Chapter XI: Literature and History (4)

As #Pliosphærida# (or _Sphæroidea concentrica_) we can oppose to the simple Monosphærida all other #Sphæroidea#, the lattice-shell of which is composed of two or more concentric shells, connected by radial beams. Probably all Pliosphærida (or at least the greater part of them) arise from the Monosphærida by centrifugal growth; two or more radial spines are developed from the surface of the simple lattice-sphere, and are united together by communicating lateral branches, developed at equal distances from the centre; and this same process may be repeated, two, three, four, or more times. In this way originate the characteristic systems of concentric spheres, all united by piercing radial beams which arise from the surface of the innermost sphere (not from its centre). Regarding this mode of growth, we can distinguish the innermost as "original" or "primary" shell, and all subsequent ones as "apposed" or "secondary" shells; if the number of concentric shells amount to three or more, commonly both innermost shells lie within the central capsule and are medullary shells, whilst all others lie outside it and are therefore cortical shells. This difference can be commonly recognised also in the isolated shell, without its central capsule; the distance between the cortical and the medullary shells being commonly much larger than the distance between the two medullary shells.

The #Dyosphærida#, or the #Sphæroidea# with two concentric shells, are the most numerous among the Pliosphærida. Commonly in this group the inner or primary shell lies within the central capsule as a true "medullary shell," whilst the outer lies outside it as a "cortical shell"; therefore the radial beams, connecting both, pierce the wall of the capsule. But in several forms, mainly in the peculiar group of Diplosphærida, both concentric shells remain outside the central capsule, and both are therefore "cortical shells."

The #Triosphærida#, or the #Sphæroidea# with three concentric shells, are also very rich in different forms, though not so numerous by far as the Dyosphærida. Commonly in the Triosphærida both inner shells lie within the central capsule as "medullary shells," whilst the third lies outside it as a "cortical shell"; therefore the central capsule remains intermediate in size between the outer and the middle shell. But in some genera (_e.g._, _Rhodosphæra_) both outer shells are cortical and only the {54}innermost is a medullary shell. In this case the size of the capsule remains intermediate between the inner and the middle shell.

The #Tetrasphærida#, or the #Sphæroidea# with four concentric shells, are in general not frequent, and not rich in different forms. In most of the observed species two inner shells are medullary, two outer cortical shells, the former within, the latter without, the central capsule; and the wall of the capsule, pierced by the connecting radial beams, lies between the two middle shells. But there are some Tetrasphærida in which all four shells seem to be external or cortical shells.

The #Polysphærida#, or the #Sphæroidea# with five or more concentric shells, seem of course to offer the greatest possibility for the development of very different forms; but in reality this group is the poorest and smallest of all; and only one part of it, the Arachnosphærida, is rather common. In this peculiar division the shell is composed of five to ten or more, very delicate, cobweb-like concentric shells, which are connected by radial beams; all are cortical shells, and lie outside the central capsule. Much more rare are those Polysphærida, in which both innermost shells, as true medullary shells, lie within the central capsule, all others being outside it. The total number of concentric shells in this group is commonly between five and ten, rarely more.

The #Spongosphærida# are distinguished from all other #Sphæroidea# by the spongy structure of the spherical shell, which is composed wholly or partially of an irregular spongy framework. The relation of this group to the other groups of #Sphæroidea# is probably rather complicated, for in some Spongosphærida the whole shell is composed of massive spongy reticulation, whilst in others it contains a spherical central cavity, and in a third group this cavity is filled up by one or two concentric lattice-shells, connected by radial beams. Many of these Spongosphærida are very common, and of considerable size.

The #Collosphærida# form a peculiar separate group of #Sphæroidea#, distinguished from all others by their social life or aggregation in colonies (coenobia). They represent the only group of #Sphærellaria# in which this association of numerous individual capsules or cells is realised. The shell is almost constantly simple, without regularly disposed radial spines; therefore they may be called "social Monosphærida," or better "polyzoic Ethmosphærida." Only in one small group (Clathrosphærida) the shell, enveloping every central capsule, is double or surrounded by an external mantle; these may be compared to the Diplosphærida (or better to a part of the Carposphærida, _Liosphæra_, p. 76). In most of the Collosphærida the lattice-shell is more or less irregular in form and structure.

_The Lattice Work_ of the fenestrated shells is in the #Sphæroidea# of the greatest variability, and its innumerable modifications serve mainly for the distinction of species. In general we can distinguish as the most important modifications a _regular_ network (with equal size, form, and distance of the pores or meshes) and an _irregular_ network (with {55}differences in the size, form, or distance of the meshes or pores). In both groups the pores may be either angular or round; so that there may exist together four different main forms of network--(A) regular lattice with equal hexagonal pores; (B) regular lattice with equal circular pores; (C) irregular lattice with unequal polygonal pores; (D) irregular lattice with unequal roundish pores. Besides these modifications, the pores may be prolonged into tubules which are directed radially towards the outside (rarely towards the inside) of the sphere. In other cases they are surrounded by elevated or honeycomb-like frames.

_The Radial Spines_ exhibit in the #Sphæroidea# the greatest variety in form, size, disposition, &c., and their numerous modifications serve mainly for the distinction of genera, their peculiar formation and size also for the distinction of species. In general we may distinguish as the most important modifications primary and secondary spines. The primary spines or "main spines" are commonly direct outward prolongations of the internal radial beams, connecting the concentric shells. The secondary or "by-spines" arise only from the surface of the lattice-shell, without reference to the internal beams. The by-spines are commonly smaller, and much more numerous than the main spines. Regarding the form, the radial spines are either roundish (cylindrical or conical, often also club-shaped, rarely spindle-shaped) or angular (commonly three-sided, prismatic or pyramidal). The spines are constantly solid, never hollow; the "internal canals," described by some authors, are only microscopic views of the transparent edges. In many cases the spines are branched or forked. The most important difference in the variable shape of the spines is their regular or irregular number and disposition, which afford characters for the distinction of our five families.

_The Three Dimensive Axes_--or the three diameters of the sphere, perpendicular one to another--are in the great majority of the #Sphæroidea# significant in the promorphological consideration of the body, and are indicated either by the position of the external radial spines, or at least of the internal radial beams, connecting the concentric spheres. Commonly two radial spines are placed opposite in each axis. The most perfect group in this respect seems to be that of the Cubosphærida, in which the three axes are represented by three pairs of spines. Next come the Staurosphærida, in which two axes in cross-form are exhibited by two pairs of spines. The most simple group are the Stylosphærida, in which only one pair of spines is developed, indicating one single axis. These three families form together a continuous natural series,--the #Sphæroidea# with real dimensive axes,--and exhibit at the same time relations to the three other suborders of #Sphærellaria#, the #Larcoidea#, #Discoidea#, and #Prunoidea# respectively. At both ends of this series stand two other families, on one side the Liosphærida, without any radial spines on the surface of the sphere, on the other side the Astrosphærida, in which the radial spines are developed in great and variable numbers, at least eight to twelve, commonly twenty to forty, often more than a hundred or even a thousand.

{56}The #Liosphærida# comprise all those #Sphæroidea# in which the surface of the shell is smooth, without radial spines (Pls. 12, 20). The simplest of these are the Ethmosphærida, with one single lattice-shell, enveloping the spherical central capsule. _Cenosphæra_, the most simple form of the Ethmosphærida, may be regarded as the common ancestral form of all #Sphæroidea#, in an ontogenetical as well as in a phylogenetical and morphological sense. From this simple lattice sphere all other #Sphæroidea# can be derived either by radial or by tangential growth. If the radial beams, arising from the surface of the simple fenestrated sphere, become connected (at equal distances from the centre) by tangential beams, we get the compound shells of the "Liosphærida concentrica" (with two, three, four, or more concentric spheres). The radial beams connecting these exhibit in many Liosphærida the same regular disposition and number as the external radial spines in the Astrosphærida. Perhaps these forms in a "natural system" would be better united (_e.g._, Liosphærida with twelve or twenty internal radial beams, and Astrosphærida with twelve or twenty external radial spines); but in many cases (mainly for higher numbers) the certain determination of their number and disposition is very difficult or quite impossible.

The #Cubosphærida# (Pls. 21-25) represent the large and very important family of #Sphæroidea#, in which all three dimensive axes are equally distinguished by pairs of spines, corresponding to three axes of a cube or of a regular octahedron, agreeing therefore also with the three axes of the cubic or regular crystalline system. In the majority of the Cubosphærida the six radial spines are accurately opposite each other in pairs in three axes, perpendicular one to another, and commonly they are of equal size and form; but in some genera the three pairs of spines become differentiated, whilst both spines of each pair remain equal. Either one pair is larger than the two others (which are equal), corresponding to the axes of the quadratic crystalline system; or all three pairs are different (corresponding to the three unequal axes of the rhombic crystalline system); the former nearer to the #Discoidea#, the latter to the #Larcoidea#. We may suppose with some probability, that the Cubosphærida are for the most part the common ancestral group of those #Sphæroidea#, in which a certain number of radial spines or beams is disposed in a regular order; the Staurosphærida may be derived from them by loss of one pair of spines, the Stylosphærida by loss of two pairs of spines, and most Astrosphærida by multiplying the radial spines, six to fourteen or more secondary spines being added to the six primary "dimensive spines." However, in many Astrosphærida (_e.g._, in those with eight spines, _Centrocubus_, _Octodendron_, &c.) the regular geometrical disposition of the radial spines seems to follow another mathematical order, quite independent of the Cubosphærida.

The #Staurosphærida# (Pl. 15) are distinguished by the possession of four radial spines, opposite in pairs in two axes, perpendicular one to another. This rectangular cross determines a certain plane, the "equatorial plane," and this brings the Staurosphærida near {57}to the #Discoidea#, mainly to those which also bear on the periphery of the circular equatorial plane four crossed spines (such as _Staurodisculus_, _Stethostaurus_, _Staurodictya_, &c.). But in these cruciform #Discoidea# the shell and the enclosed central capsule are discoidal or lenticular, whilst in the Staurosphærida they remain spherical. Commonly the cross is quite regular, with four right angles and four equal beams; but often also it becomes more or less irregular. In some genera one pair of equal opposite spines is larger than the other pair. These forms represent the three different axes of the rhombic crystal system, whilst the common regular Staurosphærida represent those of the quadratic crystal system. The latter can be derived from the Cubosphærida (representing the regular crystal system) by reduction of one axis and loss of its pair of spines. In general the number of species (and particularly of the individuals) is much smaller in the Staurosphærida than in all other families of #Sphæroidea#.

The #Stylosphærida# (Pls. 13-17) can be derived from the Cubosphærida by reduction of two dimensive axes and loss of two pairs of spines. Therefore, here one pair of spines only is developed, opposite in one single axis. This "monaxonial" form brings the Stylosphærida very near to the ellipsoidal #Prunoidea# (mainly to many two-spined forms of Ellipsida and Druppulida); but they differ from these by the spherical (not ellipsoidal) form of the central capsule and of the enclosing lattice-shell. In the greater part of the Stylosphærida both spines are of equal size and form, accurately opposite in the "main axis." But in many forms both spines become unequal in size or form, often very different. More rarely they are not accurately opposed, but placed in two different axes, intersecting at a small variable angle. The small group of Saturnalida presents a very remarkable and peculiar structure, in which both spines (at equal distances from the centre) are united by a circular or elliptical ring (Pl. 13, figs. 15, 16; Pl. 16, figs. 16, 17).

The #Astrosphærida# are distinguished from the other #Sphæroidea# by the great and variable number of their external radial spines (Pls. 11, 18-20, 26-30). Commonly this number amounts to from twelve to twenty, rarely to only eight to ten, very often to thirty-two to forty or more; in many species more than one hundred are present. As already mentioned above, it would be important to distinguish between primary spines (as outer prolongations of the inner radial beams) and secondary spines (developed from the surface of the shell), but in many cases this distinction is difficult or impossible. More practical is the distinction between larger "main spines" and smaller "by-spines." The size and form of the radial spines is extremely variable. Much more important is their number and disposition. In general we can here distinguish the following different cases:--(A) radial spines are developed from all the nodal points of the network on the shell surface; (B) the number of the spines is smaller than that of the nodal points, but they are irregularly scattered; (C) the radial spines exhibit a limited number and a certain regular disposition. In this latter case the following modes of distribution seem to be the most important:--(_a_) eight spines placed in the four diagonal axes of the {58}regular cube (Pl. 18, figs. 1-3); (_b_) twelve spines (placed in the corner axes of the regular icosahedron); (_c_) fourteen spines (six placed in the three dimensive axes of the regular octahedron, eight in the centres of its eight faces); (_d_) twenty spines (placed either in the same order as in many #Larcoidea# and ACANTHARIA [?], or in the twenty corners of the regular dodecahedron); (_e_) thirty-two spines (twelve placed in the twelve corners of the regular icosahedron, twenty in the centre of its triangular faces). Besides these most important and quite geometrical modes of disposition there also seem to occur in the Astrosphærida the following subregular (or symmetrical?) modes: 9, 10, 16, 18, 24, 40, 60, 80. But it is very difficult to give a correct account of these modes. In every case this manifold and regular disposition of the radial spines is of the highest interest for the study of general "Promorphology."

_The Central Capsule_ is in all #Sphæroidea# (without any exception) a perfect sphere in the geometrical sense, even in those forms in which the enclosing lattice-shell is more or less irregular (_i.e._, many Collosphærida). This is the most important character, which separates the #Sphæroidea# from all other #Sphærellaria#. For in the #Prunoidea# the capsule is ellipsoidal, with one prolonged axis; in the #Discoidea# lenticular, with one shortened axis; in the #Larcoidea# lentelliptical, with three different dimensive axes. The central capsule is originally always enclosed by the lattice-shell; but in many cases with increasing growth this relation becomes inverted; the capsule sending out many club-shaped blind sacs through the meshes of the lattice-shell, and these melting together outside the latter, a new membrane is formed, enclosing a "medullary shell."

_The Nucleus_ of the cell exhibits a very different shape in the solitary and the social #Sphæroidea#. In the solitary or monozoic #Sphæroidea# the centre of the central capsule is occupied by a large spherical concentric nucleus, with or without nucleoli; also this nucleus is originally always within the innermost lattice-shell, but with increasing size may overgrow and enclose it. A short time before the formation of the vibratile spores the central nucleus becomes resolved into many small nuclei. In the social or polyzoic #Sphæroidea#--the Collosphærida--commonly the simple central nucleus very early (a long time before the formation of the spores) is divided into a great number of small nuclei, whilst the centre of the capsule becomes filled with a large oil-globule. Therefore we find the same difference between the solitary and social forms in the #Sphæroidea# as in the #Colloidea#. Here also the calymma, or the jelly-mantle, enveloping the central capsule, is in the social forms very large and voluminous, differentiated into alveoles, whilst in the solitary forms it is much smaller, without alveoles.

{59}_Synopsis of the Families of_ #Sphæroidea#.

{ A. Liosphærida { Spherical shell
{ monozoa. { commonly
{ Single cells { quite regular,
{ (each with shell) { simple, or
Surface of { living solitary. { composed of
the spherical { { two or more
shell smooth, { { concentric
rough, or { { spheres, 5. LIOSPHÆRIDA.
thorny, but {
not armed { B. Liosphærida { Spherical shell
with radial { polyzoa. { commonly
spines. { Aggregated cells { more or less
{ (each with { irregular,
{ shell) living { simple (rarely
{ in colonies. { composed of
{ { two concentric
{ { spheres), 6. COLLOSPHÆRIDA.

Surface of { Two radial main-spines, opposite in
the spherical { one axis of the shell 7. STYLOSPHÆRIDA.
shell armed {
with two, { Four radial main-spines, opposite in
four, or six { pairs in two dimensive axes,
radial main { perpendicular one to another, 8. STAUROSPHÆRIDA.
spines, {
opposite in { Six radial main-spines, opposite in
pairs in one, { pairs in three dimensive
two, or three { axes (perpendicular one to
dimensive { another), 9. CUBOSPHÆRIDA.
axes (always {
solitary). {

Surface of the spherical shell covered with numerous
(commonly irregularly disposed) radial spines,
often also twelve to twenty, more or less regularly
disposed, 10. ASTROSPHÆRIDA.

Family V. #LIOSPHÆRIDA#, Haeckel, 1881.

_Liosphærida_, Haeckel, 1881, Prodromus, p. 449.

_Definition._--#Sphæroidea# without radial spines on the surface of the spherical shell; living solitary (not associated in colonies).

The family #Liosphærida# comprises all those solitary #Sphæroidea# in which the surface of the spherical shell is not armed with radial spines. Nearly the half of this large group is formed by the Ethmosphærida, in which the carapace is a quite simple, spherical lattice-shell; this subfamily is probably the common ancestral group from which all other #Sphæroidea#, or even all #Sphærellaria#, can be derived in a phylogenetical as well as in a morphological sense. The central capsule in this first subfamily is constantly enclosed by the fenestrated shell, and separated from it by the jelly-veil. The shell is therefore an extracapsular or medullary shell.

To these simple Ethmosphærida all other subfamilies can be opposed as "Liosphærida concentrica," as their carapace is composed of two or more concentric lattice-shells; two in the Carposphærida, three in the Thecosphærida, four in the Cromyosphærida, five or more in the Caryosphærida. In all these four subfamilies the concentric shells are simple (not spongy) fenestrated shells. In a sixth subfamily, in the Plegmosphærida, the shell is wholly or partially composed of spongy wicker-work, with or without a latticed medullary shell in the centre.

The internal radial beams, in the "Liosphærida composita" connecting the concentric spheres, exhibit in their number and disposition similar important differences, such as the external radial spines in the Astrosphærida. The following eight {60}different cases of regular disposition were observed:--(A) two opposite beams in one axis; (B) four beams, opposite in pairs in two axes perpendicular one to another; (C) six beams, opposite in pairs in the three dimensive axes; (D) eight beams, opposite in pairs in the four diagonals of the regular cube; (E) twelve beams corresponding to the twelve axes of the regular icosahedron; (F) fourteen beams quite regularly disposed (six corresponding to the three axes of the regular octahedron, eight to the central points of its faces); (G) twenty beams (probably corresponding to the twenty corners of a regular dodecahedron); (H) thirty-two beams, regularly disposed. Rarely the number of the radial beams is intermediate between these eight cases, and rarely it is higher; then commonly the disposition is irregular. The regularity of their disposition in the great majority of cases is very remarkable and evident.

_Synopsis of the Genera of Liosphærida._

-------------------------------------------------------------------------
I. Subfamily Ethmosphærida.
(Shell one single latticed sphere.)
-------------------------------------------------------------------------
{Shell cavity
{ simple, 15. _Cenosphæra_.
Pores of the {
shell simple, {Shell cavity
not prolonged { with radial
into free tubuli. { beams united
{ in the
{ centre, 16. _Stigmosphæra_.

Pores prolonged {Tubuli external,
into free { centrifugal, 17. _Ethmosphæra_.
conical or {
cylindrical {Tubuli internal,
tubuli. { centripetal, 18. _Sethosphæra_.
-------------------------------------------------------------------------
II. Subfamily Carposphærida.
(Two concentric spheres.)
-------------------------------------------------------------------------
One shell medullary (intracapsular),
the other cortical (extracapsular), 19. _Carposphæra_.

Both shells cortical
(near together), 20. _Liosphæra_.
-------------------------------------------------------------------------
III. Subfamily Thecosphærida.
(Three concentric spheres.)
-------------------------------------------------------------------------
Two shells medullary
(intracapsular), one shell
cortical (extracapsular), 21. _Thecosphæra_.

One shell medullary (intracapsular),
two shells cortical
(extracapsular), 22. _Rhodosphæra_.
-------------------------------------------------------------------------
IV. Subfamily Cromyosphærida.
(Four concentric spheres.)
-------------------------------------------------------------------------
Two inner medullary shells
(intracapsular), and two outer
cortical shells (extracapsular), 23. _Cromyosphæra_.
-------------------------------------------------------------------------
V. Subfamily Caryosphærida.
(Five or more concentric spheres.)
-------------------------------------------------------------------------
Two inner medullary shells, and
three or more outer cortical
shells, 24. _Caryosphæra_.
-------------------------------------------------------------------------
VI. Subfamily Plegmosphærida.
(Spherical shell wholly or partially of spongy structure.)
-------------------------------------------------------------------------
Spongy sphere {Sphere solid, 25. _Styptosphæra_.
without latticed {
medullary shell {Sphere with a
in the centre. { central cavity, 26. _Plegmosphæra_.

Spongy sphere with {One single
one or two { medullary shell, 27. _Spongoplegma_.
latticed {
medullary shells {Two concentric
in the centre. { medullary
{ shells, 28. _Spongodictyon_.

{61}Subfamily ETHMOSPHÆRIDA,[25] Haeckel, 1862, Monogr. d. Radiol., p. 348 (_sensu restricto_).

_Definition._--#Liosphærida# with one single spherical lattice-shell; living solitary, not aggregated in colonies.

Genus 15. _Cenosphæra_,[26] Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 237.

_Definition._--#Liosphærida# with one single latticed sphere, with simple shell-pores (not prolonged into free tubuli) and with simple shell-cavity (without internal radial beams).

The genus _Cenosphæra_ is the most simple form of all SPHÆROIDEA, and may be regarded as the common ancestral form of this order. The siliceous latticed shell, in which the central capsule is enclosed, represents a simple regular sphere, with simple cavity. The pores of the shell-wall are simple, not prolonged into radial tubuli (as in _Ethmosphæra_ and _Sethosphæra_). According to the different form of the pores, the numerous species of this genus can be disposed in four different subgenera. Some species may be easily confounded with isolated shells of the corresponding social _Collosphæra_; but in this latter the spherical shell-form is commonly more or less irregular, in _Cenosphæra_ quite regular.

Subgenus 1. _Phormosphæra_, Haeckel, 1881, Prodromus, p. 448.

_Definition._--Pores of the shell regular or subregular, hexagonal or circular, with hexagonal frames or lobes; all nearly of equal size and form.

1. _Cenosphæra primordialis_, n. sp.

Shell very thin walled, smooth. Pores hexagonal, regular, or subregular; twelve to fifteen on the half meridian of the shell; bars between them extremely delicate (only visible when three hundred or four hundred times enlarged). Diameter of the shell nine to ten times that of the meshes. This species is remarkable for the extreme delicacy of the arachnoidal network of the simple spherical shell; it may be regarded as the common ancestral form of all #Sphæroidea#. The shell equals that of _Heliosphæra tenuissima_ (figured in my Monograph, 1862, pl. ix. fig. 2), but differs from it by the smooth surface and the absence of all spines or thorns. I observed this species living in the Indian Ocean, near Ceylon, in 1882; the spherical diameter of the central capsule is about one-third of that of the shell; the contents of the central capsule are colourless {62}and transparent, except the central dark globular nucleus. The same shells also occur in some mounted preparations of surface organisms from the Challenger.

_Dimensions._--Diameter of the shell 0.12, of the pores 0.012.

_Habitat._--Indian Ocean, Ceylon, Haeckel; Central Pacific, Stations 266, 271, surface.

2. _Cenosphæra inermis_, Haeckel.

_Heliosphæra inermis_, Haeckel, 1862, Monogr. d. Radiol., p. 351, Taf.
ix. fig. 1.

Surface of the thin-walled shell smooth. Pores regular, hexagonal, twelve to fifteen times as broad as the bars, seven to nine on the quadrant.

_Dimensions._--Diameter of the shell 0.08 to 0.12, pores 0.012 to 0.015, bars 0.001.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

3. _Cenosphæra hexagonalis_, n. sp.

Surface of the thick-walled shell smooth. Pores regular, hexagonal, five to six times as broad as the bars, six to eight on the quadrant.

_Dimensions._--Diameter of the shell 0.1 to 0.15, pores 0.01 to 0.012, bars 0.002.

_Habitat._--Central Pacific, Stations 265 to 274, at various depths.

4. _Cenosphæra mellifica_, n. sp. (Pl. 12, fig. 9).

Surface of the thick-walled shell smooth. Pores regular, circular, with thin hexagonal frames, four times as broad as the bars, six to eight on the quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.12, bars 0.003.

_Habitat._--South Pacific, Station 288, surface.

5. _Cenosphæra favosa_, n. sp. (Pl. 12, fig. 10).

Surface of the thick-walled shell rough. Pores regular, circular, with thin hexagonal frames, three times as broad as the bars, ten to twelve on the quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.09, bars 0.003.

_Habitat._--North Atlantic, Færöe Channel (Gulf Stream), John Murray, surface.

6. _Cenosphæra vesparia_, n. sp. (Pl. 12, fig. 11).

Surface of the thick-walled shell smooth. Pores regular, circular, with thick hexagonal frames, twice as broad as the bars, ten to twelve on the quadrant.

_Dimensions._--Diameter of the shell 0.25, pores 0.016, bars 0.008.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms, and surface.

{63}7. _Cenosphæra bombus_, n. sp.

Shell thick walled, rough. Pores regular, circular, with thin hexagonal frames, of the same breadth as the bars, twenty to twenty-two on the quadrant.

_Dimensions._--Diameter of the shell 0.3, pores and bars 0.005.

_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms.

8. _Cenosphæra melecta_, n. sp.

Shell thick walled, papillate. Pores regular, circular, double-edged, with thick hexagonal frames, of the same breadth as the bars; a short conical papilla in the corner of each hexagon; fourteen to sixteen pores on the quadrant.

_Dimensions._--Diameter of the shell 0.2, pores and bars 0.008.

_Habitat._--Fossil in Barbados.

9. _Cenosphæra anthophora_, n. sp.

Shell thick walled, papillate. Pores regular, circular, with an elegant six-lobed frame and a coronal of six short papillæ; the latter alternating with the six lobes (quite as in Pl. 28, fig. 1_b_). Pores twice as broad as the bars, ten to twelve on the quadrant.

_Dimensions._--Diameter of the shell 0.13, pores 0.01, bars 0.005.

_Habitat._--Central Pacific, Station 271, surface.

10. _Cenosphæra rosetta_, n. sp.

Shell thin walled, smooth. Pores regular, circular, with an elegant six-lobed outer opening, without papillæ. Pores of the same breadth as the bars, six to eight on the quadrant.

_Dimensions._--Diameter of the shell 0.1, pores and bars 0.006.

_Habitat._--South Atlantic, Station 323, depth 1900 fathoms.

Subgenus 2. _Circosphæra_, Haeckel.

_Definition._--Pores of the spherical shell regular or subregular, circular, without hexagonal frames or lobes, all nearly of equal size and form.

11. _Cenosphæra porophæna_, Ehrenberg.

_Cenosphæra porophæna_, Ehrenberg, 1858, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 31.

Shell thin walled, smooth. Pores regular, circular, six to eight times as broad as the bars, five to six on the quadrant.

_Dimensions._--Diameter of the shell 0.1, pores 0.012, bars 0.002.

_Habitat._--Mediterranean (Crete, depth 1100 fathoms; Corfu, surface).

{64}12. _Cenosphæra setosa_, Ehrenberg.

_Cenosphæra setosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 287, Taf. vii. fig. 1.

Shell thin walled, covered with very short and numerous bristles. Pores regular, circular, five to six times as broad as the bars, six to eight on the quadrant.

_Dimensions._--Diameter of the shell 0.17, pores 0.2, bars 0.03.

_Habitat._--West Tropical Pacific, 3300 fathoms; Philippine Sea, Station 200, depth 250 fathoms.

13. _Cenosphæra plutonis_, Ehrenberg.

_Cenosphæra plutonis_, Ehrenberg, 1854, Mikrogeol., Taf. xxxv. B, B. iv.
fig. 20.

Shell thin walled, covered with short conical papillæ. Pores regular, circular, twice as broad as the bars, eight to nine on the quadrant.

_Dimensions._--Diameter of the shell 0.09, pores 0.006, bars 0.003.

_Habitat._--North Atlantic, Station 353, depth 2965 fathoms.

14. _Cenosphæra proserpinæ_, n. sp.

Shell thin walled, smooth. Pores regular, circular, four times as broad as the bars, five to six on the quadrant.

_Dimensions._--Diameter of the shell 0.08, pores 0.008, bars 0.002.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

15. _Cenosphæra eridani_, n. sp.

Shell thin walled, smooth. Pores regular, circular, three times as broad as the bars, eleven to twelve on the quadrant.

_Dimensions._--Diameter of the shell 0.16, pores 0.01, bars 0.003.

_Habitat._--South Pacific, Station 295, depth 1500 fathoms.

16. _Cenosphæra lethe_, n. sp.

Shell thick walled, smooth. Pores regular, circular, double-edged, five times as broad as the bars, sixteen to eighteen on the quadrant.

_Dimensions._--Diameter of the shell 0.25, pores 0.01, bars 0.002.

_Habitat._--North Atlantic, Station 64, depth 2700 fathoms.

17. _Cenosphæra elysia_, n. sp. (Pl. 12, fig. 8).

Shell thick walled, rough. Pores regular, circular, double-edged, twice as broad as the bars, twelve to fourteen on the quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.01, bars 0.005.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.

{65}18. _Cenosphæra nirwana_, n. sp.

Shell thick walled, smooth. Pores regular, circular, twice as broad as the bars, twenty-four to twenty-five on the quadrant.

_Dimensions._--Diameter of the shell 0.25, pores 0.004, bars 0.002.

_Habitat._--Indian Ocean, Belligemma, Ceylon, surface; Haeckel.

19. _Cenosphæra maxima_, n. sp.

Shell thick walled, smooth. Pores regular, circular, twice as broad as the bars, thirty to thirty-three on the quadrant.

_Dimensions._--Diameter of the shell 0.3 to 0.4, pores 0.012, bars 0.006.

_Habitat._--West Tropical Pacific, Station 225, depth 4475; also fossil in Barbados.

20. _Cenosphæra compacta_, n. sp. (Pl. 12, fig. 7).

Shell very thick walled, rough (its wall one-fourth to one-third as thick as the radius). Pores subregular, circular, of the same breadth as the bars, seven to eight on the quadrant.

_Dimensions._--Diameter of the shell 0.15, pores and bars 0.012.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

_Cenosphæra radiata_, Zittel, 1876 (L. N. 29, p. 84, Taf. ii. figs. 7, 8), a fossil Cretaceous species, is closely allied to _Cenosphæra compacta_.

21. _Cenosphæra crassa_, n. sp.

Shell very thick walled, rough (its wall nearly half as thick as the radius). Pores tubular, double-edged, regular, circular, ten times as broad as the thin united bars, twelve to fourteen on the quadrant.

_Dimensions._--Diameter of the shell 0.14, pores 0.01, bars 0.001.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

22. _Cenosphæra solida_, n. sp.

Shell very thick walled, covered with innumerable short bristles (its wall one-third as thick as the radius). Pores regular, circular, four times as broad as the bars, tubular, eight to ten on the quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.02, bars 0.005.

_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms.

Subgenus 3. _Cyrtidosphæra_, Haeckel, 1862, Monogr. d. Radiol., p. 348.

_Definition._--Pores of the spherical shell irregularly polygonal, of unequal size or form, sometimes roundish with polygonal frames.

{66}23. _Cenosphæra reticulata_, Haeckel.

_Cyrtidosphæra reticulata_, Haeckel, 1862, Monogr. d. Radiol., p. 349,
Taf. xi. fig. 2.

Shell very thin walled, smooth. Pores irregular, polygonal, two to eight times as broad as the bars, fifteen to twenty on the quadrant (groups of four to eight smaller meshes are scattered on the surface, and separated by reticular rows of larger meshes).

_Dimensions._--Diameter of the shell 0.16, pores 0.004 to 0.016, bars 0.002.

_Habitat._--Mediterranean (Messina), surface.

24. _Cenosphæra tenerrima_, n. sp.

Shell extremely thin walled, smooth, like a cobweb. Pores very irregular and small, polygonal with thread-like bars, thirty to forty on the quadrant.

_Dimensions._--Diameter of the shell 0.25, pores 0.002 to 0.008, bars under 0.001.

_Habitat._--Central Pacific, Station 271, surface.

25. _Cenosphæra polygonalis_, n. sp.

Shell thin walled, smooth, with irregular, polygonal pores, three to four times as broad as the bars, eight to ten on the quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.012 to 0.02, bars 0.005.

_Habitat._--North Pacific, Station 236, surface.

26. _Cenosphæra papillata_, n. sp.

Shell thick walled, covered with short conical papillæ. Pores irregular, polygonal, three to five times as broad as the bars, fourteen to sixteen on the quadrant.

_Dimensions._--Diameter of the shell 0.12, pores 0.004 to 0.007, bars 0.0015.

_Habitat._--South Atlantic, Station 325, surface.

27. _Cenosphæra cristata_, n. sp.

Shell thick walled, rough. Pores irregular, roundish, surrounded by polygonal crested frames two to three times as broad as the bars, eight to twelve on the quadrant.

_Dimensions._--Diameter of the shell 0.16, pores 0.006 to 0.01, bars 0.003.

_Habitat._--North Pacific, Station 254, surface.

28. _Cenosphæra perforata_, n. sp. (Pl. 26, fig. 10).

_Ceriosphæra perforata_, Haeckel, 1881, Prodromus et Atlas, _loc. cit._

Shell thick walled, rough. Pores irregular, roundish, surrounded by high polygonal funnel-shaped frames, which are solid in the inner half, perforated by numerous very small pores in the {67}outer half, sieve-shaped. Pores one to three times as broad as the bars, of very different size, four to six on the quadrant.

_Dimensions._--Diameter of the shell 0.15, pores 0.01 to 0.02, bars 0.005 to 0.01.

_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms.

29. _Cenosphæra coronata_, n. sp. (Pl. 26, fig. 11).

Shell thick walled, rough. Pores irregular, roundish, surrounded by high polygonal frames bearing on their sharp crest a series of small papillæ, so that each pore is surrounded by a coronal of such spinules. Pores four to eight times as broad as the bars, four to five on the quadrant.

_Dimensions._--Diameter of the shell 0.15, pores 0.01 to 0.03, bars 0.002 to 0.008.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

Subgenus 4. _Porosphæra_, Haeckel.

_Definition._--Pores of the spherical shell irregular, roundish, without polygonal frames, of unequal size or form.

30. _Cenosphæra antiqua_, Haeckel.

_Cenosphæra plutonis_, var., Dunikowski, 1882, Denkschr. d. k. Akad. d.
Wiss. Wien, Bd. xlv. p. 25, Taf. iv. figs. 47, 48.

_Cenosphæra plutonis_, var., Stöhr, 1880, Palæontogr. xxvi. p. 85, Taf.
i. fig. 1.

Shell thin walled, smooth. Pores irregular, roundish, two to eight times as broad as the bars, ten to fifteen on the quadrant.

_Dimensions._--Diameter of the shell 0.15 to 0.2, pores 0.007 to 0.015, bars 0.002 to 0.008.

_Habitat._--Fossil in the Jurassic, Cretaceous, and Tertiary formations; living in the depths of the Atlantic and Pacific; Station 332, depth 2200 fathoms; Station 225, depth 4475 fathoms, &c.

31. _Cenosphæra gigantea_, n. sp.

Shell thick walled, smooth. Pores irregular, roundish, two to five times as broad as the bars, thirty to forty on the quadrant.

_Dimensions._--Diameter of the shell 0.4 to 0.5, pores 0.004 to 0.01, bars 0.002.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms; also fossil in Barbados.

32. _Cenosphæra marginata_, n. sp.

Shell very thick walled, smooth. Pores irregular, roundish, double-edged, three to eight times as broad as the bars, six to eight on the quadrant.

{68}_Dimensions._--Diameter of the shell 0.12, pores 0.01 to 0.03, bars 0.004.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.

33. _Cenosphæra aspera_, Stöhr.

_Cenosphæra aspera_, Stöhr, 1880, Palæontogr. Bd. xxvi. p. 85, Taf. i.
fig. 2.

Shell thick walled, rough, covered with short conical papillæ. Pores irregular, roundish, of about the same breadth as the bars, eight to twelve on the quadrant.

_Dimensions._--Diameter of the shell 0.17, pores and bars 0.01 to 0.04.

_Habitat._--Fossil in Tertiary rocks of Sicily; Grotte, Stöhr.

34. _Cenosphæra hirsuta_, Ehrenberg.

_Cenosphæra hirsuta_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.,
Berlin, p. 287, Taf. x. fig. 18.

Shell thin walled, rough, covered with innumerable very short bristles. Pores very irregular, roundish, of about the same breadth as the bars.

_Dimensions._--Diameter of the shell 0.11, pores and bars 0.002 to 0.012.

_Habitat._--Indian Ocean, Zanzibar, Pullen; depth 2200 fathoms.

Genus 16. _Stigmosphæra_,[27] Haeckel, n. gen.

_Definition._--#Liosphærida# with one single latticed sphere, with simple shell-pores (not prolonged into free tubuli); in the central point of the spherical shell-cavity are united a number of radial beams, which become forked and inserted into the inner surface of the shell by their distal ends.

The genus _Stigmosphæra_ differs from _Cenosphæra_ (and from all other Monosphærida) by internal radial beams, which are united in the centre of the simple spherical shell; these beams are branched, and the distal ends of the branches inserted on the internal surface of the shell. I have observed only two, nearly identical specimens of this genus, both with regular, hexagonal pores and thin bars; the beams were implanted in the corners of the hexagons. In one specimen the surface was covered with short radial bristles, whilst these in the other specimen were prolonged into radial spines (like _Acanthosphæra_). Possibly this peculiar genus is derived from _Carposphæra_, by reduction and loss of a central medullary shell.

_Stigmosphæra actinocentra_, n. sp.

Shell very thin walled, rough, with regular circular, hexagonally framed pores, six times as broad as the bars, eight to ten on the quadrant; in the corner of each hexagon a small bristle. In {69}the central point of the shell are united about twelve (?) thin and straight radial beams, which are forked, with dichotomous branches; the distal ends of the branches are inserted in the corners of the hexagons on the inside of the shell.

_Dimensions._--Diameter of the shell 0.15, pores 0.02, bars 0.003.

_Habitat._--Central Pacific, Station 271, surface.

Genus 17. _Ethmosphæra_,[28] Haeckel, 1862, Monogr. d. Radiol., p. 349.

_Definition._--#Liosphærida# with one single latticed sphere, with simple shell-cavity; with shell-pores which are prolonged on the outside in centrifugal, conical, or cylindrical tubuli.

The genus _Ethmosphæra_ differs from the simple _Cenosphæra_, its ancestral form, by the peculiar formation of the shell-pores; in all observed species of the genus these are quite regular, of nearly equal size and form; their base in the spherical shell-face is hexagonal, but on the outside prolonged into centrifugal, external, radial tubuli, which are either conical or cylindrical (in the latter case both openings of the tubes being equal, in the former the outer opening being smaller than the inner). The solitary _Ethmosphæra_ corresponds to the social _Siphonosphæra_; but in the former the formation of the shell and of its tubuli is quite regular, in the latter more or less irregular.

Subgenus 1. _Ethmosphærella_, Haeckel.

_Definition._--Tubuli conical, their outer opening smaller than the inner.

1. _Ethmosphæra siphonophora_, Haeckel.

_Ethmosphæra siphonophora_, Haeckel, 1862, Monogr. d. Radiol., p. 350,
Taf. xi. fig. 1.

Tubuli conical, their outer opening half as broad as the inner and three times as broad as their height. Five to six pores on the quadrant. Diameter of the outer pores one and a half times as large as their distance from each other.

_Dimensions._--Diameter of the shell 0.1, outer pores 0.01, their distance 0.007.

_Habitat._--Mediterranean (Messina), surface, Haeckel.

2. _Ethmosphæra conosiphonia_, n. sp. (Pl. 12, figs. 5, 5_a_).

Tubuli conical, their outer opening two thirds as broad as the inner, and scarcely broader than their height. Ten to twelve pores on the quadrant. Diameter of the outer pores twice as large as their distance from each other.

_Dimensions._--Diameter of the shell 0.17, outer pores 0.01, their distance 0.005.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

{70}3. _Ethmosphæra polysiphonia_, n. sp. (Pl. 12, fig. 6).

Tubuli conical, their outer opening three-fourths as broad as the inner and three times as broad as their height. Sixteen to eighteen pores on the quadrant. Diameter of the outer pores three times as large as their distance apart.

_Dimensions._--Diameter of the shell 0.2, outer pores 0.008, their distance 0.003.

_Habitat._--West Tropical Pacific, Station 225, depth 4475 fathoms; also fossil in Barbados and in Sicily.

Subgenus 2. _Ethmosphæromma_, Haeckel.

_Definition._--Tubuli cylindrical, their outer opening about as large as the inner.

4. _Ethmosphæra stenosiphonia_, n. sp.

Tubuli cylindrical, short, quite contiguous, so that their diameter is six times as large as their distance apart, but about equal to their height. Nine to ten pores on the quadrant.

_Dimensions._--Diameter of the shell 0.14, outer pores 0.012, their distance 0.002.

_Habitat._--Central Pacific, Station 271, surface.

5. _Ethmosphæra pachysiphonia_, n. sp.

Tubuli cylindrical, twice as long as broad, very thick-walled, and nearly contiguous, so that their diameter is five times as large as their distance apart. The thickness of their wall is equal to their lumen. Twelve to fourteen pores on the quadrant.

_Dimensions._--Diameter of the shell 0.16, outer pores 0.01, their distance 0.002.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

6. _Ethmosphæra leptosiphonia_, n. sp.

Tubuli cylindrical, short, about as long as broad, very thin-walled and fragile, separated by wide distances, which are three times as large as their diameter. Six to seven pores on the quadrant. (Very similar to _Siphonosphæra cyathina_, Pl. 6, fig. 10, but quite regular, all tubuli retaining the same size and distance.)

_Dimensions._--Diameter of the shell 0.12, outer pores 0.01, their distance 0.03.

_Habitat._--North Atlantic, Færöe Channel, John Murray; surface.

7. _Ethmosphæra macrosiphonia_, n. sp.

Tubuli cylindrical, very elongated, four times as long as broad; their bases separated by distances which are equal to their breadth. Eight to ten tubuli on the quadrant. (The tubes are similar to those of _Siphonosphæra serpula_, Pl. 6, fig. 6, but quite regular, straight, not curved, all of the same size and at equal distances apart.)

{71}_Dimensions._--Diameter of the shell 0.1, length of the tubes 0.04, breadth 0.01, basal distance 0.01.

_Habitat._--Indian Ocean, Cocos Islands, surface, Rabbe.

Genus 18. _Sethosphæra_,[29] Hæckel, 1881, Prodromus, p. 452 (_sensu emendato_).

_Definition._--#Liosphærida# with one single latticed sphere, with simple shell-cavity; with shell-pores, which are prolonged on the inside into centripetal, conical, or cylindrical tubuli.

The genus _Sethosphæra_ differs from its ancestral form, _Cenosphæra_, by the production of internal, centripetal, radial tubuli on the inside of the shell (the contrary of the preceding genus _Ethmosphæra_). It corresponds therefore to the social _Pharyngosphæra_; but in the latter the formation of the shell and its tubes is more or less irregular, whilst in the former each regular pore is prolonged into a regular tubule.

1. _Sethosphæra entosiphonia_, n. sp.

Shell with smooth surface and regular circular pores, separated by hexagonal frames, twice as broad as the bars. Six to eight on the quadrant. Each pore is prolonged on the inside of the shell in a short conical centripetal tube, twice as long as its diameter.

_Dimensions._--Diameter of the shell 0.15, outer pores 0.008, bars 0.004, length of the tubuli 0.015.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

2. _Sethosphæra entosolenia_, n. sp.

Shell with smooth surface and regular circular pores, without hexagonal frames, of about the same breadth as the bars. Ten to twelve on the quadrant. Each pore is prolonged on the inside of the shell into a thin cylindrical centripetal tube, three times as long as its diameter.

_Dimensions._--Diameter of the shell 0.2, outer pores and bars 0.006, length of the tubuli 0.02.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

Subfamily CARPOSPHÆRIDA,[30] Haeckel, 1881, Prodromus, p. 449.

_Definition._--#Liosphærida# with two concentric spherical lattice-shells, which are united by radial beams.

_Carposphæra_,[31] Haeckel, 1881, Prodromus, p. 451.

_Definition._--Liosphærida with one medullary (intracapsular) and one cortical (extracapsular) shell, both connected by radial beams piercing the central capsule.

{72}The genus _Carposphæra_ comprises a large number of double-shelled #Sphæroidea#, formerly united with _Haliomma_, but different from this genus by the absence of radial spines. The shell is composed of two concentric latticed spheres, the inner of which (or the medullary shell) is situated within the central capsule, the other (or the cortical shell) outside it. Both shells are connected by radial beams which pierce the wall of the central capsule. The distance between the shells is at least as large as (commonly much larger than) the radius of the inner shell, whilst in the following genus, _Liosphæra_, that distance is much smaller than this radius.

Subgenus 1. _Melittosphæra_, Haeckel, 1881, Prodromus, p. 451.

_Definition._--Pores of the cortical shell regular, hexagonal (or circular, with hexagonal frames or lobes), all of nearly equal size and form.

1. _Carposphæra capillacea_, n. sp.

Cortical shell very delicate, four times as broad as the similarly constructed medullary shell, with regular hexagonal meshes (twenty to twenty-five on the quadrant) and very thin thread-like bars. Both shells connected by twenty (?) very thin radial beams. (Similar to _Heliosoma radians_, Pl. 28, fig. 3, 3_a_, but with smooth surface, without any radial spines.)

_Dimensions._--Diameter of the outer shell 0.2, inner 0.05, pores 0.01, bars below 0.001.

_Habitat._--Central Pacific, Station 274, surface.

2. _Carposphæra cubaxonia_, n. sp.

Cortical shell smooth, three times as broad as the medullary shell, with regular hexagonal pores, four times as broad as the bars. Eight to ten pores on the quadrant. Medullary shell with regular circular pores, twice as broad as the bars. Both shells connected by six radial beams, which are three-sided prismatical, opposite in pairs in the three dimensive axes.

_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; outer pores 0.01, inner 0.005.

_Habitat._--South Pacific, Station 291, surface.

3. _Carposphæra infundibulum_, Haeckel.

_Haliomma infundibuliforme_, Stöhr, 1880, Palæontogr. Bd. xxvi. p. 87,
Taf. i. fig. 6.

Cortical shell very thick-walled, two and a half times as broad as the medullary shell, with rough surface and regular hexagonal, funnel-shaped pores, of about the same breadth as the bars. Five to six on the quadrant.

_Dimensions._--Diameter of the outer shell 0.1, inner 0.04, outer pores and bars 0.01.

_Habitat._--North Atlantic, Station 354; fossil in Tertiary rocks (Barbados and Sicily).

{73}4. _Carposphæra melissa_, n. sp.

Cortical shell thick walled, four times as broad as the medullary shell, with regular circular, hexagonally framed pores, three times as broad as the bars. Eight to ten pores on the quadrant. Medullary shell with simple circular pores.

_Dimensions._--Diameter of the outer shell 0.16, inner 0.04, outer pores 0.012, bars 0.004.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

5. _Carposphæra melitomma_, n. sp. (Pl. 20, fig. 4).

_Melitomma melittosphæra_, Haeckel, 1881; Prodromus et Atlas, _loc. cit._

Cortical shell thick walled, with thorny surface, two and a half times as broad as the medullary shell. Its pores regular, circular, twice as broad as the bars, elegantly six-lobed, separated by crested hexagonal frames; in each hexagon-corner a short conical papilla (alternating with a lobe). Eight to ten pores on the quadrant. Medullary shell with small simple circular pores.

_Dimensions._--Diameter of the outer shell 0.17, inner 0.07, outer pores 0.01, bars 0.005, inner pores 0.005.

_Habitat._--Central Pacific, Stations 266 to 274, in various depths.

Subgenus 2. _Cerasosphæra_, Haeckel, 1881, Prodromus, p. 451.

_Definition._--Pores of the cortical shell regular, circular, without hexagonal frames, all of nearly equal size and form.

6. _Carposphæra cerasus_, n. sp.

Cortical shell thin walled, smooth, twice as broad as the medullary shell; both with regular circular pores, six times as broad as the bars. Twelve to fifteen pores on the quadrant. Outer pores twice as large as the inner.

_Dimensions._--Diameter of the outer shell 0.24, inner 0.12; outer pores 0.016, inner 0.008.

_Habitat._--Central Pacific, Station 271, surface.

7. _Carposphæra apiculata_, Haeckel.

? _Haliomma apiculatum_, Ehrenberg, 1872; Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 313.

Cortical shell thin-walled, covered with numerous short conical thorns, three times as broad as the medullary shell. Pores regular, circular, four times as broad as the bars. Six to eight pores on the quadrant.

_Dimensions._--Diameter of the outer shell 0.15, inner 0.05, outer pores 0.012, bars 0.03.

_Habitat._--North Pacific, California, depth 2000 fathoms; Station 254, depth 3025 fathoms.

{74}8. _Carposphæra entactinia_, Haeckel.

_Haliomma entactinia_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 74, Taf. xxvi. fig. 4.

Cortical shell thick walled, rough, twice as broad as the medullary shell; both shells with regular circular pores, twice as broad as the bars. Six to eight pores on the quadrant. Outer pores half as broad as the inner. Both shells connected by very numerous (twenty-four to forty-eight or more) radial beams.

_Dimensions._--Diameter of the outer shell 0.12, inner 0.06, outer pores 0.008, bars 0.004, inner pores 0.004.

_Habitat._--Cosmopolitan; Atlantic and Pacific, in various depths; fossil in Barbados and Sicily.

9. _Carposphæra modesta_, Haeckel.

_Haliomma modestum_, Stöhr, 1880, Palæontogr. Bd. xxvi. p. 86, Taf. i.
fig. 5.

Cortical shell thick walled, rough, three times as broad as the medullary shell, with regular circular pores of the same breadth as the bars. Eight to twelve pores on the quadrant. (Very common, like the preceding species, and connected with it by numerous intermediate forms.)

_Dimensions._--Diameter of the outer shell 0.12 to 0.2, inner 0.04 to 0.07, pores and bars 0.006 to 0.008.

_Habitat._--Atlantic and Pacific, from many Stations and at various depths; fossil in Barbados and Sicily.

10. _Carposphæra belladonna_, n. sp.

Cortical shell thick walled, smooth, five times as broad as the medullary shell, with regular circular pores of the same breadth as the bars. Twenty to twenty-two pores on the quadrant.

_Dimensions._--Diameter of the outer shell 0.3, inner 0.06, outer pores and bars 0.004.

_Habitat._--North Atlantic, Færöe Channel, John Murray.

11. _Carposphæra areca_, n. sp.

Cortical shell very thick walled, rough, twice as broad as the medullary shell, with regular circular pores half as broad as the bars. Eight to ten pores on the quadrant.

_Dimensions._--Diameter of the outer shell 0.12, inner 0.06, outer pores 0.03, bars 0.006.

_Habitat._--Indian Ocean, Ceylon, Haeckel, surface.

Subgenus 3. _Prunosphæra_, Haeckel, 1881, Prodromus, p. 451.

_Definition._--Pores of the cortical shell irregular polygonal, of unequal size or dissimilar form.

12. _Carposphæra prunulum_, n. sp.

Cortical shell thin walled, smooth, four times as broad as the medullary shell, with large irregular polygonal pores, four to eight times as broad as the bars. Connecting beams between them numerous.

{75}_Dimensions._--Diameter of the outer shell 0.24, inner 0.06, outer pores 0.008 to 0.016, bars 0.002.

_Habitat._--South Atlantic, Station 325, surface.

13. _Carposphæra corypha_, n. sp.

Cortical shell thin walled, rough, three times as broad as the medullary shell, with irregular polygonal pores, three to six times as broad as the bars. Connecting beams between the two shells twenty, regularly disposed.

_Dimensions._--Diameter of the outer shell 0.15, inner 0.05, outer pores 0.01 to 0.02, bars 0.003.

_Habitat._--South Pacific, Station 300, surface.

14. _Carposphæra borassus_, n. sp.

Cortical shell thick walled, smooth, three times as broad as the medullary shell, with irregular polygonal pores, two to four times as broad as the bars. Connecting beams between the two shells six, opposite by pairs in the three dimensive axes. (Similar to _Hexalonche aristarchi_, Pl. 22, fig. 3, but without external radial spines.)

_Dimensions._--Diameter of the outer shell 0.12, inner 0.04, outer pores 0.01 to 0.02, bars 0.005.

_Habitat._--Central Pacific, Station 268, surface.

Subgenus 4. _Phoenicosphæra_, Haeckel.

_Definition._--Pores of the cortical shell irregular roundish, of unequal size or form.

15. _Carposphæra nobilis_, Haeckel.

_Haliomma nobile_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 268; Abhandl., 1875, Taf. xxvii. fig. 6.

Cortical shell thin walled, rough, twice as broad as the medullary shell, with irregular roundish pores, two to four times as broad as the bars.

_Dimensions._--Diameter of the outer shell 0.1, inner 0.05, outer pores 0.01 to 0.02, bars 0.006.

_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, at various depths; fossil in Jurassic, Cretaceous, and Tertiary rocks.

16. _Carposphæra micrococcus_, n. sp.

Cortical shell thin walled, rough, seven times as broad as the medullary shell, with irregular roundish pores, three to six times as broad as the bars.

_Dimensions._--Diameter of the outer shell 0.2, inner 0.03, outer pores 0.012 to 0.025, bars 0.004.

_Habitat._--South Atlantic, Station 330, surface.

{76}17. _Carposphæra maxima_, n. sp.

Cortical shell thin walled, smooth, five times as broad as the medullary shell, with irregular roundish pores, of about the same breadth as the bars.

_Dimensions._--Diameter of the outer shell 0.4, inner 0.08, pores and bars 0.004 to 0.008.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

18. _Carposphæra nodosa_, n. sp. (Pl. 28, figs. 2, 2_a_).

_Anthomma nodosum_, Haeckel, 1879, Atlas, _loc. cit._

Cortical shell thick walled, covered with forty to fifty scattered pyramidal nodules, two and a half times as broad as the medullary shell, connected with it by very numerous thin radial beams. Outer and inner pores irregular roundish or polygonal, two to three times as broad as the bars. (This species in consequence of the cortical nodules may represent a peculiar genus, analogous to _Conosphæra_, called _Anthomma_.)

_Dimensions._--Diameter of the outer shell 0.13, inner 0.05, inner and outer pores 0.008 to 0.012, bars 0.004.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.

Genus 20. _Liosphæra_,[32] Haeckel, 1881, Prodromus, p. 449.

_Definition._--#Liosphærida# with two cortical (extracapsular) shells (without a medullary or intracapsular shell).

The genus _Liosphæra_ agrees with the preceding _Carposphæra_ in the possession of two concentric latticed spheres; but whilst in the latter genus the inner sphere is a medullary one (intracapsular), the outer a cortical shell (extracapsular), both connected by radial beams piercing the capsule-wall, here in _Liosphæra_ the central capsule lies freely within the inner lattice shell and is not pierced by radial beams. Therefore both shells are here cortical shells, both separated by a distance, which is constantly much smaller than the radius of the inner shell; whereas in _Carposphæra_ this distance is at least as large as that radius (commonly much larger). In _Carposphæra_ the number of pores in both shells is never the same; in several species of _Liosphæra_ this number is the same, each outer regular hexagonal pore exactly corresponding to an inner; the six corners of each connected by six short radial beams.

Subgenus 1. _Melitomma_, Haeckel.

_Definition._--Pores of both shells regular, in each shell all of nearly equal size and form.

1. _Liosphæra hexagonia_, n. sp. (Pl. 20, fig. 3).