_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, 4_a_).
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 {443}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.
Subgenus 2. _Astrosestilla_, Haeckel.
_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.
{444}Subgenus 3. _Astrosestomma_, Haeckel.
_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.
Subfamily 3. HELIODISCIDA, Haeckel, 1881, Prodromus, p. 457.
_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).
Genus 193. _Heliodiscus_,[232] Haeckel, 1862, Monogr. d. Radiol., p. 436.
_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 {445}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.
Subgenus 1. _Heliodiscetta_, Haeckel.
_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.
{446}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).
{447}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.
Subgenus 2. _Heliodiscilla_, Haeckel.
_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.
{448}_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.
Subgenus 3. _Heliodiscomma_, Haeckel.
_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.
{449}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.
{450}_Dimensions._--Diameter of the disk 0.15 to 0.2, of the medullary
shell 0.05 to 0.06; length of the marginal spines 0.02 to 0.08, basal
breadth 0.01 to 0.03.
_Habitat._--Cosmopolitan; Atlantic, Pacific, in various depths; also fossil
in Barbados and Sicily.
Subgenus 4. _Heliodiscura_, Haeckel.
_Definition._--Surface of the disk covered with radial spines. Bases of the
marginal spines connected by a solid equatorial girdle.
19. _Heliodiscus apollinis_, n. sp.
Disk with spiny or bristly surface, three times as broad as the medullary
shell. Pores regular, circular; eleven to twelve on the radius. Equatorial
girdle narrow, on the margin with sixteen to twenty broad, flat, triangular
teeth, which are half as long and one-fourth as broad as the medullary
shell. (Very similar to _Astrophacus apollinis_, Pl. 32, fig. 2, but with
simple medullary shell.)
_Dimensions._--Diameter of the disk 0.18, of the medullary shell 0.06;
length of the marginal spines 0.03, basal breadth 0.015.
_Habitat._--Mediterranean (Corfu), Haeckel, surface.
20. _Heliodiscus zoroaster_, n. sp.
Disk with spiny surface, four times as broad as the medullary shell. Pores
subregular, circular; fourteen to sixteen on the radius. Equatorial girdle
broad, radially striped, on the margin with ten to twelve pyramidal, deeply
sulcated radial spines, which are nearly as long as the radius of the disk,
and one-fourth as broad at the base.
_Dimensions._--Diameter of the disk 0.24, of the medullary shell 0.06;
length of the marginal spines 0.11, basal breadth 0.03.
_Habitat._--Indian Ocean, between Aden and Ceylon, Haeckel, surface.
Genus 194. _Heliodrymus_,[233] Haeckel, 1881, Prodromus, p. 457.
_Definition._--#Phacodiscida# with simple medullary shell and with numerous
(ten to twenty or more) branched radial spines on the margin of the disk
(commonly with a variable number and an irregular disposition of the
ramified spines).
The genus _Heliodrymus_ differs from the nearly allied _Heliodiscus_ by the
ramification of the marginal spines, a character hitherto observed in no
other genus of Phacodiscida. The branching is more or less irregular,
either a simple bifurcation or a repeated fissure; the spines and their
branches are commonly more or less flexuose. {451}We can distinguish two
subgenera: in _Heliocladus_ the surface of the disk is smooth, in
_Heliodendrum_ covered with bristle-shaped radial spines, which are either
simple or also branched, sometimes longer than the thick marginal spines.
Subgenus 1. _Heliocladus_, Haeckel, 1881, Prodromus, p. 457.
_Definition._--Surface of the disk smooth, without radial spines.
1. _Heliodrymus dendrocyclus_, n. sp. (Pl. 33, fig. 9).
_Heliocladus dendrocyclus_, Haeckel, 1881, Prodromus et Atlas (pl.
xxxiii. fig. 9).
Disk with smooth surface, three times as broad as the medullary shell.
Pores regular, circular, hexagonally framed; eight to nine on the radius.
Marginal spines sixteen to twenty, cylindrical, very strong, flexuose,
irregularly branched, nearly as long as the diameter of the disk. Between
these main spines, each of which bears two to six irregular branches, are
scattered on the margin numerous smaller simple spines.
_Dimensions._--Diameter of the disk 0.16, of the medullary shell 0.05;
length of the main spines 0.1 to 0.14, breadth 0.01 to 0.02.
_Habitat._--Central Pacific, Station 271, surface.
2. _Heliodrymus furcatus_, n. sp.
Disk with smooth surface, four times as broad as the medullary shell. Pores
irregular, roundish; ten to twelve on the radius. Marginal spines twenty to
twenty-five, cylindrical, flexuose, forked, about as long as the radius of
the disk; fork-branches irregular, of unequal size. Some smaller simple
spines are scattered between the forked ones.
_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.04;
length of the radial spines 0.07 to 0.09, breadth 0.01.
_Habitat._--Central Pacific, Station 265, surface.
3. _Heliodrymus grottensis_, Haeckel.
_Heliodiscus grottensis_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 89,
Taf. i. fig. 13.
Disk with smooth surface, two and a half times as broad as the medullary
shell. Pores irregular, roundish; eight to nine on the radius. Marginal
spines twenty to thirty, conical, very irregular in form, size, and
disposition; the smaller simple, the larger irregularly branched and half
as long as the radius of the disk.
_Dimensions._--Diameter of the disk 0.17, of the medullary shell 0.07;
length of the marginal spines 0.02 to 0.04, basal breadth 0.01 to 0.02.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
{452}Subgenus 2. _Heliodendrum_, Haeckel.
_Definition._--Surface of the disk armed with simple or branched radial
spines.
4. _Heliodrymus setosus_, n. sp.
Disk with spiny surface, four times as broad as the medullary shell. Pores
regular, circular; twelve to thirteen on the radius. Marginal spines ten to
twelve, cylindrical, irregularly branched, each with two to eight flexuose
branches of different sizes; the largest as long as the diameter of the
disk. Spines of the surface bristle-shaped, half as long, not branched.
_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05;
length of the marginal spines 0.12 to 0.18, breadth 0.025.
_Habitat._--North Pacific, Station 254, surface.
5. _Heliodrymus ramosus_, n. sp. (Pl. 35, figs. 3, 4).
Disk with spiny surface, three times as broad as the medullary shell. Pores
regular, circular, hexagonally framed; eleven to twelve on the radius.
Marginal spines sixteen to twenty, cylindrical, about as long as the
radius, irregularly forked or branched, with unequal flexuose branches.
Spines of the surface nearly as long, bristle-shaped, also irregularly
branched.
_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.05;
length of the spines 0.06 to 0.08, basal breadth 0.01 to 0.015.
_Habitat._--South Pacific, Station 288, surface.
6. _Heliodrymus viminalis_, n. sp. (Pl. 35, fig. 5).
Disk with spiny surface, two and a half times as broad as the medullary
shell. Pores irregular, roundish; ten to twelve on the radius. Marginal
spines fifteen to twenty, cylindro-conical, strong, partly simple, partly
forked, about as long as the diameter of the disk. Spines of the surface
very numerous, bristle-shaped, longer than the marginal spines, and more
branched.
_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.06;
length of the marginal spines 0.11 to 0.14, basal breadth 0.01 to 0.015;
length of the surface spines 0.2 to 0.03.
_Habitat._--Central Pacific, Station 271, surface.
Genus 195. _Astrophacus_,[234] Haeckel, 1881, Prodromus, p. 457.
_Definition._--#Phacodiscida# with double 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 _Astrophacus_ differs from the similar _Heliodiscus_ in the
duplication of the medullary shell. The number and disposition of the
radial spines of the margin {453}(commonly between ten and twenty) is also
here variable in one and the same species. The greater number of observed
species of _Astrophacus_ resemble in a very remarkable manner the
corresponding species of _Heliodiscus_, and differ only in the double
medullary shell.
Subgenus 1. _Astrophacetta_, Haeckel.
_Definition._--Surface of the disk smooth, without radial spines. Bases of
the marginal spines free, without a connecting equatorial girdle.
1. _Astrophacus asteriscus_, 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; twelve to
fourteen on the radius. Marginal spines fifteen to twenty, of variable size
and disposition; the largest as long as the radius of the disk, as broad at
the base as one pore. (Very similar to _Heliodiscus asteriscus_, Pl. 33,
fig. 8, but differing in the double medullary shell.)
_Dimensions._--Diameter of the disk 0.2, of the outer medullary shell 0.07,
of the inner 0.025; length of the marginal spines 0.05 to 0.1, basal
breadth 0.01.
_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.
2. _Astrophacus trochiscus_, n. sp. (Pl. 34, fig. 14).
Disk with smooth surface, three times as broad as the outer and seven times
as broad as the inner medullary shell. Pores irregular, roundish; twelve to
thirteen on the radius. Marginal spines sixteen to twenty, conical, of
irregular variable size and disposition; the largest as long as the inner
medullary shell. (Differs from _Heliodiscus trochiscus_ in the double
medullary shell.)
_Dimensions._--Diameter of the disk 0.22, of the outer medullary shell
0.08, of the inner 0.03.
_Habitat._--North Atlantic, Station 354, surface.
3. _Astrophacus solaris_, n. sp. (Pl. 32, fig. 1).
Disk with smooth surface, three times as broad as the outer and seven times
as broad as the inner medullary shell. Pores subregular, roundish; twelve
to fourteen on the radius. Marginal spines one hundred to one hundred and
twenty, conical, flexuose, of irregular size and form; the largest
one-third as long as the diameter of the disk. The spines lie not only in
the equatorial plane (as is usual) but also in two to four crowded girdles
on both sides of it. (Very similar to _Heliodiscus solaster_, Pl. 34, fig.
4, but of double the size, with double the number of spines and with a
double medullary shell.)
_Dimensions._--Diameter of the disk 0.3, of the outer medullary shell 0.11,
of the inner 0.045; length of the spines 0.03 to 0.1, basal breadth 0.01 to
0.02.
_Habitat._--Indian Ocean, Sunda Strait, Rabbe, surface.
{454}Subgenus 2. _Astrophacilla_, Haeckel.
_Definition._--Surface of the disk covered with radial spines. Bases of the
marginal spines free, without a connecting equatorial girdle.
4. _Astrophacus phacodiscus_, n. sp. (Pl. 32, fig. 3).
Disk with spiny surface, two and a half times as broad as the outer and
seven times as broad as the inner medullary shell. Pores subregular,
circular; ten to twelve on the radius. Marginal spines twelve to sixteen,
conical, stout, nearly as long as the radius of the disk, and as broad at
the base as the inner medullary shell. The numerous bristle-shaped spines
of the surface are scarcely half as long. (Similar to _Heliodiscus
phacodiscus_, Haeckel, Monogr. d. Radiol., Taf. xvii. figs. 5-7, but
differing in the double medullary shell.)
_Dimensions._--Diameter of the disk 0.18, of the outer medullary shell
0.07, of the inner 0.025; length of the marginal spines 0.08 to 0.09, basal
breadth 0.03.
_Habitat._--South Pacific, Station 300, surface.
Subgenus 3. _Astrophacomma_, Haeckel.
_Definition._--Surface of the disk smooth, without radial spines. Bases of
the marginal spines connected by a solid equatorial girdle. (Perhaps =
_Chilomma_(?) Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss.
Berlin, p. 54.)
5. _Astrophacus cingillum_, n. sp.
_Haliomma humboldti_, var., Bury, 1862, Polycystins of Barbados, pl.
viii. fig. 3 (at right).
Disk with smooth surface, three times as broad as the outer and eight times
as broad as the inner medullary shell. Pores regular, circular; eleven to
thirteen on the radius. Equatorial girdle about as broad as the inner
medullary shell, in the proximal half radially striped, on the margin with
eighteen to twenty-four short, flat, triangular spines, about as long as
the breadth of the girdle. (Similar to _Heliodiscus cingillum_, but with
double medullary shell.)
_Dimensions._--Diameter of the disk 0.2, of the outer medullary shell 0.07,
of the inner 0.025; length of the spines 0.02, basal breadth 0.02.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms; also
fossil in Barbados.
6. _Astrophacus saturnus_, Haeckel.
? _Chilomma saturnus_, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 297; 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 286,
Taf. ii. fig. 5.
? _Chilomma saturnus_, Haeckel, 1862, Monogr. d. Radiol., p. 447.
Disk with smooth surface, two and a half times as broad as the outer, six
times as broad as the inner medullary shell. Pores large, irregular,
roundish; five to seven on the radius (?). Equatorial girdle very broad,
radially striped, nearly as broad as the outer medullary shell, perforated
by {455}twenty to thirty (or more?) radial spines. (The position of this
species, and the identity of _Chilomma_ with _Astrophacomma_, remains
doubtful, as the imperfect figure given by Ehrenberg of _Chilomma
saturnus_, the only species of the genus, is in contradiction with his
vague description, as is very often the case.)
_Dimensions._--Diameter of the disk 0.12 (with girdle 0.22) of the outer
medullary shell 0.05, of the inner 0.02.
_Habitat._--Arctic Ocean (Greenland, depth 1000 fathoms), Ehrenberg.
Subgenus 4. _Astrophacura_, Haeckel.
_Definition._--Surface of the disk covered with radial spines. Bases of the
marginal spines connected by a solid equatorial girdle.
7. _Astrophacus apollinis_, n. sp. (Pl. 32, fig. 2).
Disk with spiny surface, three times as broad as the outer, eight times as
broad as the inner medullary shell. Pores regular, circular; eleven to
twelve on the radius of the disk. Equatorial girdle narrow, smooth, on the
margin with twelve to sixteen broad, flat, triangular spines, of the same
length as the numerous bristle-shaped spines of the surface, which reach
half the radius of the disk. (Very similar to _Heliodiscus apollinis_, but
differing in the double medullary shell.)
_Dimensions._--Diameter of the disk 0.24, of the outer medullary shell
0.08, of the inner 0.03; length of the radial spines 0.06, basal breadth
0.03.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.
Family XX. #COCCODISCIDA#, Haeckel (Pls. 36-38).
_Coccodiscida_, Haeckel, 1862, Monogr. d. Radiol., p. 485.
_Coccodiscida_, Haeckel, 1881, Prodromus, p. 458.
_Lithocyclidina_, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 214 (_partim_).
_Definition._--#Discoidea# with extracapsular phacoid shell (or lenticular
latticed cortical shell), connected by radial beams with an intracapsular,
simple or double, concentric medullary shell, and surrounded by one or more
concentric chambered equatorial girdles on the margin.
The family #Coccodiscida# was founded by me in 1862 for those #Discoidea#
which agree with the Phacodiscida in the formation of the lenticular
"phacoid shell" (including a simple or double medullary shell), but differ
from them in the development of peculiar concentric chambered rings or
girdles around the equatorial margin of the disk, similar to those of the
Porodiscida.
The Coccodiscida represent a polymorphic family, in which we here
distinguish sixteen genera with fifty-seven species; it comprises the
greater part of those {456}#Discoidea# which Ehrenberg united in his group
Lithocyclidina (1875, represented by four genera and eight species);
several of these, however, appertain to quite different families, as his
_Astromma entomocora_, _Lithocyclia amphitrites_, &c. His knowledge of the
structure was very imperfect. The peculiar differentiation of the genera
and species exhibits the greatest analogy to that of the following family,
Porodiscida, though the structure of the central disk in both families is
quite different.
_The Phacoid Shell_, or the circular, lenticular cortical shell exhibits in
the Coccodiscida quite the same structure and composition as in the
Phacodiscida, described above (p. 420), so that there can be no doubt as to
the phylogenetic origin of the former from the latter. Quite in the same
way in both families, the lenticular "phacoid shell" is connected by
numerous, short, radial beams with the intracapsular, simple or double,
medullary shell; and also here these beams are commonly disposed in two
groups around the poles of the shortened main axis of the lens, so that
their distal ends are implanted in both circumpolar areas (Pl. 36, figs.
2-6; Pl. 37, figs. 3, 7; Pl. 38, figs. 2, 7). The medullary shell is
commonly simple, spherical, sometimes a little lenticularly compressed;
more rarely it is double, composed of two concentric lattice-shells, which
are connected by radial beams; in this case either both concentric
medullary shells are spherical, or the inner is spherical, and the outer
lenticular, very rarely the inner is lenticular also. In average size and
structure they agree perfectly with those of the Phacodiscida.
_The Chamber Girdles_ or "chambered rings" around the equatorial margin of
the disk, which constitute the only difference between the Coccodiscida and
the Phacodiscida, seem to exhibit a considerable degree of difference of
structure in the numerous species of this family; but I regret that I
cannot explain them here satisfactorily. The study of these structures is
extremely difficult because of the thickness and darkness of the massive
opaque shells; to get a perfect knowledge of them, it is indispensable to
compare slides made in different directions (horizontal slides through the
equatorial and parallel planes, vertical slides through radial and parallel
planes, oblique slides in different directions). But this requires a long
time and a most careful study of the slides, which are very difficult to
get in satisfactory condition. Therefore the following remarks can have
only a provisional value.
In all Coccodiscida we can distinguish on the equatorial chamber-girdle of
the lens-margin (even on superficial inspection) three different elements
of structure, viz.:--(A) concentric circular rings in the equatorial plane;
(B) numerous radial beams piercing the former and dividing them into
imperfect chambers; (C) porous plates or sieve-plates on both convex faces
of the disk. The probable morphological significance of these three
elements is the following:--Each ring or girdle corresponds to an outer
lenticular cortical shell, which is only developed on the marginal part,
whilst its central part is represented by the phacoid shell. Therefore the
radial beams (separating the imperfect chambers) are the same as in the
concentric Polysphærida, and the {457}sieve-plates of the surface are the
porous walls of the cortical shell itself. The correctness of this
explanation seems to be proved by such forms as figured in Pl. 38, figs. 2,
4, where the whole surface of the phacoid shell is covered by a concentric
chamber-work, as a central continuation of the marginal concentric rings.
If we imagine a system of perfect concentric lenticular phacoid shells,
compressed strongly from both poles of the shortened main axis, we get the
same figure.
Rarely one single girdle only is developed on the equatorial margin of the
lenticular disk (Pl. 37, figs. 2, 3, 5). Commonly the number of concentric
girdles amounts to three to six, often to ten to twelve or more. Some of
these largest Coccodiscida reach a considerable size. Commonly all girdles
are of the same breadth, which is about equal to the radius or to the
diameter of the inner medullary shell. Rarely the first (or innermost)
girdle differs by its greater breadth from the succeeding ones (Pl. 36,
fig. 8).
Only in few Coccodiscida the girdle-building remains restricted to the
equatorial planes, so that all the chambers lie in it. Commonly on both
sides of this plane become developed several layers, and often the number
of these (three to six or more) increases towards the periphery; in other
cases not their number, but their height increases. Therefore very often
the margin of the discoidal shell is much thickened, as thick as the centre
of the lenticular phacoid shell (or even more); whilst between the latter
and the former (on the proximal girdles) the disk is considerably thinner
(Pl. 36, figs. 2, 4; Pl. 37, figs. 7, 8; Pl. 38, figs. 2, 4). The
stratified layers communicate by large openings between their chambers. The
radial beams are commonly more or less regular and piercing, but also
frequently irregular and interrupted; often their number increases towards
the margin by intercalation of new beams.
_The Pores_ of the sieve-plates, which cover both sides of the chambered
disk, appear on the margin of the phacoid shell as direct continuations of
the pores of the latter, and sometimes they are so regularly disposed that
one single circular pore is situated on the surface of each chamber (Pl.
36, fig. 7; Pl. 37, fig. 1). But commonly the pores are of variable size
and number, two to three on each chamber, and often quite irregularly
scattered.
_The Margin_ of the chambered disk exhibits many differences, which afford
characters for the distinction of genera. In the first subfamily, the
Lithocyclida, the margin is quite simple without radial appendages. In the
second subfamily, the Stylocyclida, it is armed with solid radial spines
lying in the equatorial plane, and often regularly disposed in the same
manner as in the Phacodiscida (compare above, p. 421). In the third
subfamily, the Astracturida, the margin bears two or more (commonly three
or four) chambered arms, also situated in the plane of the disk, and of the
same structure as the circular chambered girdles (Pl. 38). In some cases
even the whole system of chamber-girdles is represented only by the radial
arms, which are inserted immediately on the margin of the phacoid shell. We
may regard therefore these formations as imperfect chambered disks, which
are developed only in the direction of certain rays {458}(perradii), and
reduced in the direction of the alternating rays (interradii). In some
Astracturida the chambered arms exhibit a structure different from the more
irregular chamber-work between them, so that we can distinguish the latter,
connecting the arms like a web-membrane, as a peculiar "patagium" (as in
many Porodiscida) (Pl. 38, figs. 8, 9). Often the distal ends of the
chambered arms are armed with a radial spine (Pl. 38, figs. 5, 6, 9).
_The Central Capsule_ of the Coccodiscida is originally always of the same
form and shape as in their ancestral group, the Phacodiscida; a circular
lenticular disk, which envelops the simple or double medullary shell and is
enclosed by the cortical phacoid shell. But whilst in the Phacodiscida the
phacoid shell envelops the central capsule perfectly, in the Coccodiscida
it envelops only the capsule from the two flat sides (by the upper and
lower sieve-plates); the marginal part of the lenticular capsule overgrows
the margin of the phacoid shell by peripheral extension, and fills out the
chambered cavity of the concentric girdles. In the Lithocyclida and the
Stylocyclida, where there are no chambered arms, the central capsule
remains a simple circular lens or disk; in the Astracturida, where
chambered radial arms surround the margin of the circular central disk, the
capsule enters also into these arms and fills out the greatest part of
their chambered cavities.
_Synopsis of the Genera of Coccodiscida_.
-------------------------------------------------------------------------
I. Subfamily Lithocyclida.
Margin of the disk simple, circular, without radial appendages.
-------------------------------------------------------------------------
Neither radial spines nor {Medullary shell simple, 196. _Lithocyclia_.
chambered arms on the {
circular margin. {Medullary shell double, 197. _Coccodiscus_.
-------------------------------------------------------------------------
II. Subfamily Stylocyclida.
Margin of the disk armed with solid radial spines.
-------------------------------------------------------------------------
Two opposite spines. {Medullary shell simple, 198. _Stylocyclia_.
{
{Medullary shell double, 199. _Amphicyclia_.
Three radial spines. Medullary shell simple, 200. _Trigonocyclia_.
Four crossed spines. Medullary shell simple, 201. _Staurocyclia_.
Five to ten or more {Medullary shell simple, 202. _Astrocyclia_.
radial spines. {
{Medullary shell double, 203. _Coccocyclia_.
-------------------------------------------------------------------------
III. Subfamily Astracturida.
Margin of the disk with two to five or more (commonly three or four)
hollow radial chambered arms (with or without a connecting
patagium). (Medullary shell commonly simple.)
-------------------------------------------------------------------------
Two arms, opposite in {Without patagium, 204. _Diplactura_.
one axis. {
{With patagium, 205. _Amphiactura_.
Three radial arms (at {Without patagium, 206. _Trigonactura_.
equal distances). {
{With patagium, 207. _Hymenactura_.
Four arms (in two {Without patagium, 208. _Astractura_.
crossed diameters). {
{With patagium, 209. _Stauractura_.
Five radial arms (at {Without patagium, 210. _Pentactura_.
variable distances). {
{With patagium, 211. _Echinactura_.
{459}Subfamily 1. LITHOCYCLIDA, Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with simple circular disk, without any radial
appendages of the margin (either solid radial spines or chambered arms).
Genus 196. _Lithocyclia_,[235] Ehrenberg, 1847, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 54.
_Definition._--#Coccodiscida# with simple circular margin of the disk,
without radial appendages. Medullary shell simple.
The genus _Lithocyclia_ is the most simple form of Coccodiscida, and
represents the common ancestral form of this family, from which all other
genera of it can be derived. The lenticular, biconvex disk is quite simple,
composed of a variable number of concentric, circular, chambered rings,
which are pierced by radial beams, and which surround the circular
lenticular cortical shell or "phacoid shell." The latter contains a simple
spherical medullary shell in its centre, and is connected with it by radial
beams. The margin of the disk is circular, quite simple, without radial
spines or chambered arms.
1. _Lithocyclia cingulata_, n. sp.
Phacoid shell (or lenticular porous cortical shell) three times as broad as
the spherical enclosed medullary shell, surrounded by one single chambered
girdle or ring (with about forty chambers of equal size, separated by
radial beams). Margin of the disk circular, smooth. Pores of the convex
covering plates regular, circular; eight on the radius of the phacoid
shell, two on the breadth of the ring.
_Dimensions._--Diameter of the disk (with one ring) 0.13, of the phacoid
shell 0.1, of the medullary shell 0.033.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.
2. _Lithocyclia lenticula_, n. sp. (Pl. 36, figs. 3, 4).
Phacoid shell two and a half times as broad as the enclosed medullary
shell, surrounded by three chambered girdles of equal size, which are
divided by piercing radial beams each into about fifty chambers. Margin of
the disk thorny. Pores irregular, roundish; seven on the radius of the
phacoid shell, two on the breadth of each girdle.
_Dimensions._--Diameter of the disk (with three girdles) 0.2, of the
phacoid shell 0.11, of the medullary shell 0.045.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.
{460}3. _Lithocyclia ocellus_, Ehrenberg.
_Lithocyclia ocellus_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 30;
Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxix. fig. 3.
Phacoid shell three times as broad as the medullary shell, surrounded by
numerous (seven to eleven) chambered rings, which are divided by piercing
radial beams each into sixty to ninety chambers. Margin of the disk smooth.
Pores regular, circular; nine on the radius of the phacoid shell, one
single pore on each chamber.
_Dimensions._--Diameter of the disk (with eleven rings) 0.22, of the
phacoid shell 0.1, of the medullary shell 0.035.
_Habitat._--Fossil in the rocks of Barbados.
4. _Lithocyclia monococcus_, n. sp.
_Stephanopyxis dubiosa_ (?), Bury, 1862, Polycystins of Barbados, pl.
xiii. figs. 1, 2.
Phacoid shell four times as broad as the medullary shell, surrounded by
numerous (five to eight) chambered rings, which are divided by piercing
radial beams each into fifty to seventy chambers. Margin of the disk
thickened, thorny. Pores regular, circular; seven on the radius of the
phacoid shell, one single pore on each chamber.
_Dimensions._--Diameter of the disk (with eight rings) 0.18, of the phacoid
shell 0.12, of the medullary shell 0.03.
_Habitat._--Pacific, central area, Station 267, depth 2700 fathoms; also
fossil in the rocks of Barbados.
5. _Lithocyclia heteropora_, n. sp.
Phacoid shell two and a third times as broad as the medullary shell,
surrounded by five to nine chambered rings, which are divided by piercing
radial beams each into fifty to seventy chambers. Margin of the disk
smooth. Pores very different in the inner and outer part of the surface; in
the phacoid shell larger, regular, circular, eight on its radius, in the
chambered periphery very small and irregular, somewhat spongy.
_Dimensions._--Diameter of the disk (with nine rings) 0.2, of the phacoid
shell 0.13, of the medullary shell 0.055.
_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms.
Genus 197. _Coccodiscus_,[236] Haeckel, 1862, Monogr. d. Radiol., p. 485.
_Definition._--#Coccodiscida# with simple circular margin of the disk,
without radial appendages. Medullary shell double.
The genus _Coccodiscus_ has quite the same form and structure as the
preceding _Lithocyclia_, and differs from it only in the double medullary
shell, composed of two concentric latticed spheres; sometimes the inner
medullary shell is spherical, the outer {461}lenticular; the latter is
connected with the lenticular phacoid shell (or cortical shell) by radial
beams.
1. _Coccodiscus lamarckii_, n. sp. (Pl. 36, fig. 1).
Phacoid shell (or lenticular porous cortical shell) very thick walled (as
thick as one ring), three times as broad as the outer and seven times as
broad as the inner medullary shell, surrounded by two to three chambered
rings of equal breadth, each of which is divided by piercing radial beams
into thirty-six to forty square chambers. Margin of the disk circular,
smooth. Pores regular, circular, of equal size; ten on the radius of the
phacoid shell, two on the breadth of each chamber.
_Dimensions._--Diameter of the disk (with two rings) 0.2, of the phacoid
shell 0.14, outer medullary shell 0.05, inner 0.02.
_Habitat._--Western Tropical Pacific, Station 220, depth 1100 fathoms.
2. _Coccodiscus darwinii_, Haeckel.
_Coccodiscus darwinii_, Haeckel, 1862, Monogr. d. Radiol., p. 486, Taf.
xxviii. figs. 11, 12.
Phacoid shell three times as broad as the outer and nine times as broad as
the inner medullary shell, surrounded by five to eight chambered rings of
equal breadth, each of which is divided by forty piercing radial beams into
forty square chambers of equal size. Margin of the disk smooth, circular.
Pores irregular, roundish, of unequal size; eleven on the radius of the
phacoid shell, one to two on each chamber.
_Dimensions._--Diameter of the disk (with eight rings) 0.32, of the phacoid
shell 0.11, outer medullary shell 0.036, inner 0.012.
_Habitat._--Mediterranean, Messina, surface.
3. _Coccodiscus goethei_, n. sp. (Pl. 36, fig. 2).
Phacoid shell two and a half times as broad as the outer and five times as
broad as the inner medullary shell, surrounded by three to seven chambered
rings of equal breadth, each of which is divided by piercing radial beams
into sixty to eighty chambers. Margin of the disk thorny. Pores regular,
circular; eight on the radius of the phacoid shell, a single one on the
breadth of each chamber.
_Dimensions._--Diameter of the disk (with seven rings) 0.25, of the phacoid
shell 0.1, of the medullary shell 0.04, inner 0.02.
_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.
Subfamily 2. STYLOCYCLIDA, Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with solid radial spines on the margin of the
circular disk, situated in its equatorial plane (without chambered arms).
{462}Genus 198. _Stylocyclia_,[237] Ehrenberg, 1847, Monatsber. d. k.
preuss. Akad. d. Wiss. Berlin, p. 54.
_Definition._--#Coccodiscida# with two opposite solid radial spines on the
margin of the circular disk. Medullary shell simple.
The genus _Stylocyclia_ opens the series of the Stylocyclida or of those
Coccodiscida in which the margin of the chambered disk is armed with solid
radial spines, situated in its equatorial plane, but without chambered
arms. _Stylocyclia_ is the most simple form of this subfamily, and bears
only two marginal spines, opposite in one equatorial axis of the disk. The
medullary shell is simple. This genus corresponds to _Xiphodictya_ in the
family Porodiscida. The genus was previously known only by one single
species described by Ehrenberg.
1. _Stylocyclia dimidiata_, Ehrenberg.
_Stylocyclia dimidiata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xxix. fig. 4.
Phacoid shell three times as broad as the medullary shell, surrounded by
five to eight chambered rings of equal breadth, divided by eighty to ninety
piercing radial beams into square chambers. Pores subregular, circular; six
to seven on the radius of the phacoid shell, a single one on each chamber.
Both opposite marginal spines strong, club-shaped, their thickness
decreasing from the margin towards the centre of the disk. (The figure of
Ehrenberg is very incomplete.)
_Dimensions._--Diameter of the disk (with eight rings) 0.25, of the phacoid
shell 0.11, of the medullary shell 0.035.
_Habitat._--Fossil in the Tertiary rocks of Barbados; living in the depths
of the Equatorial Atlantic, Station 348, depth (2450) fathoms.
2. _Stylocyclia prionacantha_, n. sp. (Pl. 37, fig. 6).
Phacoid shell two and a half times as broad as the medullary shell,
surrounded by five to six chambered rings, which are divided by fifty to
sixty piercing radial beams into square chambers. Pores in the thick-walled
phacoid shell regularly circular, increasing in size from the centre; eight
to nine on its radius. Pores on the surface of the chambered girdle
smaller, very irregular, two to three on each ring. Both marginal spines
longer than the diameter of the disk, with broad serrated edges.
_Dimensions._--Diameter of the disk (with five rings) 0.23, of the phacoid
shell 0.12, of the medullary 0.05.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.
{463}3. _Stylocyclia excavata_, n. sp. (Pl. 37, fig. 8).
Phacoid shell four times as broad as the medullary shell, surrounded by
four chambered rings, which are divided by twenty to thirty radial beams
into broad chambers. The height of the rings increases strongly from the
centre, so that the fourth ring is two and a half times as high as the
first. Pores irregular, roundish; five to six on the radius of the phacoid
shell, one to two on the breadth of each ring. Margin of the disk smooth.
Both marginal spines thin and long, cylindrical, arising from the medullary
shell, longer than the diameter of the disk.
_Dimensions._--Diameter of the disk (with four rings) 0.25, of the phacoid
shell 0.1, of the medullary shell 0.025.
_Habitat._--Fossil in the rocks of Barbados. Indian Ocean, Cocos Islands,
Rabbe.
4. _Stylocyclia amphacantha_, n. sp.
Phacoid shell twice as broad as the medullary shell, surrounded by five
chambered rings, divided by piercing beams each into forty to fifty
chambers. Pores regular, circular; eight to nine on the radius of the
phacoid shell, one on each chamber. Margin of the disk thorny. Both
marginal spines strong, conical, as long as its radius.
_Dimensions._--Diameter of the disk (with five rings) 0.24, of the phacoid
shell 0.1, of the medullary shell 0.05.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
Genus 199. _Amphicyclia_,[238] Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with two opposite solid radial spines on the
margin of the circular disk. Medullary shell double.
The genus _Amphicyclia_ has the same form and structure as _Stylocyclia_,
and differs from it only in the double concentric medullary shell. It bears
therefore to the latter the same relation that _Coccodiscus_ does to
_Lithocyclia_.
1. _Amphicyclia chronometra_, n. sp. (Pl. 38, fig. 1).
Phacoid shell three times as broad as the outer and nine times as broad as
the inner medullary shell, surrounded by two broad chambered rings, which
are divided into irregular chambers by fifty to sixty radial beams of
different distance. Margin of the disk thorny, lacerated. Pores irregular,
roundish; twelve to sixteen on the radius of the phacoid shell, two to
three on the breadth of each ring. The two opposite marginal spines strong,
prismatic, with prominent edges, about as long as the diameter of the disk.
_Dimensions._--Diameter of the disk (with two rings) 0.24, of the phacoid
shell 0.15, outer medullary shell 0.05, inner 0.017.
_Habitat._--Pacific, central area, Stations 265 to 268, depths 2700 to 2900
fathoms.
{464}2. _Amphicyclia amphistyla_, n. sp. (Pl. 37, fig. 7).
_Stylocyclia amphistyla_, Haeckel, 1879, MS. et Atlas (pl. xxxvii. fig.
7).
Phacoid shell thin walled, two and a half times as broad as the outer and
seven times as broad as the inner medullary shell, divided by eighty to
ninety radial beams into irregular chambers, which are stratified in four
to five floors. Pores regular, circular; eight to nine on the radius of
the phacoid shell, two on the breadth of each chamber. Both marginal
spines cylindrical.
_Dimensions._--Diameter of the disk (with seven rings) 0.27, of the phacoid
shell 0.1, outer medullary shell 0.04, inner 0.014.
_Habitat._--North Atlantic, Canary Islands, Station 354, surface.
3. _Amphicyclia pachydiscus_, n. sp. (Pl. 38, fig. 2).
Phacoid shell very thick, spongy, twice as broad as the outer and five
times as broad as the inner medullary shell, divided by fifty to seventy
radial beams into subregular chambers, which are stratified in five to six
floors. Pores irregular, roundish; ten to twelve on the radius of the
phacoid shell, two to three on the breadth of each chamber. The two
opposite marginal spines quadrangular prismatic, very long, as broad as the
radius of the inner medullary shell. Fig. 2 exhibits a vertical section
(slide) through the centre.
_Dimensions._--Diameter of the disk (with five rings) 0.22, of the phacoid
shell 0.1, outer medullary shell 0.05, inner 0.02.
_Habitat._--South Atlantic, Station 332, depth 2200 fathoms; fossil in
Barbados.
Genus 200. _Trigonocyclia_,[239] Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with three solid radial spines on the margin
of the circular disk. Medullary shell simple.
The genus _Trigonocyclia_ (only known by one single species, once observed)
bears on the margin of the chambered disk three solid radial spines, at
equal distances one from another. It corresponds to the genus
_Tripodictya_ amongst the Porodiscida.
1. _Trigonocyclia triangularis_, n. sp. (Pl. 37, fig. 5).
Phacoid shell three times as broad as the medullary shell, connected with
it by six equidistant radial beams, three of which are prolonged into
marginal spines. In the equatorial plane only one single chambered ring,
divided by forty-four radial beams into narrow chambers. Pores large,
irregular, roundish; five on the radius of the phacoid shell, two on each
chamber. Surface and margin of the disk spiny. Three strong conical
marginal spines, divergent at equal angles, as long as the radius of the
disk.
_Dimensions._--Diameter of the disk 0.16, of the phacoid shell 0.12, of the
medullary shell 0.04.
_Habitat._--Indian Ocean, Zanzibar, depth 2200 fathoms, Pullen.
{465}Genus 201. _Staurocyclia_,[240] Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with four solid radial spines on the margin
of the disk, crossed in two equatorial diameters perpendicular one to
another. Medullary shell simple.
The genus _Staurocyclia_ is characterised by four radial spines on the
margin of the disk, which are opposite in pairs and situated in two
equatorial diameters, commonly perpendicular one to another. They form
therefore a rectangular cross (rarely more or less irregular). The genus
corresponds exactly to _Staurodictya_ in the family Porodiscida. The
medullary shell is simple.
1. _Staurocyclia cruciata_, n. sp. (Pl. 37, fig. 1).
Phacoid shell two and a half times as broad as the medullary shell,
surrounded by six to eight regular rings, which are divided by fifty to
seventy piercing beams into square chambers. Pores regular, circular; six
on the radius of the phacoid shell, one single pore on each chamber. Four
crossed radial spines, arising from the medullary shell by thin bases,
prolonged over the dentated margin as four strong quadrangular swords, as
long as the radius of the disk.
_Dimensions._--Diameter of the disk (with eight rings) 0.23, of the phacoid
shell 0.09, of the medullary shell 0.035.
_Habitat_--Pacific, central area, Station 267, depth 2700 fathoms.
2. _Staurocyclia serrata_, n. sp.
? _Haliomma_ sp., Bury, 1862, Polycystins of Barbados, pl. xxii. fig. 2.
Phacoid shell twice as broad as the medullary shell, surrounded by three to
four spongy rings, which are divided by thirty to forty radial beams into
irregular chambers. Pores in the phacoid shell regular, circular, five on
its radius; in the chambered spongy girdle much smaller and irregular.
Margin dentated, with four crossed, very large, quadrangular spines, as
long as the radius of the disk, with wing-shaped, serrated edges.
_Dimensions._--Diameter of the disk (with four rings) 0.2, of the phacoid
shell 0.1, of the medullary shell 0.05.
_Habitat._--Fossil in the rocks of Barbados.
3. _Staurocyclia phacostaurus_, n. sp. (Pl. 37, figs. 2, 3).
_Phacostaurus pyramidalis_, Haeckel, 1879, MS. (as a separate genus).
Phacoid shell two and a quarter times as broad as the medullary shell,
connected with it by twelve radial beams (four equatorial and eight
divergent) and surrounded by one single ring, which is divided by forty
radial beams into regular chambers. Pores regular, honeycomb-like in the
{466}phacoid shell, seven on its radius; smaller on the equatorial ring,
three on its breadth. Four marginal spines pyramidal four-sided, as long
and as broad at the base as the ring.
_Dimensions._--Diameter of the disk (with one ring) 0.14, of the phacoid
shell 0.11, of the medullary shell 0.048.
_Habitat._--South Atlantic, Station 335, depth 1425 fathoms.
4. _Staurocyclia magniducis_, n. sp. (Pl. 37, fig. 4).
_Coccostaurus magniducis_, Haeckel, 1881, MS. et Atlas (pl. xxxvii. fig.
4).
Phacoid shell twice as broad as the medullary shell, connected with it by
numerous radial beams and surrounded by eight chambered rings, which are
divided by one hundred to one hundred and twenty piercing radial beams into
small chambers. Pores subregular, circular; ten on the radius of the
phacoid shell, two on the breadth of each chamber. Margin of the disk armed
with numerous bristle-shaped radial spines, as long as the breadth of the
chambered girdle. Four very large crossed spines, nearly as long as the
diameter of the disk, quadrangular, with four dentated edges; at the
club-shaped distal end thorny, as broad as the medullary shell and three
times as broad as at the narrow base. I name this splendid species in the
honour of H.R.H. the Grand Duke of Saxe-Weimar, Carl Alexander, the
magnanimous protector of arts and sciences, the rector magnificentissimus
of the University of Jena.
_Dimensions._--Diameter of the disk (with eight rings) 0.27, of the phacoid
shell 0.11, of the medullary shell 0.05; length of the four crossed
club-spines 0.2, basal breadth 0.02, distal breadth 0.06.
_Habitat._--Indian Ocean, Ceylon, Belligemma, surface (Haeckel).
Genus 202. _Astrocyclia_,[241] Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with numerous (five or more, commonly thirty
to sixty) solid radial spines on the margin of the circular disk. Medullary
shell simple.
The genus _Astrocyclia_ exhibits on the margin of the circular chambered
disk a large but variable number of solid radial spines, commonly between
thirty and sixty. They are the external prolongations of the inner piercing
radial beams, which divide the concentric rings of the disk into chambers.
All the spines lie in the equatorial plane of the disk. The genus
corresponds to _Stylodictya_ in the family Porodiscida.
1. _Astrocyclia solaster_, n. sp. (Pl. 36, fig. 7).
Phacoid shell two and a half times as broad as the medullary shell,
surrounded by four to six regular rings of equal breadth, which are divided
by thirty to forty piercing radial beams into broad {467}chambers. Pores
regular, circular; seven on the radius of the phacoid shell, one single
pore on each chamber (the size increasing from the centre). Margin with
thirty to forty angular, broad, dentate spines, the prolongations of the
inner radial beams.
_Dimensions._--Diameter of the disk (with six rings) 0.22, of the phacoid
shell 0.1, of the medullary shell 0.04.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.
2. _Astrocyclia stella_, Haeckel.
_Lithocyclia stella_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 78, Taf. xxix. fig. 2.
Phacoid shell three times as broad as the medullary shell, surrounded by
four to eight rings of increasing breadth from the centre, the outer of
which are more or less spongy. Each ring is divided by forty to fifty
piercing radial beams into chambers of increasing size. Pores regular,
circular; a single one on each chamber, ten on the radius of the phacoid
shell. On the margin are scattered ten to twenty thick and short spines,
four-sided pyramidal, about as long and as broad at the base as the
diameter of the medullary shell.
_Dimensions._--Diameter of the disk (with eight rings) 0.25, of the phacoid
shell 0.09, of the medullary shell 0.03.
_Habitat._--Fossil in the rocks of Barbados.
3. _Astrocyclia rotula_, n. sp.
Phacoid shell four times as broad as the medullary shell, surrounded by one
single ring, which is divided by forty radial beams into equal chambers.
Pores regular, circular; two on the breadth of the ring, six on the radius
of the phacoid shell. Margin with forty short, conical spines, the
prolongations of the inner radial beams, twice as long as the breadth of
the ring.
_Dimensions._--Diameter of the disk 0.13, of the phacoid shell 0.1, of the
medullary shell 0.025.
_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.
4. _Astrocyclia arachnia_, n. sp.
Phacoid shell twice as broad as the medullary shell, surrounded by four to
six rings of equal breadth, which are divided by twelve to twenty radial
beams into broad chambers. Pores regular, circular; two on the breadth of
each ring, eight on the radius of the phacoid shell. Margin with twelve to
twenty very long and thin, bristle-shaped, radial spines, the prolongations
of the inner beams, longer than the diameter of the disk. (Resembles
_Stylodictya arachnia_, but differs in the possession of a phacoid shell.)
_Dimensions._--Diameter of the disk (with six rings) 0.22, of the phacoid
shell 0.09, of the medullary shell 0.045.
_Habitat._--North Atlantic, Canary Islands.
{468}5. _Astrocyclia heterocycla_, n. sp. (Pl. 36, fig. 8). Phacoid shell
two and a half times as broad as the medullary shell, surrounded by three
rings of unequal breadth, the first ring as broad as the second and third
together. They are divided by fifty to sixty piercing radial beams into
chambers, which are square in the second and third rings, and half as large
as in the first. The radial beams are alternately thicker and thinner,
prolonged into short marginal spines. Pores subregular, circular; eight on
the radius of the phacoid shell, two on the breadth of the first ring, a
single one on each chamber of the second and third rings.
_Dimensions._--Diameter of the disk (with three rings) 0.2, of the phacoid
shell 0.12, of the medullary shell 0.05.
_Habitat._--Equatorial Atlantic, Station 348, depth (2450) fathoms; also
fossil in Barbados.
Genus 203. _Coccocyclia_,[242] Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with numerous (five or more) solid radial
spines on the margin of the circular disk. Medullary shell double.
The genus _Coccocyclia_ has the same form and structure as the foregoing
_Astrocyclia_, and differs from it only in the double concentric medullary
shell. It bears therefore to the latter the same relation as _Coccodiscus_
to _Lithocyclia_.
1. _Coccocyclia liriantha_, n. sp.
Phacoid shell three times as broad as the outer and ten times as broad as
the inner medullary shell, connected with both by six equidistant piercing
radial beams. The margin of the phacoid shell is surrounded by one or two
equatorial rings, each as broad as the outer medullary shell, and divided
by thirty to forty radial beams into narrow chambers. Pores subregular,
circular, about nine to ten on the radius of the phacoid shell, three to
four on the breadth of each ring. Margin of the disk ciliated, with six
regularly disposed radial spines as prolongations of the inner six piercing
beams. Each spine cylindrical, delicately crenulated, about as broad as the
inner medullary shell, and once to twice as long as the diameter of the
whole disk, elegantly undulated, with a conical terminal point.
_Dimensions._--Diameter of the disk (with two rings) 0.32, of the phacoid
shell 0.2, of the outer medullary shell 0.06, of the inner 0.02.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
2. _Coccocyclia heliantha_, n. sp. (Pl. 36, figs. 5, 6).
Phacoid shell two and a half times as broad as the outer and six times as
broad as the inner medullary shell, surrounded by six to eight rings of
nearly equal breadth, the outer somewhat smaller. They are divided by fifty
to sixty piercing radial beams into irregular chambers. Pores
{469}irregular, roundish; ten on the radius of the phacoid shell, a single
one on each chamber of the equatorial girdle. Margin of the disk with
numerous strong conical radial spines of different breadths, arranged in
several circles, the strongest in the equatorial plane, about as broad as
one ring and twice as long. Surface thorny.
_Dimensions._--Diameter of the disk (with seven rings) 0.3, of the phacoid
shell 0.12, of the outer medullary shell 0.05, of the inner 0.02.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; also
fossil in Barbados.
Subfamily 3. ASTRACTURIDA, Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with two or more (commonly three or four)
chambered radial arms on the margin of the disk, situated in its equatorial
plane (with or without a connecting patagium between the arms).
Genus 204. _Diplactura_,[243] Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with two opposite chambered arms on the
margin of the circular disk, without a connecting patagium.
The genus _Diplactura_ is the simplest form of the Astracturida, or of
those Coccodiscida in which the margin of the disk bears chambered arms,
situated in its equatorial plane. This subfamily corresponds to the
Euchitonida among the Porodiscida, to the Spongobrachida among the
Spongodiscida. In _Diplactura_ there are only two free arms, opposite in
one equatorial diameter (corresponding to _Amphibrachium_ among the former,
to _Spongolena_ among the latter).
Subgenus 1. _Diplacturium_, Haeckel.
_Definition._--Arms blunt at the distal end, without radial spines.
1. _Diplactura diplobrachia_, n. sp.
Phacoid shell twice as broad as the medullary shell, with six pores on its
radius, without a perfect chambered ring around it. Arms club-shaped, one
and a half times as long as the diameter of the phacoid shell, at the
distal end rounded, blunt, as broad as the latter, at the base only half as
broad.
_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell
0.04; length of the arms 0.12, basal breadth 0.04, distal breadth 0.08.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
{470}Subgenus 2. _Diplactinium_, Haeckel.
_Definition._--Arms on the distal end armed with a radial terminal spine.
2. _Diplactura diploconus_, n. sp. (Pl. 38, fig. 5).
_Amphiactura diploconus_, Haeckel, 1877, MS. et Atlas (pl. xxxviii. fig.
5).
Phacoid shell three times as broad as the medullary shell, with eight pores
on its radius, surrounded by a single chambered ring. Arms club-shaped,
twice as long as the diameter of the phacoid shell, at the distal end as
broad as the latter, at the base only half as broad. Both poles of the
common axis of the arms are armed with a strong spindle-shaped terminal
spine.
_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell
0.03; length of the arms (without terminal spines) 0.17, basal breadth
0.05, distal breadth 0.09.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.
Genus 205. _Amphiactura_,[244] Haeckel, 1881, Prodromus, p. 458.
_Definition._--#Coccodiscida# with two opposite chambered arms on the
margin of the circular disk, connected by a spongy patagium.
The genus _Amphiactura_ differs from the foregoing _Diplactura_ in the
development of a patagium between the arms, and therefore bears the same
relation to it as _Amphymenium_ in the Porodiscida does to _Amphibrachium_,
or _Spongobrachium_ in the Spongodiscida does to _Spongolene_. In this and
in the following #Discoidea# provided with a patagium, this connecting web
constantly exhibits a different texture of its framework, which is
sometimes more regularly chambered, at other times more irregularly spongy.
1. _Amphiactura amphibrachia_, n. sp. (Pl. 38, figs. 3, 4).
Phacoid shell three times as broad as the medullary shell, with eight pores
on its radius. Arms nearly equilateral triangular, twice as long as the
diameter of the phacoid shell, at the truncated distal end as broad as the
latter, at the base only one-third as broad. Patagium a circular lenticular
disk, enveloping only the basal third of the arms, with three to four
concentric circular rings, divided into chambers by about forty radial
beams, which are prolonged beyond the margin of the patagium into radial
spines. The vertical section (fig. 4) shows that the chambers of each arm
(eleven to twelve transverse rows in the radius) are disposed in two
layers.
_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell
0.03; length of the arms 0.18, basal breadth 0.03, distal breadth 0.09.
_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms.
{471}Genus 206. _Trigonactura_,[245] Haeckel, 1881, Prodromus, p. 459.
_Definition._--#Coccodiscida# with three chambered arms on the margin of
the circular or triangular disk, without a connecting patagium.
The genus _Trigonactura_ exhibits three radial arms, which in all known
species are separated by three equal angles. The terminal points of the
arm-axes are the corners of an equilateral triangle. It corresponds
therefore to _Dictyastrum_ among the Porodiscida.
Subgenus 1. _Trigonacturium_, Haeckel.
_Definition._--Distal end of the arms blunt or truncated, without a
terminal spine.
1. _Trigonactura pythagoræ_, Haeckel.
_Astromma pythagoræ_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 66, Taf. xxx. fig. 2.
Phacoid shell circular, twice as broad as the medullary shell, with five
pores on its radius, without a completely surrounding chambered girdle.
Arms nearly square, at the truncated distal end as broad as long, and
scarcely broader than at the base, two-thirds as long as the diameter of
the central disk.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.05; length of the arms 0.07, distal breadth 0.07.
_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, in various depths;
also fossil in Tertiary rocks of Barbados and Nicobar.
2. _Trigonactura rhopalastrella_, n. sp.
_Stephanastrum_ sp., Bury, 1862, Polycystins of Barbados, pl. xv. fig. 7.
Phacoid shell twice as broad as the medullary shell, with five pores on its
radius, without a perfect chambered ring around it. Arms club-shaped, at
the blunt distal end rounded, as long as the diameter of the phacoid shell;
their basal breadth is one-fourth, their distal breadth one-half of its
length.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.05; length of the arms 0.1, basal breadth 0.025, distal breadth 0.05.
_Habitat._--Pacific, central area, Stations 270 to 274, depths 2400 to 2800
fathoms; also fossil in Tertiary rocks of Barbados.
{472}3. _Trigonactura trigonobrachia_, n. sp.
Phacoid shell two and a half times as broad as the medullary shell, with
six pores on its radius, without a perfect chambered girdle. Arms nearly
equilateral triangular, twice as long as the diameter of the phacoid shell,
at the truncated distal end as broad as its diameter and three times as
broad as at the narrow base. (Resembles _Hymenactura hexagona_, but without
a patagium.)
_Dimensions._--Diameter of the phacoid shell 0.11, of the medullary shell
0.045; length of the arms 0.2, basal breadth 0.035, distal breadth 0.1.
_Habitat._--North Pacific, Station 244, depth 2900 fathoms.
4. _Trigonactura lanceolata_, n. sp.
Phacoid shell three times as broad as the medullary shell, with eight pores
on its radius, surrounded by one perfect chambered ring. Arms lanceolate,
three times as long as the diameter of the phacoid shell, and four times as
long as broad in the middle part, at both ends very narrow, blunt.
_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell
0.03; length of the arms 0.25, breadth in the midst 0.06.
_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.
Subgenus 2. _Trigonactinium_, Haeckel.
_Definition._--Distal end of the arms armed with a radial spine.
5. _Trigonactura triacantha_, n. sp. (Pl. 38, figs. 6, 7).
Phacoid shell two and a half times as broad as the medullary shell, with
eight pores on its radius, surrounded by one perfect chambered ring. Arms
nearly lanceolate, in the middle part one and a half times as broad as at
both ends, twice as long as the phacoid shell, at the distal end with a
strong pyramidal terminal spine. Through the spongy framework of each arm
shine sixteen to eighteen transverse bars (as septa of the joints) and six
to eight longitudinal piercing beams.
_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell
0.038; length of the arms 0.2, greatest breadth 0.08.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
6. _Trigonactura trigonodiscus_, n. sp.
? _Astromma_ sp., Bury, 1862, Polycystins of Barbados, Taf. xv. fig. 2.
Phacoid shell triangular, twice as broad as the spherical medullary shell,
with six to seven pores on its radius, surrounded by one chambered ring.
Arms equilateral triangular, as long as {473}the diameter of the central
disk and at the base half as broad, slowly decreasing in breadth towards
the distal end, which is armed with a strong pyramidal spine.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.05; length of the arms 0.12, basal breadth 0.07.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; also
fossil in Barbados.
7. _Trigonactura trixiphos_, n. sp.
Phacoid shell circular, twice as broad as the medullary shell, without a
completely surrounding chambered ring, with four pores on its radius. Arms
club-shaped, about as long as the diameter of the central disk, at the base
half as broad as long, at the rounded distal end broader, and armed with a
strong pyramidal terminal spine, nearly as long as the arm itself.
_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell
0.04; length of the arms (without terminal spine) 0.08, basal breadth 0.04,
distal breadth 0.06.
_Habitat._--Fossil in the rocks of Barbados.
Genus 207. _Hymenactura_,[246] Haeckel, 1881, Prodromus, p. 459.
_Definition._--#Coccodiscida# with three chambered arms on the margin of
the circular or triangular disk, connected by a spongy patagium.
The genus _Hymenactura_ differs from the foregoing _Trigonactura_ in the
spongy patagium between the arms, and bears therefore to it the same
relation that among the Porodiscida _Hymeniastrum_ does to the simpler
_Dictyastrum_. The oldest known species of this genus is _Hymenactura
pythagoræ_, described by Ehrenberg as _Hymeniastrum pythagoræ_, but
differing from this in the structure of the central disk.
Subgenus 1. _Hymenacturium_, Haeckel.
_Definition._--Distal end of the arms blunt or truncated, without terminal
spines.
1. _Hymenactura archimedis_, n. sp. (Pl. 38, fig. 8).
Phacoid shell three times as broad as the medullary shell, with eight pores
on its radius. Arms nearly trapezoidal, somewhat longer than the diameter
of the central disk, at the truncated distal end nearly as broad, at the
base only half as broad. In each arm eleven to twelve transverse rows of
square chambers, each of which exhibits on the surface one large pore.
Patagium enveloping the basal half of the arms, with four to five convex
rows of chambers, forming together a circular concentric disk.
_Dimensions._--Diameter of the phacoid shell 0.11, of the medullary shell
0.035; length of the arms 0.12, basal breadth 0.05, distal breadth 0.1.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.
{474}2. _Hymenactura pythagoræ_, Haeckel.
_Hymeniastrum pythagoræ_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig.
31; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 76, Taf. xxx. fig. 5.
Phacoid shell three times as broad as the medullary shell, with six pores
on its radius. Arms nearly trapezoidal, somewhat longer than the diameter
of the central disk, at the truncated distal end nearly as broad, at the
base two-thirds as broad. In each arm eight to nine transverse rows of
square chambers, each chamber with one pore on the surface. Patagium
enveloping the basal half of the arms, with four to five rectilinear
parallel rows of chambers, forming together a regular triangle. Differs
from the preceding species mainly in the quite different structure of the
patagium, from the true _Hymeniastrum pythagoræ_ in the phacoid shell of
the central disk, which encloses only one simple medullary shell.
_Dimensions._--Diameter of the phacoid shell 0.11, of the medullary shell
0.04; length of the arms 0.13, basal breadth 0.07, distal breadth 0.12.
_Habitat._--Fossil in the rocks of Barbados.
3. _Hymenactura trigona_, n. sp.
_Astromma_ sp., Bury, 1862, Polycystins of Barbados, pl. xv. fig. 1.
Phacoid shell twice as broad as the medullary shell, with four to five
pores on its radius. Arms slender, lanceolate, three times as long as the
diameter of the phacoid shell and five times as long as broad in the middle
part; distal ends blunt. Patagium enveloping only the basal half of the
arms, forming a regular triangle with concave sides.
_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell
0.035; length of the arms 0.2, greatest breadth 0.04.
_Habitat._--South Atlantic, Station 332, depth 2200 fathoms; fossil in the
rocks of Barbados.
4. _Hymenactura hexagona_.
_Hymeniastrum_ sp., Bury, 1862, Polycystins of Barbados, pl. xv. fig. 3.
Phacoid shell twice as broad as the medullary shell, with four to five
pores on its radius. Arms nearly equilateral triangular, three times as
long as the diameter of the phacoid shell, at the truncated distal end
nearly three-fourths as broad as long, at the narrow base only one-fourth
as broad. Patagium complete, enveloping the arms completely, so that the
whole body represents a regular hexagonal disk.
_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell
0.04; length of the arms 0.18, basal breadth 0.04, distal breadth 0.16.
_Habitat._--Fossil in the rocks of Barbados and Nicobar.
{475}Subgenus 2. _Hymenactinium_, Haeckel.
_Definition._--Distal ends of the arms armed with terminal spines.
5. _Hymenactura ptolemæi_, n. sp.
_Astromma_ sp., Bury, 1862, Polycystins of Barbados, pl. xv. figs. 5, 6.
Phacoid shell twice as broad as the medullary shell, with six to seven
pores on its radius. Arms nearly square, about as large as the phacoid
shell, at the truncated distal end little broader than at the base, and
armed with a strong pyramidal terminal spine. Patagium incomplete,
enveloping the basal half of the arms.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.05; length and greatest breadth of the arms 0.08.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; fossil
in the rocks of Barbados.
6. _Hymenactura copernici_, n. sp. (Pl. 38, fig. 9).
Phacoid shell three times as broad as the medullary shell, with six pores
on its radius. Arms lanceolate, nearly twice as long as the phacoid shell,
in the middle part twice as broad as the medullary shell, with a strong
conical terminal spine at the distal end. In each arm about ten transverse
rows of chambers. Patagium enveloping the basal half of the arms, with four
convex parallel rows of chambers.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.035; length of the arms 0.17, greatest breadth 0.07.
_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms.
Genus 208. _Astractura_,[247] Haeckel, 1881, Prodromus, p. 459.
_Definition._--#Coccodiscida# with four chambered arms on the margin of the
circular or quadrangular disk, crossed in two equatorial diameters, without
a connecting patagium.
The genus _Astractura_ has the form of a regular cross, four radial arms
being opposite in two equatorial diameters perpendicular one to another. In
the Porodiscida the same form is repeated by _Stauralastrum_, in the
Spongodiscida by _Spongasteriscus_. The oldest known species of the genus
is _Astromma aristotelis_ of Ehrenberg, in which genus this author
confounded triradial and four-radial forms.
{476}Subgenus 1. _Astracturium_, Haeckel.
_Definition._--Distal end of the arms blunt or truncated, without terminal
spines.
1. _Astractura ordinata_, n. sp.
? _Astromma_ sp., Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 3.
Phacoid shell three times as broad as the medullary shell, with six pores
on its radius, without a completely developed chambered ring. Arms
trapezoidal, somewhat longer than the radius of the disk, at the truncated
distal end as broad as long, at the base one-third smaller.
_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell
0.03; length of the arms 0.05, distal breadth 0.05, basal breadth 0.035.
_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms; also fossil
in Barbados.
2. _Astractura clavigera_, n. sp.
_Astromma aristotelis_, Bury, 1862, Polycystins of Barbados, pl. iv. fig.
2.
Phacoid shell twice as broad as the medullary shell, with ten pores on its
radius, surrounded by one perfect chambered ring. Arms club-shaped, about
as long as the radius of the central disk, at the rounded distal end
two-thirds, at the base one-third as broad as long.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.05; length of the arms 0.06, basal breadth 0.02, distal breadth 0.04.
_Habitat._--Pacific, central area, Stations 270 to 274, depths 2350 to 2925
fathoms; fossil in the rocks of Barbados.
Subgenus 2. _Astractinium_, Haeckel.
_Definition._--Distal end of the arms furnished with a radial spine.
3. _Astractura aristotelis_, Haeckel.
_Astromma aristotelis_, Ehrenberg, 1856, Microgeol., Taf. xxxvi. fig. 32;
Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 66, Taf. xxx. fig. 4.
_Astromma aristotelis_, Haeckel, 1862, Monogr. d. Radiol., p. 489.
? _Astromma aristotelis_, Bury, 1862, Polycystins of Barbados, pl. xiv.
fig. 4.
Phacoid shell three times as broad as the medullary shell, with six to
eight pores on its radius, surrounded by one perfect chambered ring. Arms
nearly trapezoidal, about as long as the diameter of the central disk, at
the base half as broad, at the truncated distal end nearly as broad as
long, and armed with a large pyramidal terminal spine. Each arm with about
eight transverse and longitudinal rows of chambers.
{477}_Dimensions._--Diameter of the phacoid shell 0.11, of the medullary
shell 0.04; length of the arms 0.1, basal breadth 0.05, distal breadth
0.09.
_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, at various depths;
fossil in the Tertiary rocks of Barbados and Nicobar.
4. _Astractura democriti_, n. sp.
_Astromma aristotelis_, var., Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 66, Taf, xxx. fig. 3.
? _Astromma aristotelis_, var., Bury, 1862, Polycystins of Barbados, pl.
xiv. fig. 4.
Phacoid shell twice as broad as the medullary shell, with five to seven
pores on its radius, without perfect chambered ring. Arms about twice as
long as broad, longer than the diameter of the central disk, at the
truncated distal end a little broader than at the base, and armed with a
strong, pyramidal, terminal spine.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.05; length of the arms 0.15, basal breadth 0.04, distal breadth 0.08.
_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms; fossil
in Barbados.
5. _Astractura hippocratis_, n. sp.
Phacoid shell three times as broad as the medullary shell, with seven pores
on its radius, surrounded by two to three perfect chambered rings. Arms
nearly square, scarcely as long and nearly as broad as the diameter of the
central disk, at the rounded distal end armed with a very strong,
pyramidal, terminal spine, longer than the arm itself, and at the base as
broad as the medullary shell.
_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell
0.03; length of the arms 0.08, breadth 0.1.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
Genus 209. _Stauractura_,[248] Haeckel, 1881, Prodromus, p. 459.
_Definition._--#Coccodiscida# with four chambered arms on the margin of the
circular or quadrangular disk, crossed in two equatorial diameters,
connected by a spongy patagium.
The genus _Stauractura_ differs from the foregoing in the patagium between
the arms, and bears therefore the same relation to it as _Histiastrum_ in
the Porodiscida does to _Stauralastrum_. All known species of this genus
form a regular square, if we connect the end points of the arm axes by
lines.
Subgenus 1. _Stauracturium_, Haeckel.
_Definition._--Distal end of the arms blunt or truncated, without terminal
spines.
{478}1. _Stauractura octogona_, n. sp.
Phacoid shell twice as broad as the medullary shell, with eight pores in
its radius. Arms nearly square, little larger than the phacoid shell, with
broad truncated distal ends. The corners of the latter are so connected by
the complete patagium, that the whole shell forms a regular octagon.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.05; length of the arms 0.12, distal breadth 0.11.
_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms.
2. _Stauractura tetragona_, n. sp.
Phacoid shell three times as broad as the medullary shell, with eleven
pores on its radius. Arms club-shaped, nearly as long as the diameter of
the phacoid shell, and one and a half times as long as broad at the distal
part; at the distal end rounded, blunt, without terminal spine. The
terminal points of the arms are so connected by a thin, complete patagium,
that the whole shell becomes a regular square.
_Dimensions._--Diameter of the phacoid shell 0.13, of the medullary shell
0.045; length of the arms 0.12, greatest breadth 0.08.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
Subgenus 2. _Stauractinium_, Haeckel.
_Definition._--Distal end of the arms furnished with a radial spine.
3. _Stauractura medusina_, n. sp.
Phacoid shell two and a half times as broad as the medullary shell, with
nine pores on its radius. Arms club-shaped, one and a half times as long as
the diameter of the phacoid shell, and in the outer third nearly as broad
as the latter, at the base scarcely one-third as broad; their truncated
distal end armed with a strong pyramidal terminal spine. Patagium
incomplete, enveloping only the basal half of the arms, with three
rectilinear parallel rows of chambers, forming a square.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.04; length of the arms 0.14, greatest breadth 0.08.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.
4. _Stauractura quadrata_, n. sp.
Phacoid shell twice as broad as the medullary shell, with seven pores on
the radius. Arms nearly square, about as large as the phacoid shell, with a
strong pyramidal terminal spine at the distal end. Patagium complete,
between every two arms triangular, with rectilinear parallel {479}rows of
chambers; it connects the end points of the arm radius in such a manner
that the whole shell becomes a regular square.
_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell
0.045; length of the arms 0.1, greatest breadth 0.08.
_Habitat._--South Pacific, Station 295, depth 1500 fathoms.
Genus 210. _Pentactura_,[249] Haeckel, 1881, Prodromus, p. 459.
_Definition._--#Coccodiscida# with five chambered arms on the margin of the
circular or pentagonal disk, without a connecting patagium.
The genus _Pentactura_ possesses five free radial arms, and resembles
_Pentalastrum_ among the Porodiscida. The distance of the five arms seems
to be sometimes equal, at other times different in one and the same
species.
1. _Pentactura pentactis_, Haeckel.
_Astromma pentactis_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 66, Taf. xxx. fig. 1.
Phacoid shell two and a half times as broad as the medullary shell, with
eight pores on its radius. Arms regularly or irregularly disposed, nearly
square, about half as large as the phacoid shell, at the truncated distal
end little broader than at the base. In the specimen figured, and very
imperfectly described by Ehrenberg, (_loc. cit._), the arms were
asymmetrically disposed, two opposite in one axis of the disk, two others
on one side of this axis, the fifth opposite to these on the other side.
Another specimen which I found in the Barbados rocks had five arms of equal
size, regularly disposed, at equal intervals.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.04; length and breadth of the arms 0.05 to 0.06.
_Habitat._--Fossil in the rocks of Barbados.
2. _Pentactura astropecten_, n. sp.
Phacoid shell three times as broad as the medullary shell, with ten pores
on its radius. Arms regularly disposed, club-shaped, nearly twice as long
as the diameter of the phacoid shell, and equal to it in breadth at the
rounded distal end. The latter is armed with a short conical spine, and is
twice as broad as the base.
_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell
0.03; length of the arms 0.17, basal breadth 0.05, distal breadth 0.08.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
{480}Genus 211. _Echinactura_,[250] n. gen.
_Definition._--#Coccodiscida# with five chambered arms on the margin of the
circular or pentagonal disk, connected by a spongy patagium.
The genus _Echinactura_ differs from the foregoing _Pentactura_ in the
patagium between the arms, and bears therefore the same relation to it as
_Pentinastrum_ in the Porodiscida does to _Pentalastrum_.
1. _Echinactura culcita_, n. sp.
Phacoid shell pentagonal, three times as broad as the medullary shell, with
nine pores on its radius. Arms egg-shaped, about as long as the diameter of
the phacoid shell, and in the distal part half as broad. The blunt ends of
the arms are so connected by the complete patagium that the whole shell
becomes a regular pentagonal disk.
_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell
0.035; length of the arms 0.11, basal breadth 0.04, distal breadth 0.06.
_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms.
2. _Echinactura asteriscus_, n. sp.
Phacoid shell twice as broad as the medullary shell, with seven pores on
its radius. Arms lanceolate, twice as long as the diameter of the phacoid
shell, in the middle part nearly as broad as the latter, at the distal end
with a strong conical terminal spine. Patagium incomplete, enveloping only
the basal half of the arms.
_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell
0.045; length of the arms 0.2, greatest breadth 0.08.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.
3. _Echinactura goniaster_, n. sp.
Phacoid shell three times as broad as the medullary shell, with nine pores
on its radius. Arms club-shaped, one and a half times as long as the
diameter of the phacoid shell, in the distal part nearly as broad as the
latter, in the basal part one-third as broad; at the end a strong pyramidal
spine. Patagium nearly complete, with concave dentated margin between each
pair of arms, therefore the pentagonal disk of the whole shell with concave
sides.
_Dimensions._--Diameter of the phacoid shell 0.12, of the medullary shell
0.04; length of the arms (without terminal spine) 0.18, basal breadth 0.04,
distal breadth 0.1.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
{481}Family XXI. #PORODISCIDA#, Haeckel (Pls. 41-47).
_Porodiscida_, Haeckel, 1881, Prodromus, p. 459.
_Trematodiscida_ et _Discospirida_, Haeckel, 1862, Monogr. d. Radiol.,
pp. 485, 491, 513.
_Calodictya_, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss.
Berlin, p. 53 (_partim_).
_Definition._--#Discoidea# without phacoid shell, with flat discoidal
shell, in which a simple spherical central chamber is surrounded by
concentric chambered rings (each ring divided by radial beams into
imperfect chambers). Surface of the disk on the two flat sides covered by
a porous sieve-plate.
The family #Porodiscida# is by far the largest and richest in different and
common forms among all #Discoidea#; already in my Monograph (1862) nine
genera and twenty-eight species have been enumerated. Their number is here
increased to more than thirty genera and two hundred species. Many of these
species appertain to the most common and widely distributed SPUMELLARIA,
both living and fossil. But the study of their structure is not easy, and
requires (as in the foregoing Coccodiscida) not only careful examination of
the facial views of the disk, but also of the marginal view and of slides
and sections through different planes.
In my Monograph (1862, pp. 485, 491, 513) I had constituted for these
#Discoidea# two different families, the Trematodiscida and Discospirida;
but the comparative study of a far greater number of different types in the
Challenger collection has since convinced me that those two families are
but little different, and united by transitional forms within one and the
same genus, so that they must be united as Porodiscida. Of the group, which
Ehrenberg formerly had called "Calodictya," many genera appertain to the
Porodiscida, whilst many others are true Spongodiscida.
The Porodiscida represent the first and the most important family of the
#Cyclodiscaria#, or of those #Discoidea# which are devoid of the peculiar
extracapsular lenticular "phacoid shell," characteristic of the three
preceding families (united therefore as #Phacodiscaria#). Probably all
#Cyclodiscaria# can be derived from _Archidiscus_, from a morphological as
well as a phylogenetic point of view. _Archidiscus_ seems to be the common
ancestral form not only of the Porodiscida, but also of the nearly allied
Pylodiscida and Spongodiscida. This important _Archidiscus_ (Pl. 48, figs.
9-11) is a small lenticular circular disk, in which a simple latticed
spherical central chamber is surrounded by one single concentric ring,
connected with it by a variable number of radial beams in the equatorial
plane. From this typical _Archidiscus_, as from their "architype," all
other #Cyclodiscaria# may be derived; the Porodiscida by regular apposition
of new concentric chambered rings on the margin, the Spongodiscida by
irregular apposition of a spongy framework, the Pylodiscida by a peculiar
interrupted, concentric, triradial growth, three radial arm-chambers
alternating with three open gates or holes, so that already the first
chambered ring is not complete.
{482}_Archidiscus_ (Pl. 48, figs. 9-11) is not only the common phylogenetic
ancestral form of all #Cyclodiscaria#, but also the common ontogenetic
original form of all Porodiscida, or at least of the greater part of them.
The numerous species of _Archidiscus_, which are distinguished in the
sequel, are at the same time the embryonic forms of different Porodiscida,
corresponding to the "biogenetic main law of development." The small shell
of _Archidiscus_ is sometimes completely lenticular, circular, at other
times more or less polygonal; commonly on the biconvex centre much thicker
than on the margin, but sometimes also of nearly equal thickness (like a
medal or a short cylinder). The latticed central chamber of it is probably
in the majority of species spherical, but in some more or less compressed,
lenticular; the number of small pores on its surface is probably commonly
between ten and twenty (four to eight usually being visible on each
hemisphere). The number of radial beams, which connect it with the
equatorial ring, varies commonly from four to eight; but sometimes only two
or three are to be found, in other cases nine to ten or more. The regular
disposition of these beams (in certain equatorial axes of the disk) is
probably of great importance, as determining the later development of
characteristic radial appendages of the margin in the more highly developed
Porodiscida. The equatorial ring itself, forming the margin of the
lenticular disk, is either a simple solid ring or a broader latticed
girdle; in the latter case it merges slowly into the opposite sieve-plates
of the two flat disk sides, or the porous "cover-plates," covering its
parallel or convex surfaces. These latter can be regarded as direct
peripheral continuations of the polar regions of the spherical central
chamber. The ring-chambers, surrounding the latter in a single circle, are
commonly of nearly the same breadth, but often also of different irregular
size. Their number varies between two and ten or more, but commonly between
four and eight; each ring-chamber is covered on the upper and lower side by
the sieve-plate, bounded on the inner (proximal) side by the wall of the
central chamber, on the outer (distal) side by the marginal ring, on both
lateral sides by the contiguous neighbouring ring-chambers.
The important question as to the phylogenetic origin of _Archidiscus_ can
be answered in a twofold way. The most simple form of _Archidiscus_
(_Archidiscus dioniscus_) can be derived immediately from the
Stylosphærida, _Saturnalis_ (Pl. 13, fig. 16), only by the development of
lattice-work between the equatorial ring and the two polar faces of the
concentric central chamber (on the surface of the biconvex jelly-mantle).
But on the other hand _Archidiscus_ may also be derived from the simplest
Phacodiscida, _Sethodiscus_ (Pl. 33, figs. 1-3), by the stronger
compression of the biconvex lenticular shell, so that the enclosed
medullary shell on the two poles runs together with the lenticular phacoid
shell, of which only the peripheral part remains free, and thus forms the
chambered ring; this latter explanation seems the more natural in many
cases, as often in the Porodiscida the central chamber is enclosed in one
or two concentric spherical or lenticular lattice-shells.
{483}The second subfamily of the Porodiscida are the Trematodiscida, which
are derived from the preceding Archidiscida by concentric growth in the
equatorial plane. In the same way in which the simple chambered ring of
_Archidiscus_ is connected by radial beams with the central chamber, so in
_Porodiscus_ a variable number of concentric rings is connected with that
first ring. The number of these concentric rings varies between two and ten
or more, but commonly amounts to between three and five. The radial beams
connecting them are either piercing or interrupted; their number increases
gradually from the centre towards the periphery. The chambers between them
are sometimes more regular, at other times more irregular in size and form.
Their upper and lower wall is formed by the two covering "sieve-plates,"
or the porous cover-plates, which are continued from the central disk to
the margin. If these two sieve-plates continue being parallel, the disk
becomes medal-shaped or a short cylinder; if the two plates become more or
less concavely vaulted one against the other, the disk becomes biconvex
lenticular, the middle part thicker than the marginal part. Rarely the
contrary is the case, the margin thicker than the centre, and then the disk
biconcave.
In my Monograph I had separated as two different subfamilies the true
Trematodiscida (with circular concentric rings) from the Discospirida (with
spirally convoluted rings). But the enormous mass of specimens, which I
afterwards examined in the Challenger collection, has convinced me that
this separation was not natural. For in one and the same genus of most
nearly allied forms we find on one hand quite regular concentric circular
forms (_Trematodiscus_), on the other hand spirally convoluted forms
(_Discospira_), and connecting between them such forms as are in the
central part concentric, in the marginal part spiral (_Perispira_)--or
conversely, these in the centre spiral, on the margin concentric
(_Centrospira_)--and frequently also more or less irregular forms with
interrupted rings (_Atactodiscus_); therefore, all those genera (Prodromus,
1881, Nos. 448-452) have only the value of subgenera of _Porodiscus_. But a
distinct genus is _Perichlamydium_, in which the two sieve-plates run on
the margin of the lens and form a broad hyaline porous or solid girdle.
More important is the distinction of the Ommatodiscida, in which the margin
of the disk exhibits one larger osculum, armed with a corona of spines
(_Ommatodiscus_), or two oscula, opposite on the poles of one axis
(_Stomatodiscus_). Whilst in many Porodiscida all chambers of the
concentric rings lie in one and the same (equatorial) plane, in many others
with further growth they become stratified in floors, and the whole disk is
therefore composed of two to four or more parallel disks, each with a
system of concentric chambered rings or girdles, quite as in the majority
of the Coccodiscida (p. 457). Often the central part of the lenticular
disk becomes thickened by apposition of such floors or strata, whilst the
marginal part remains simple, with one single stratum. The communication
between the chambers of the different strata seems to be the same as in the
similar Coccodiscida.
Also the margin of the disk exhibits in the Porodiscida the same
characteristic {484}differences as in the foregoing family. In the
subfamily of Stylodictyida it bears a certain number of solid radial
spines, often regularly disposed (as in the Stylocyclida). In the subfamily
of Euchitonida the margin is distinguished by the possession of two to six
or more (commonly three or four) chambered arms, also situated in the plane
of the disk, and of the same structure (sometimes more or less irregular,
spongy). These arms are very variable in size, form, and structure, exhibit
the same peculiarities as in the Astracturida, and are sometimes free, at
other times connected by a "patagium" or an interbrachial spongy skeleton
of different structure, like a web membrane (compare above, p. 458). In
some genera the arms become forked or branched on the distal end.
Sometimes their distal end bears a terminal radial spine.
_The Central Capsule_ of the Porodiscida assumes generally the form of the
including shell, with or without arms, but is constantly somewhat smaller,
as it remains enclosed by the sieve-plates of the disk surface. Often the
capsule is filled with many coloured oil-globules, disposed regularly in
the chamber rows. The nucleus of it is enclosed by the central chamber, and
in many cases by this and the innermost concentric rings.
_Synopsis of the Genera of the Porodiscida._
-------------------------------------------------------------------------
I. Section of the Porodiscida--Archidiscaria.
Central chamber of the disk surrounded only by one single chambered
ring.
--------------------
1. Subfamily Archidiscida.
Only one single chambered girdle surrounds the central chamber; margin
smooth or spiny.
-------------------------------------------------------------------------
Margin smooth, without spines, 212. _Archidiscus_.
Margin armed with radial spines, 213. _Axodiscus_.
II. Section of the Porodiscida--Astrodiscaria.
Central chamber of the disk surrounded by two or more (commonly three to
six) concentric chambered rings or radiated girdles.
-------------------------------------------------------------------------
II. Section of the Porodiscida--Astrodiscaria.
Central chamber of the disk surrounded by two or more (commonly three
to six) concentric chambered rings or radiated girdles.
--------------------
2. Subfamily Trematodiscida.
Margin of the disk quite simple, without radial appendages (spines or
chambered arms), without peculiar oscula.
-------------------------------------------------------------------------
Margin simple, without an equatorial girdle, 214. _Porodiscus_.
Margin with a thin porous equatorial girdle, 215. _Perichlamydium_.
-------------------------------------------------------------------------
3. Subfamily Ommatodiscida. Margin of the disk without chambered arms but
distinguished by one or two large oscula, or wide openings armed with a
crown of spines.
-------------------------------------------------------------------------
Disk with a single marginal osculum, 216. _Ommatodiscus_.
Disk with two opposite marginal oscula, 217. _Stomatodiscus_.
-------------------------------------------------------------------------
4. Subfamily Stylodictyida.
Margin of the disk without peculiar oscular openings and without
chambered arms, but armed with solid radial spines.
-------------------------------------------------------------------------
Radial spines of the { Two opposite spines, 218. _Xiphodictya_.
margin two, three, or{
four, usually quite { Three equidistant
regularly disposed. { spines, 219. _Tripodictya_.
{
{ Four crossed spines, 220. _Staurodictya_.
Radial spines of the { Margin simple, without
margin five or more, { an equatorial girdle, 221. _Stylodictya_.
commonly irregularly {
disposed (generally {Margin with a thin porous
ten to twelve). { equatorial girdle, 222. _Stylochlamydium_.
-------------------------------------------------------------------------
5. Subfamily Euchitonida.{485}
Margin of the disk with radial chambered arms (or hollow chambered
appendages), on the distal end of the arms with or without solid
radial spines.
-------------------------------------------------------------------------
{ Two arms { Without a patagium, 223. _Amphibrachium_.
{ simple, {
Two arms, { undivided. { With a patagium, 224. _Amphymenium_.
opposite {
in one { Two arms { Without a patagium, 225. _Amphirrhopalum_.
main axis.{ forked (or {
{ one simple, {
{ other { With a patagium, 226. _Amphicraspedum_.
{ forked). {
{ { Regular, 227. _Dictyastrum_.
{ { Without a {
Three { Three arms { patagium. { Bilateral, 228. _Rhopalastrum_.
arms { simple, {
(either { undivided. {
regular, { { { Regular, 229. _Hymeniastrum_.
equal, or { { With a {
bilateral,{ { patagium. { Bilateral, 230. _Euchitonia_.
with { { {
unequal {
arms). { { Without a
{ { Either { patagium, 231. _Chitonastrum_.
{ Three arms {regular or {
{ forked. {bilateral. { With a
{ { { patagium, 232. _Trigonastrum_.
Four arms { { { Regular, 233. _Stauralastrum_.
(either { { Without a {
regular, { Four arms { patagium. { Bilateral, 234. _Hagiastrum_.
with four { simple, {
equal { undivided. { { Regular, 235. _Histiastrum_.
crossed { { With a {
arms, or { { patagium. { Bilateral, 236. _Tessarastrum_.
bilateral,{ {
with { { With a terminal
paired { { patagial girdle, 237. _Stephanastrum_
arms). {
{ { Regular, 238. _Dicranastrum_.
{ Four arms { Without a {
{ forked. { patagium. { Bilateral, 239. _Myelastrum_.
{ Five arms { Without a patagium, 240. _Pentalastrum_.
{ simple, {
Five arms { undivided. { With a patagium, 241. _Pentinastrum_.
(equal or {
unequal). { Five arms { Without a patagium, 242. _Pentophiastrum_.
{ forked. {
Six arms { Six arms { Without a patagium, 243. _Hexalastrum_.
(equal or { simple, {
unequal). { undivided. { With a patagium, 244. _Hexinastrum_.
Subfamily 1. ARCHIDISCIDA, Haeckel.
_Definition._--#Porodiscida# with a simple spherical or lenticular latticed
central chamber, surrounded by a single concentric latticed ring, which is
divided by radial beams into two to six or more radial chambers.
{486}Genus 212. _Archidiscus_,[251] n. gen.
_Definition._--#Porodiscida# with a simple central chamber, surrounded by a
single concentric ring, which is divided by radial beams into two to six or
more radial chambers, without radial spines on the margin.
The genus _Archidiscus_ begins the long and polymorphous series of the
#Cyclodiscaria# or of those #Discoidea# which do not possess the peculiar
"phacoid shell" characteristic of the three preceding families, united as
"#Phacodiscaria#." As already mentioned above, both these groups are
probably of independent origin, derived from the #Sphæroidea# in different
ways (compare pp. 402, 405, &c.). Among all #Cyclodiscaria# _Archidiscus_
is the most simple, and probably the common ancestral form, from which the
other genera may be derived.
Subgenus 1. _Dioniscus_, Haeckel.
_Definition._--Ring with two chambers, separated by two radial beams.
1. _Archidiscus dioniscus_, n. sp.
Ring circular, connected with the central chamber by two radial beams,
opposite in one axis, therefore two equal semicircular ring chambers. (This
primitive form has an interesting reference to _Saturnalis_, Pl. 13, fig.
16, and differs from it only in the lattice-work covering both faces of the
lenticular disk, the margin of which forms the ring.)
_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.016.
_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.
2. _Archidiscus dithalamus_, n. sp.
Ring roundish, connected with the central chamber by two radial beams, not
opposite in one axis; both semicircular ring chambers more or less unequal,
one of them larger than the other, and sometimes much more prominent. (If
this prominence increase, we can regard it as the beginning of spiral
convolutions, _Discospira_.)
_Dimensions._--Diameter of the ring 0.06, of the central chamber 0.014.
_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.
Subgenus 2. _Trioniscus_, Haeckel.
_Definition._--Ring with three chambers, separated by three radial beams.
{487}3. _Archidiscus trioniscus_, n. sp.
Ring triangular, roundish, equilateral, connected with the central chamber
by three radial beams at equal distances (120°); therefore three equal ring
chambers. (Resembles the central part of the disk of _Tripodictya
trigonaria_, Pl. 42, fig. 8, and may be the ancestral form of it.)
_Dimensions._--Diameter of the ring 0.04, of the central chamber 0.014.
_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.
4. _Archidiscus trithalamus_, n. sp.
Ring irregular, roundish, connected with the central chamber by three
radial beams at unequal distances; therefore three ring chambers of
different size. (If these differences be important, they introduce a spiral
convolution in the further development of the _Porodiscus_ arising from
it.)
_Dimensions._--Diameter of the ring 0.06, of the central chamber 0.016.
_Habitat._--South Pacific, Station 288, surface.
Subgenus 3. _Tetroniscus_, Haeckel.
_Definition._--Ring with four chambers, separated by four radial beams.
5. _Archidiscus stauroniscus_, n. sp. (Pl. 48, figs. 9, 9_a_).
Ring regular, square, connected with the central chamber by four radial
beams at equal distances, opposite in pairs in two axes perpendicular one
to another; therefore four equal ring chambers (or congruent quadrants of
the ring). Resembles the central part of the disk of _Staurodictya medusa_,
&c. (Pl. 42, figs. 1-3); also of _Staurodictya gracilis_, Ehrenberg, 1875
(Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. xxiii. fig. 3).
_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.016.
_Habitat._--North Pacific, Station 253, depth 3125 fathoms.
6. _Archidiscus tetroniscus_, n. sp.
Ring elliptical, of rhomboidal fundamental form, connected with the central
chamber by four radial beams, halving the sides of the rhombus and opposite
in pairs in two axes which are not perpendicular one to another; therefore
four ring chambers in pairs different, two opposite equal and larger than
the two others.
_Dimensions._--Diameter of the ring 0.05 to 0.07, of the central chamber
0.016.
_Habitat._--Central Pacific, Station 263, depth 2650 fathoms.
7. _Archidiscus tetrathalamus_, n. sp.
Ring irregular, quadrangular, connected with the central chamber by four
radial beams of increasing unequal length; therefore all four ring chambers
of different size, gradually increasing {488}in the following quadrants of
the ring. Important as an ancestral type of such spiral and semi-spiral
forms as _Staurodictya cruciata_ (Pl. 42, figs. 4, 12, &c.) and
_Stylodictya clavata_, _Stylodictya stellata_, &c., of Ehrenberg, 1875
(Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. xxiii. figs. 2, 7, 8, 9).
_Dimensions._--Diameter of the ring 0.05 to 0.08, of the central chamber
0.06.
_Habitat._--South Pacific, Station 295, depth 1500 fathoms.
Subgenus 4. _Pentoniscus_, Haeckel.
_Definition._--Ring with five chambers, separated by five radial beams.
8. _Archidiscus pentoniscus_, n. sp.
Ring pentagonal or nearly circular, regular, connected with the central
chamber by five radial beams of equal length and at equal distances (72°);
therefore all five chambers of the ring of equal size and similar form.
(Resembles the central part of the disk of _Pentinastrum asteriscus_, Pl.
44, fig. 2.)
_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.015.
_Habitat._--North Pacific, Station 244, surface.