; its diameter six times as large as that of the medullary shell. Pores regular, circular; nine to ten on the radius. Eight marginal spines regularly distributed (sometimes seven or nine, more or less irregular), conical, about as long as the diameter of the medullary shell, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.18, of the medullary shell 0.03; length of the radial spines 0.03, basal breadth 0.01.
Habitat.—Fossil in the Tertiary rocks of Barbados.
4. Heliosestrum liriope, n. sp.
Surface of the disk smooth; its diameter four times as large as that of the medullary shell. Pores subregular, circular; seven to eight on the radius. Eight marginal spines regularly distributed, conical, compressed, alternating longer and shorter; the longer equal to the diameter of the disk, the shorter to the radius.
Dimensions.—Diameter of the disk 0.16, of the medullary shell 0.4; length of the major radial spines 0.15, of the minor 0.09.
Habitat.—North Pacific, Station 236, surface.
5. Heliosestrum quadrigeminum, n. sp.
Surface of the disk smooth; its diameter four times as large as that of the medullary shell. Pores irregular, roundish; six to seven on the radius. Eight marginal spines triangular, flat, regularly disposed, alternating longer and shorter, the major as long as the radius of the shell, and half as broad at the base, with three to four deep furrows on both sides, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.16, of the medullary shell 0.04; length of the larger radial spines 0.08, of the smaller 0.04, basal breadth 0.04.
Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.
6. Heliosestrum contiguum, Haeckel.
Haliomma contiguum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf. xxvii. fig. 5.
Disk with smooth surface, four times as broad as the medullary shell. Pores irregular, roundish, touching, with very thin bars; nine to ten on the radius. Eight marginal spines (often seven or nine) conical, half as long as the radius, twice as long as broad, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.17, of the medullary shell 0.04; length of the radial spines 0.04, basal breadth 0.02.
Habitat.—Fossil in Barbados.
7. Heliosestrum irregulare, n. sp.
Disk with smooth surface, four times as broad as the medullary shell. Pores irregular, roundish; nine to eleven on the radius. Eight conical radial spines of irregular size and distribution, often seven or nine, about as long as the radius of the disk (in some cases longer, in others shorter). No connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the radial spines 0.1, basal breadth 0.02.
Habitat.—Central Pacific, Stations 270 to 272, depth 2425 to 2925 fathoms.
Definition.—Surface of the disk armed with radial spines. Bases of the marginal spines free, without a connecting equatorial girdle.
8. Heliosestrum octonum, n. sp. (Pl. 34, fig. 3).
Disk with spiny surface, three times as broad as the medullary shell. Pores circular, of very different sizes; eight to ten on the radius. Eight conical marginal spines of equal size and equidistant, as long as the radius of the disk, and one-third as broad at the base as the medullary shell. Numerous spines on the surface bristle-shaped, on the margin half as long as the eight main spines, in the central part shorter.
Dimensions.—Diameter of the disk 0.18, of the medullary shell 0.06; length of the marginal spines 0.1, basal breadth 0.02.
Habitat.—Central Pacific, Station 271, surface.
9. Heliosestrum ægineta, n. sp.
Disk with spiny surface, four times as broad as the medullary shell. Pores irregular, roundish, of different sizes; twelve to fourteen on the radius. Eight pyramidal marginal spines regularly disposed, four larger (perradial) alternating with four smaller (interradial); the former as long as the radius of the disk, the latter half as long.
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the marginal spines 0.05 to 0.1, basal breadth 0.03.
Habitat.—South Atlantic, Station 330, surface.
Definition.—Surface of the disk smooth, without radial spines. Bases of the marginal spines connected by a solid equatorial girdle.
10. Heliosestrum octangulum, n. sp.
Disk with smooth surface, octagonal, twice as broad as the medullary shell. Pores regular, circular; nine to ten on the radius. Equatorial girdle narrow, radially striped, connecting the points of the eight short, regularly disposed, marginal spines in such a manner that the whole shell forms a regular octagon with rectilinear sides.
Dimensions.—Diameter of the disk 0.11 to 0.12, of the medullary shell 0.05 to 0.06; length of the sides of the octagon 0.06.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
11. Heliosestrum octogonium, n. sp.
Disk with smooth surface, octagonal, four times as broad as the medullary shell. Pores irregular, roundish; eight to nine on the radius. Equatorial girdle broad, smooth, connecting the points of the eight short, triangular, flat marginal spines in such a manner that the whole shell forms a subregular octagon with concave, nearly equal sides. (Sometimes seven or nine spines instead of eight are developed.)
Dimensions.—Diameter of the disk 0.16 to 0.18, of the medullary shell 0.04 to 0.05; length of the radial spines 0.02 to 0.04, basal breadth 0.03.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
12. Heliosestrum craspedotum, n. sp.
Haliomma humboldti, var., Bury, 1862, Polycystins of Barbados, pl. viii. fig. 4 (below).
Disk with smooth surface, three times as broad as the medullary shell. Pores subregular, circular; ten to twelve on the radius. Eight marginal spines (sometimes seven or nine) triangular, deeply sulcated, half as long and one-third as broad as the radius of the disk, connected by a narrow, radially striped equatorial girdle.
Dimensions.—Diameter of the disk 0.18, of the medullary shell 0.06; length of the radial spines 0.05, basal breadth 0.03.
Habitat.—Central Pacific, Stations 271 to 274, at various depths, also fossil in Barbados.
Definition.—Phacodiscida with double medullary shell and with eight radial spines on the margin of the disk (more or less regularly disposed, sometimes seven or nine).
The genus Astrosestrum differs from the foregoing Heliosestrum by the duplication of the medullary shell. The eight marginal spines in the majority of individuals are regularly formed and disposed, of equal size and equidistant. But there are frequent exceptions to this rule, either the angles between the eight spines being more or less different, or the number amounting to seven or nine, instead of eight. Here also in some species four larger (perradial) spines alternate regularly with four smaller (interradial spines), after the same law of symmetry, which is common in the Medusæ.
Definition.—Surface of the disk smooth, without radial spines. Bases of the marginal spines free, not connected by an equatorial girdle.
1. Astrosestrum ephyra, n. sp. (Pl. 32, figs. 4, 4a).
Disk with smooth surface, three times as broad as the outer and nine times as broad as the inner medullary shell. Pores subregular, circular; seven to eight on the radius of the disk. Eight marginal spines (sometimes seven or nine) more or less irregularly disposed, of variable size, commonly as long as the radius of the disk, twice as long as broad, pyramidal, sulcate, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.12, of outer medullary shell 0.04, of the inner 0.014; length of the marginal spines 0.05 to 0.07, basal breadth 0.03.
Habitat.—Central Pacific, Stations 270 to 274, depths 2350 to 2925 fathoms.
2. Astrosestrum nauphanta, n. sp. (Pl. 32, fig. 5).
Disk with smooth surface, two and a half times as broad as the outer and five times as broad as the inner medullary shell. Pores regular, circular; eight to nine on the radius of the disk. Eight marginal spines (often seven or nine) more or less regularly disposed, of equal size, half as long as the radius of the disk, and quite as broad at the base, compressed triangular, sulcate, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.15, of the outer medullary shell 0.06, of the inner 0.03; length of the marginal spines 0.04, basal breadth 0.04.
Habitat.—Pacific, central area, Stations 266 to 268, depth 2700 to 2900 fathoms.
3. Astrosestrum octacanthum, Haeckel.
Haliomma octacanthum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 295, Taf. viii. fig. 11.
Disk with smooth surface, twice as broad as the outer and six times as broad as the inner medullary shell. Pores regular, circular; six to seven on the radius of the disk. Eight marginal spines regularly disposed, of variable size, the longest as long as the radius, pyramidal, not broader at the base than one pore, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.12, of the outer medullary shell 0.06, inner 0.02; length of the marginal spines 0.03 to 0.06, basal breadth 0.01.
Habitat.—Western Pacific, Philippine Sea, 3300 fathoms, Ehrenberg; Station 225, depth 4475 fathoms.
4. Astrosestrum acraspedum, n. sp.
Disk with smooth surface, three times as broad as the outer and six times as broad as the inner medullary shell. Pores regular, circular; nine to ten on the radius of the disk. Eight marginal spines regularly disposed, of alternating size; four major (perradial) spines as long as the diameter of the disk, four minor (interradial) half as long; spines cylindrical, not broader at the base than one pore, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.2, of the outer medullary shell 0.07, of the inner 0.035; length of the larger spines 0.2, of the smaller 0.1, basal breadth 0.01.
Habitat.—South Atlantic, Station 332, depth 2200 fathoms.
Definition.—Surface of the disk covered with radial spines. Bases of the marginal spines free, not connected by an equatorial girdle.
5. Astrosestrum acanthastrum, n. sp.
Disk with spiny surface, three times as broad as the outer and nine times as broad as the inner medullary shell. Pores subregular, circular; ten to eleven on the radius. Eight marginal spines (sometimes seven or nine) regularly disposed, triangular, about half as long as the radius of the disk, and one-third as broad at the base, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.18, of the outer medullary shell 0.06, of the inner 0.02; length of the radial spines 0.05, basal breadth 0.03.
Habitat.—North Atlantic, Gulf Stream, Færöe Channel, surface, John Murray.
6. Astrosestrum echinastrum, n. sp.
Disk with spiny surface, twice as broad as the outer and four times as broad as the inner medullary shell. Pores irregular, roundish; eight to nine on the radius. Eight marginal spines more or less regularly disposed, pyramidal, nearly as long as the radius of the disk, and not broader at the base than one large pore, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.15, of the outer medullary shell 0.07, of the inner 0.04; length of the radial spines 0.07, basal breadth 0.01.
Habitat.—Fossil in the Tertiary rocks of Sicily, Caltanisetta, Teuscher.
Definition.—Surface of the disk smooth, without radial spines. Bases of the marginal spines connected by a solid equatorial girdle.
7. Astrosestrum pelagia, n. sp.
Disk with smooth surface, three times as broad as the outer and eight times as broad as the inner medullary shell. Pores regular, circular; eight to nine on the radius. Eight marginal spines conical, about as long as the radius of the disk, of nearly equal length, one-third as broad at the base, connected by a radially striped equatorial girdle.
Dimensions.—Diameter of the disk 0.18, of the outer medullary shell 0.06, of the inner 0.023; length of the radial spines 0.09, basal breadth 0.03.
Habitat.—Indian Ocean, Ceylon, Haeckel, surface.
8. Astrosestrum floscula, n. sp.
Disk with smooth surface, two and a half times as broad as the outer and five times as broad as the inner medullary shell. Pores irregular, roundish; ten to eleven on the radius. Eight marginal spines triangular, plain, scarcely half as long as the radius of the disk, nearly as broad at the base, connected by an even equatorial girdle.
Dimensions.—Diameter of the disk 0.2, of the outer medullary shell 0.08, of the inner 0.04; length of the radial spines 0.09, basal breadth 0.07.
Habitat.—South Atlantic, Station 325, surface.
Definition.—Phacodiscida with a variable number of radial spines on the margin of the disk (ten to twenty or more), which are commonly more or less irregular (sometimes regularly formed and disposed).
Definition.—Phacodiscida with simple medullary shell and with numerous (ten to twenty or more) simple radial spines on the margin of the disk (commonly with a variable number and an irregular disposition of the undivided spines).
The genus Heliodiscus, the most common and polymorphic of all Phacodiscida, was founded by me in 1862 as the first known type of this family (loc. cit.). I use here the diagnosis of this genus in a restricted sense, including only the species, in which the number of marginal spines amounts to ten, twenty, or more (sometimes fifty to eighty, rarely more than one hundred). The number of spines is in the different species variable, and their disposition commonly more or less irregular, whilst in the preceding genera (with two, three, four, six, or eight marginal spines) their distance and form are commonly regular.
Definition.—Surface of the disk smooth, without radial spines. Bases of the marginal spines free, without a connecting equatorial girdle.
1. Heliodiscus asteriscus, n. sp. (Pl. 33, fig. 8).
Disk with smooth surface, three times as broad as the medullary shell. Pores regular, circular; ten to twelve on the radius of the disk. Marginal spines fifteen to twenty, conical, often double contoured, of variable size and disposition, the largest as long as the radius of the disk, as broad at the base as one pore.
Dimensions.—Diameter of the disk 0.15, of the medullary shell 0.05; length of the radial spines 0.04 to 0.07, basal breadth 0.01.
Habitat.—Cosmopolitan; Mediterranean (Corfu), Indian Ocean (Madagascar), Atlantic and Pacific, many Stations, surface and various depths.
2. Heliodiscus trochiscus, n. sp. (Pl. 34, figs. 10, 13).
Disk with smooth surface, four times as broad as the medullary shell. Pores regular, circular; fourteen to sixteen on the radius. Marginal spines twelve to sixteen, conical, of variable size and disposition, the largest as long as the diameter of the medullary shell, twice as broad as one pore.
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the radial spines 0.01 to 0.025, basal breadth 0.005.
Habitat.—Central Pacific, Stations 272 to 274, surface.
3. Heliodiscus trigonodon, n. sp.
Disk with smooth surface, four times as broad as the medullary shell. Pores regular, circular; eighteen to twenty on the radius. Marginal spines sixteen to twenty, equilateral triangular, flat, smooth, about as long and broad as the radius of the medullary shell.
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the radial spines 0.03, basal breadth 0.03.
Habitat.—Central Pacific, Stations 266 to 274, depths 2350 to 2925 fathoms.
4. Heliodiscus glyphodon, n. sp. (Pl. 35, fig. 2).
Heliosestrum glyphodon, Haeckel, 1881, Prodromus et Atlas (pl. xxxv. fig. 2).
Disk with smooth surface, four times as broad as the medullary shell. Pores subregular, circular; seven to eight on the radius. Marginal spines ten to twelve, equilateral triangular, flat, deeply furrowed, twice as long as broad, and as long as the radius of the disk.
Dimensions.—Diameter of the disk 0.14, of the medullary shell 0.035; length of the radial spines 0.07, basal breadth 0.035.
Habitat.—North Pacific, Station 253, depth 3125 fathoms.
5. Heliodiscus helianthus, Haeckel.
Haliomma helianthus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf. xxvii. fig. 1.
Disk with smooth surface, five times as broad as the medullary shell. Pores regular, oblong, disposed regularly in sixty to eighty radial series; fourteen to sixteen on the radius. Marginal spines sixty to eighty, conical, about as long as the diameter of the medullary shell, twice as broad as one pore.
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.04; length of the radial spines 0.04, basal breadth 0.005.
Habitat.—Fossil in Barbados.
6. Heliodiscus sol, Haeckel.
Haliomma sol, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 52.
Heliodiscus sol, Haeckel, 1862, Monogr. d. Radiol., p. 438.
Disk with smooth surface, four times as broad as the medullary shell. Pores irregular, roundish; eight to ten on the radius. Marginal spines twenty to thirty, conical, the largest as long as the radius of the medullary shell, their bases widely distant. (The species from Barbados figured by Ehrenberg, 1875, as Haliomma sol, appertains to Heliosestrum solare.)
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the radial spines 0.02 to 0.025, basal breadth 0.01.
Habitat.—Fossil in Tertiary rocks of Greece (Ægina), Ehrenberg.
7 Heliodiscus siculus, Stöhr.
Heliodiscus siculus, Stöhr, 1880, Palæontogr., vol. xxvi. p. 89, Taf. i. fig. 14.
Disk with smooth surface, three times as broad as the medullary shell. Pores irregular roundish; seven to eight on the radius. Marginal spines forty to fifty, conical, very irregular, the largest as long as the radius of the medullary shell, their bases coming in contact.
Dimensions.—Diameter of the disk 0.13 to 0.15, of the medullary shell 0.04 to 0.05; length of the radial spines 0.02 to 0.03, basal breadth 0.002 to 0.006.
Habitat.—Fossil in Tertiary rocks of Sicily, Grotte (Stöhr), Caltanisetta (Teuscher).
8. Heliodiscus polymorphus, n. sp. (Pl. 34, figs. 11, 12).
Disk with smooth surface, four times as broad as the medullary shell. Pores irregular, roundish; ten to twelve on the radius. Marginal spines ten to fifteen, pyramidal, angular, very irregular and variable in size and distribution, the largest nearly as long as the diameter of the disk, as broad at the base as the radius of the medullary shell.
Dimensions.—Diameter of the disk 0.15 to 0.2, of the medullary shell 0.04 to 0.05; length of the radial spines 0.06 to 0.18, basal breadth 0.02 to 0.03.
Habitat.—Central Pacific, Stations 265 to 268, depths 2700 to 2900 fathoms.
9. Heliodiscus solaster, n. sp. (Pl. 34, fig. 4).
Disk with smooth surface, three times as broad as the medullary shell. Pores subregular, roundish; nine to ten on the radius. Marginal spines fifty to sixty, cylindro-conical, flexuose, very variable in size, the largest nearly as long as the diameter of the disk. The spines lie not only in the equatorial plane (as usual), but also in two to four crowded girdles on both sides of it.
Dimensions.—Diameter of the disk 0.15, of the medullary shell 0.05; length of the radial spines 0.05 to 0.15, basal breadth 0.008.
Habitat.—Indian Ocean, Madagascar, Rabbe, surface.
Definition.—Surface of the disk covered with radial spines. Bases of the marginal spines free, without a connecting equatorial girdle.
10. Heliodiscus phacodiscus, Haeckel.
Heliodiscus phacodiscus, Haeckel, 1862, Monogr. d. Radiol., p. 437, Taf. xvii. figs. 5-7.
Haliomma phacodiscus, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 815.
Disk with spiny surface, three times as broad as the medullary shell. Pores regular, circular; six to eight on the radius. Marginal spines twelve to sixteen, conical, as long as the radius of the disk, and one-third as broad as the diameter of the medullary shell.
Dimensions.—Diameter of the disk 0.12 to 0.16, of the medullary shell 0.04 to 0.05; length of the marginal spines 0.06 to 0.08, basal breadth 0.01 to 0.02.
Habitat.—Mediterranean (Messina), Canary Islands (Lanzerote).
11. Heliodiscus amphidiscus, Haeckel.
Heliodiscus amphidiscus, Haeckel, 1862, Monogr. d. Radiol., p. 437.
Haliomma amphidiscus, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 154, Taf. ii. figs. 3-7.
Disk with spiny surface, three times as broad as the medullary shell. Pores regular, circular; eight to ten on the radius. Marginal spines twelve to fifteen, bristle-shaped, not larger than the surface spines, about as long as the radius of the medullary shell.
Dimensions.—Diameter of the disk 0.16, of the medullary shell 0.05; length of the marginal spines 0.03, basal breadth 0.002.
Habitat.—Mediterranean (south shore of France), J. Müller.
12. Heliodiscus echiniscus, n. sp. (Pl. 34, fig. 5).
Disk with spiny surface, three times as broad as the medullary shell. Pores irregular, roundish or polygonal; eight to ten on the radius. Marginal spines thirty to fifty, pyramidal, angular, of very variable size, number, and disposition, gradually passing into the surface-spines; the largest nearly as long as the diameter of the medullary shell.
Dimensions.—Diameter of the disk 0.14, of the medullary shell 0.045; length of the radial spines 0.02 to 0.04, basal breadth 0.006.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
13. Heliodiscus pertusus, n. sp. (Pl. 35, fig. 1).
Heliosestrum pertusum, Haeckel, 1881, Prodromus et Atlas (pl. xxxv. fig. 1).
Disk with spiny surface, three times as broad as the medullary shell. Pores irregular, circular, hexagonally framed; eight to ten on the radius. Marginal spines ten to thirty, very variable in size and disposition; commonly eight to twelve larger spines, which are pyramidal, about as long as the radius of the disk and perforated by two to four irregular, longish pores. Between these fenestrated large spines are commonly ten to twenty smaller conical spines, gradually passing into those of the surface.
Dimensions.—Diameter of the disk 0.13 to 0.16, of the medullary shell 0.04 to 0.05; length of the marginal spines 0.04 to 0.08, basal breadth 0.01 to 0.015.
Habitat.—North Pacific, Stations 241 to 244, depths 2300 to 2900 fathoms.
Definition.—Surface of the disk smooth, without radial spines. Bases of the marginal spines connected by a solid equatorial girdle.
14. Heliodiscus cingillum, n. sp. (Pl. 33, fig. 7).
Disk with smooth surface, five times as broad as the medullary shell. Pores regular, circular; twelve to fourteen on the radius. Equatorial girdle about as broad as the medullary shell, in the proximal half radially striped, on the margin with twenty to twenty-four short, flat, triangular spines, which are shorter than the breadth of the girdle.
Dimensions.—Diameter of the disk 0.25, of the medullary shell 0.05; length of the marginal spines 0.02, basal breadth 0.02.
Habitat.—Central Pacific, Station 274, depth 2750 fathoms.
15. Heliodiscus humboldti, Haeckel.
Heliodiscus humboldti, Haeckel, 1862, Monogr. d. Radiol., p. 438.
Haliomma humboldti, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 27; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxvii. fig. 3.
Haliomma humboldti, Bury, 1862, Polycystins of Barbados, pl. viii. fig. 3 (at left).
Disk with smooth surface, four times as broad as the medullary shell. Pores regular, circular; eighteen to twenty on the radius. Equatorial girdle half as broad as the medullary shell, in the proximal half radially striped, on the margin with sixteen to twenty short, flat, triangular teeth, which are longer than the breadth of the girdle.
Dimensions.—Diameter of the disk 0.12 to 0.2, of the medullary shell 0.03 to 0.05; length of the marginal spines 0.02 to 0.04, basal breadth 0.02.
Habitat.—Fossil in Barbados (common and very variable).
16. Heliodiscus marginatus, n. sp. (Pl. 34, fig. 9).
Disk with smooth surface, three times as broad as the medullary shell. Pores regular, circular; nine to ten on the radius. Equatorial girdle one-fourth to one-half as broad as the medullary shell, in the whole breadth radially striped, on the margin with twelve to eighteen very short and broad, triangular, marginal spines.
Dimensions.—Diameter of the disk 0.15 to 0.2, of the medullary shell 0.05 to 0.06; length of the marginal spines 0.01 to 0.02, basal breadth 0.02.
Habitat.—Central Pacific, Stations 265 to 268, depth 2900 fathoms.
17. Heliodiscus sulcatus, n. sp.
Disk with smooth surface, four times as broad as the medullary shell. Pores subregular, circular; twelve to fifteen on the radius. Equatorial girdle as broad as the medullary shell, in the whole breadth radially striped on the margin with ten to fifteen triangular, deeply sulcated teeth, about as long and broad as the medullary shell. (Similar to Heliodiscus glyphodon, Pl. 35, fig. 2, but with broad sulcated girdle and shorter, more numerous spines.)
Dimensions.—Diameter of the disk 0.15 to 0.2, of the medullary shell 0.04 to 0.05; length of the radial spines 0.05 to 0.06, basal breadth 0.04 to 0.05.
Habitat.—Atlantic and Pacific, tropical part, many Stations, surface.
18. Heliodiscus umbonatus, Haeckel.
Haliomma umbonatum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf. xxvii. fig. 4.
Disk with smooth surface, three times as broad as the medullary shell. Pores irregular, roundish; eight to ten on the radius. Equatorial girdle half as broad as the medullary shell, hyaline, not radially striped, on the margin with ten to twenty triangular, irregular, smooth teeth, very variable in size and disposition.