Chapter XXXIII: Section IV: STICHOCYRTIDA, Haeckel, 1862, Monogr. d. Radiol., p. 280, 312 (8)

The family #Orosphærida# comprises those PHÆODARIA which possess a simple spherical or polyhedral lattice-shell, composed of hollow, very thick, non-articulate rods, without a peculiar shell-mouth. They agree in the considerable size of the spherical lattice-shell and the absence of a peculiar shell-mouth with the other #Phæosphæria#, but differ from them in the coarse and irregular shape of the massive network, which is composed of irregular polygonal meshes, separated by very thick concentrically stratified rods, containing a fine axial canal. The closely allied Sagosphærida differ from them in the delicate shape of the solid and very thin, filiform rods of the network, and its subregular {1591}triangular meshes. The Aulosphærida differ in the development of the peculiar nodal cavities and astral septa, by which the thin-walled cylindrical tubes of the articulated network are separated in the stellate nodal points. The Cannosphærida, closely allied to these latter, also differ in the articulated network, and further in the possession of an internal concentric shell. The Castanellida are sometimes similar to the Orosphærida, but distinguished by a peculiar large shell-mouth and a network of different shape.

The Orosphærida belong to the biggest Radiolaria, and the lattice-work of their spherical shell is of a ruder and coarser shape than in any of the other families of this class. Nevertheless they have been hitherto perfectly unknown, and were first discovered by the Challenger. We have been able to distinguish in the collection four genera and twenty-seven species. This strange fact may be explained by the circumstance, that they are in general rare, and restricted to a few localities, and that probably all the species are inhabitants of great depths. Complete shells also are rarely found, whilst broken fragments of their big shells, easily recognisable by the coarse irregular meshes and the thick stratified bars, are met with frequently in the Radiolarian ooze of some Pacific Stations, especially at Stations 265 and 268, at a depth of 2900 fathoms.

The lattice-shell of the Orosphærida is usually spherical, or an endospherical polyhedron (Pl. 106, fig. 4); rarely one axis is somewhat prolonged, so that the shell becomes slightly ellipsoidal (Pl. 106, fig. 1). Its diameter is usually between 2 and 3, often also between 2 and 1 mm., rarely more than 3, or less than 1 mm. The largest shells observed attained 5 to 6, the smallest 0.5 to 0.6 mm. Their general habit is very characteristic, so that they may be easily distinguished from all other spherical lattice-shells, especially from the Castanellida and from the simple Monosphærida (_Cenosphæra_, _Acanthosphæra_), with which I confounded them in the beginning (hence the first shell observed, figured in 1878, was placed among the Monosphærida in Pl. 12). A closer examination of the coarse network and of the peculiar structure of its thick bars always enables one to recognise even small isolated fragments of broken shells.

The meshes of the coarse network exhibit in all observed Orosphærida a very irregular form and unequal size; the majority are usually more or less quadrangular, more rarely they are triangular, pentagonal or hexagonal, very rarely rounded. They are often arranged in parallel rows, which seem to be determined by prominent crests, connecting the bases of the radial spines (Pl. 12, fig. 1; Pl. 106, fig. 4, &c.). The diameter of the meshes is usually between 0.05 and 0.1, often 0.1 to 0.2, rarely more than 0.25, or less than 0.025 mm. In _Oroplegma_, which develops an outer loose, spongy shell around the inner primary shell, the big meshes of the former become much larger and very irregular (Pl. 107, fig. 1).

The coarse bars which separate the large meshes of the irregular network are very thick and massive, cylindrical, usually of unequal thickness, straight or slightly curved, never angular or prismatic. Their diameter is usually between 0.01 and 0.02, rarely {1592}more than 0.03 or less than 0.005 mm. Their surface is either smooth or slightly spinulate. Examined in the dry state and by strong lenses, they constantly exhibit a fine, but distinct longitudinal striation, as the expression of concentric stratification. A fine axial canal or central tubule is usually visible in the axis of each rod, and often this axial canal is studded with numerous short lateral branches (Pl. 107, figs. 2, 4, 8). But very often the axial canals become rudimentary or lost, or are developed only in a part of the bars (Pl. 12, fig. 1). When they are completely developed, the entire network of the shell is drained by a reticulate system of communicating axial canals; they are probably filled by jelly in the living body. This tubular system never attains that regularity and high development which is constantly found in the Aulosphærida; and the characteristic stellate nodal points of the latter, with their astral septa, are never found in any of the Orosphærida. Moreover the wall of the tubular bars is very thin and structureless in the Aulosphærida, very thick and stratified in the Orosphærida, the enclosed canal very wide in the former, very narrow in the latter. The stratification of the concentric cylindrical lamellæ, which surround the narrow axial canal, is effected by the gradual deposition of the concentric layers, and is very similar to that which is found in the thick spicula of many sponges. The peculiar structure of the bars in the Orosphærida becomes very distinct if the skeleton be burned, or acted upon by fire for some time; it then assumes a brown colour and its surface often appears dimpled. Sometimes the concave dimples on the surface of the bars are rather deep and separated by prominent crests (Pl. 107, figs. 4, 7). The few genera of Orosphærida which are here distinguished have all the same structure, are closely allied, and differ mainly in the shape of the outer surface of the lattice-sphere. The latter is quite simple and smooth only in _Orona_. In the common _Orosphæra_ (Pl. 106, figs. 1-3) it is studded with radial spines. In the most frequent form, _Oroscena_, the shell has a pyramidal or tent-shaped elevation on the base of each radial spine, and usually the bases of the neighbouring spines are connected by strong prominent crests, the edges of the three-sided or four-sided pyramids (Pl. 12, fig. 1; Pl. 106, fig. 4). This remarkable form is more or less polyhedral, with concave sides, and is similar to the characteristic shells which are represented by _Auloscena_ among the Aulosphærida, by _Sagoscena_ and _Sagoplegma_ among the Sagosphærida (compare Pls. 108 and 110). The pyramids or tents, however, are in these latter more regularly and distinctly developed than in the Orosphærida. The radial spines which arise form the top of the pyramids are often branched, and the branches become connected to form an outer enveloping secondary shell or a loose spongy framework in _Oroplegma_ (Pl. 107, fig. 1).

The radial spines of the Orosphærida never exhibit a constant number or disposition in the individual species; their usual number is from twenty to sixty. Their form exhibits two different types, which, however, are not sharply separated; robust club-shaped and slender rod-shaped spines. The robust club-shaped spines are usually about as long as {1593}the diameter of the shell; they are longitudinally striped in the basal part, spinulate or reticulately dimpled in the distal part; sometimes they are straight, at other times curved or undulate (Pl. 106, figs. 1-4; Pl. 107, figs. 4-6). The slender rod-shaped spines are usually longer than the diameter of the shell, cylindrical, more or less curved or even undulate, smooth or thorny, sometimes irregularly branched, and often the branches are all or partly connected (Pl. 106, fig. 3; Pl. 107, fig. 1). In the majority of the shells observed the radial spines were found to be partly broken off. Their structure is the same as that of the bars of the network; but the central axial canal and the surrounding concentric lamellæ are usually more distinct than in the latter.

The central capsule of the Orosphærida lies in the centre of the spherical lattice-shell, surrounded by the voluminous calymma, which fills up its cavity. The form, structure, and size of the central capsule are the same as in the closely allied Aulosphærida (Pl. 111, fig. 2). Its diameter is usually about 0.2, or between 0.15 and 0.25, rarely more than 0.3 or less than 0.12. The dark phæodium is of about the same volume as the central capsule, and envelops its oral half with the radiate operculum and the proboscis of the astropyle. The two opposite parapylæ are small.

_Synopsis of the Genera of Orosphærida._

I. Subfamily { Surface smooth, without
Oronida. { radial spines, 671. _Orona_.
Surface of the shell {
without pyramidal { Surface studded with simple or
or tent-shaped { branched radial spines, 672. _Orosphæra_.
elevations. {

II. Subfamily { Pyramids of the surface free,
Oroscenida. { without spongy envelope, 673. _Oroscena_.
Surface of the shell {
with numerous { Pyramids of the surface
pyramidal or tent- { connected by a spongy
shaped elevations. { envelope or an external
{ lattice-shell, 674. _Oroplegma_.

Genus 671. _Orona_,[289] n. gen.

_Definition._--#Orosphærida# with a simple spherical or slightly ellipsoidal shell, without pyramidal elevations and radial spines.

The genus _Orona_ is the simplest of the Orosphærida, and probably the common ancestral form of this family. The lattice-shell is a simple fenestrated sphere, sometimes slightly ellipsoidal, with prolonged main axis, and bears on its surface neither tent-shaped elevations nor radial spines. It may be confounded with some big forms of _Cenosphæra_; it differs, however, in the possession of hollow central canals in the thick bars of the very coarse lattice-plate.

{1594}1. _Orona maxima_, n. sp. (Pl. 107, fig. 5).

Shell spherical, with very irregular polygonal meshes. Bars of the loose network smooth or slightly spinulate, very thick, with a pinnulate axial canal.

_Dimensions._--Diameter of the sphere 5.0 to 5.5, of the meshes 0.2 to 0.4, of the bars 0.01.

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

2. _Orona robusta_, n. sp.

Shell spherical, with irregular quadrangular meshes (intermingled with single triangular, pentagonal, and hexagonal meshes). Bars of the coarse network very thick, spinulate.

_Dimensions._--Diameter of the sphere 3.0 to 3.6, of the meshes 0.05, of the bars 0.012.

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

3. _Orona crassissima_, n. sp. (Pl. 107, fig. 7).

Shell ellipsoidal, slightly prolonged in the main axis, with irregular polygonal meshes of very different sizes and unequal forms. Bars of the coarse network very thick, thorny and dimpled, their surface being covered with a network of prominent polygonal crests.

_Dimensions._--Diameter of the sphere 3.0 to 4.0, of the meshes 0.2 to 0.5, of the bars 0.02 to 0.06.

_Habitat._--South Pacific, Station 289, depth 2550 fathoms.

Genus 672. _Orosphæra_,[290] n. gen.

_Definition._--#Orosphærida# with a simple, spherical (sometimes slightly ellipsoidal or polyhedral) lattice-shell without pyramidal elevations, but with numerous radial spines.

The genus _Orosphæra_ differs from the preceding _Orona_, its ancestral form, in the development of simple or branched radial spines. It bears, therefore, the same relation to the latter that _Acanthosphæra_ has to _Cenosphæra_. In the two latter genera, however, the bars of the network are solid, in the two former hollow. The species referred to _Orosphæra_ are closely allied and require a further accurate examination.

Subgenus 1. _Oronium_, Haeckel.

_Definition._--Radial spines simple, smooth or spiny, but neither branched nor arborescent.

{1595}1. _Orosphæra hastigera_, n. sp.

Radial spines cylindrical, straight, smooth, simple, about as long as the diameter of the spherical shell, and as broad as its smooth bars. Meshes of the network irregularly polygonal, the majority quadrangular, of different sizes.

_Dimensions._--Diameter of the sphere 1.0 to 1.2, length of the radial spines 1.1 to 1.5, middle breadth 0.004.

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

2. _Orosphæra spinigera_, n. sp.

Radial spines cylindrical, irregularly curved, thorny, simple, two to three times as long as the diameter of the spherical shell, and as broad as its spiny bars. Meshes of the network irregularly polygonal, the majority pentagonal.

_Dimensions._--Diameter of the sphere 1.5 to 1.8, length of the spines 3.0 to 5.0, breadth 0.006.

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

3. _Orosphæra fusigera_, n. sp.

Radial spines slender, spindle-shaped, straight, smooth, about as long as the diameter of the spherical or slightly ellipsoidal shell, in the thicker middle part five times as broad as the bars, and tapering equally towards both ends. Meshes of the network irregularly polygonal, the majority quadrangular, separated by smooth bars.

_Dimensions._--Diameter of the shell 1.0 to 1.2, length of the spines 1.2 to 1.6, basal breadth 0.02, middle breadth 0.1.

_Habitat._--North Pacific, Station 253, depth 3125 fathoms.

4. _Orosphæra foveolata_, n. sp.

Radial spines spindle-shaped, straight, dimpled, half as long as the radius of the spherical shell and three to five times as thick as the bars. Meshes irregular, polygonal, of very different shapes, separated by dimpled bars. (Similar to _Oroscena gegenbauri_, Pl. 106, fig. 4, but with spherical dimpled shell, without pyramidal elevations.)

_Dimensions._--Diameter of the shell 2.0 to 2.4, length of the spines 0.5, breadth 0.15.

_Habitat._--Central Pacific, Station 267, depth 2700 fathoms.

5. _Orosphæra serpentina_, n. sp. (Pl. 106, fig. 1).

Radial spines cylindrical, dimpled, undulate or curved in a snake-like manner, about as long as the diameter of the ellipsoidal or spherical shell and four to six times as broad as its smooth bars. Meshes very irregular, polygonal.

_Dimensions._--Diameter of the shell 1.0 to 1.2, length of the spines 0.12 to 0.15, breadth 0.12.

_Habitat._--South Pacific, Station 289, depth 2550 fathoms.

{1596}6. _Orosphæra horrida_, n. sp. (Pl. 106, fig. 2).

Radial spines club-shaped, very strong, straight, about as long as the diameter of the polyhedral shell, ovate and smooth in the distal half, slenderly conical, and armed with recurved spines in the proximal half; their outer third is the thickest, and five times as broad as the smooth bars of the coarse network. Meshes of the latter irregularly quadrangular.

_Dimensions._--Diameter of the shell 1.2 to 1.6, length of the spines 1.2 to 2.0, breadth 0.2.

_Habitat._--South Pacific, Station 291, depth 2250 fathoms.

7. _Orosphæra clavigera_, n. sp.

Radial spines club-shaped, thickened towards the distal end, more or less curved, spinulate, about as long as the diameter of the spherical shell; in the distal third four to six times as broad as the spinulate bars. Meshes irregularly polygonal, the majority pentagonal.

_Dimensions._--Diameter of the shell 2.0 to 2.5, length of the spines 1.8 to 2.2, breadth 0.16.

_Habitat._--Central Pacific, Station 263, depth 2650 fathoms.

Subgenus 2. _Orothamnus_, Haeckel.

_Definition._--Radial spines branched or arborescent.

8. _Orosphæra ramigera_, n. sp.

Radial spines cylindrical, spinulate, straight, about twice as long as the diameter of the spherical shell and as thick as its spinulate bars. Numerous simple spinulate branches, straight or slightly curved, and two to four times as long as the meshes, are irregularly scattered, and arise nearly perpendicularly from the bars.

_Dimensions._--Diameter of the shell 2.0 to 2.2, length of the spines 4 to 5, breadth 0.05.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

9. _Orosphæra furcata_, n. sp.

Radial spines cylindrical, smooth, irregularly curved, about as long as the radius of the spherical shell and as thick as its smooth bars, forked at the distal end, with two or three terminal branches of various lengths. Meshes irregularly polygonal (the majority hexagonal).

_Dimensions._--Diameter of the shell 1.2, length of the spines 0.7, breadth 0.03.

_Habitat._--Indian Ocean, Madagascar (Rabbe), surface (?).

10. _Orosphæra confluens_, n. sp.

Radial spines cylindrical, smooth, irregularly curved, two to three times as long as the diameter of the polyhedral shell, twice as broad as its smooth bars, bearing numerous irregular, lateral {1597}branches, which are partly confluent and fenestrated (similarly as in Pl. 107, fig. 1), but not forming an outer lattice-shell. Meshes irregularly polygonal.

_Dimensions._--Diameter of the shell 3.3, length of the spines 6 to 9, breadth 0.03.

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

11. _Orosphæra arborescens_, n. sp. (Pl. 106, fig. 3).

_Orothamnus arborescens_, Haeckel, 1881, Atlas, loc. cit.

Radial spines cylindrical, rough, more or less curved, somewhat longer than the diameter of the subspherical or slightly ellipsoidal shell, and at the thicker base three times as broad as its smooth bars, bearing numerous irregularly branched and curved, sometimes confluent, lateral branches. Meshes irregularly quadrangular.

_Dimensions._--Diameter of the shell 1.2 to 1.6, length of the spines 1.5 to 2.2, breadth 0.06.

_Habitat._--South Atlantic, Station 335, depth 1425 fathoms.

Genus 673. _Oroscena_,[291] n. gen.

_Definition._--#Orosphærida# with a simple, polyhedral or subspherical lattice-shell, and with numerous pyramidal elevations on its surface, the top of which bears a radial spine.

The genus _Oroscena_ differs from the preceding _Orosphæra_ in the possession of numerous pyramidal or tent-shaped elevations, each of which bears on its top a radial spine. It exhibits therefore the same relation to the latter that _Sagoscena_ does to _Sagosphæra_ and _Auloscena_ to _Aulosphæra_. The bases of the radial spines are usually connected by prominent concave crests, the edges of the pyramids. The species described of _Oroscena_ seem to be very variable and transformistic.

Subgenus 1. _Oroscenium_, Haeckel.

_Definition._--Radial spines simple, smooth or spiny, but neither branched nor forked.

1. _Oroscena gegenbauri_, n. sp. (Pl. 106, fig. 4).

Radial spines club-shaped, about half as long as the radius of the shell, cylindrical and finely sulcate in the basal third, ovate and elegantly dimpled in the distal two-thirds. The bases of the radial spines are connected by prominent concave crests, which form the edges of the polyhedral shell. Meshes irregularly polygonal, the majority quadrangular, separated by denticulate bars.

{1598}_Dimensions._--Diameter of the shell (without spines) 1.2 to 1.8, of the meshes 0.04 to 0.1; length of the spines 0.3 to 0.5.

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

2. _Oroscena mülleri_, n. sp. (Pl. 107, fig. 8).[292]

Radial spines club-shaped, very similar to that of the preceding species, but much larger, about as long as the radius of the shell. Meshes irregularly polygonal, the majority pentagonal, separated by smooth bars.

_Dimensions._--Diameter of the shell 2.0 to 2.4, length of the spines 1.0 to 1.2.

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

3. _Oroscena cuvieri_, n. sp. (Pl. 107, fig. 6).

Radial spines club-shaped, compressed and smooth in the proximal half, spindle-shaped and dimpled in the distal half, about as long as the radius of the shell. Meshes irregularly polygonal, the majority hexagonal, separated by denticulate bars.

_Dimensions._--Diameter of the shell 1.5, length of the spines 0.8.

_Habitat._--South Pacific, Station 289, depth 2550 fathoms.

4. _Oroscena bærii_, n. sp. (Pl. 107, fig. 4).

Radial spines nearly spindle-shaped, undulate, tapering from the thicker middle towards both ends, coarsely dimpled, about one-third as long as the radius of the shell. Meshes irregularly polygonal, the majority pentagonal, separated by spinulate bars.

_Dimensions._--Diameter of the shell 3.2, length of the spines 1.0 to 1.2, breadth 0.1.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.

5. _Oroscena wolffii_, n. sp.

Radial spines cylindrical, spinulate, more or less curved, longer than the diameter of the shell and about twice as broad as its bars. Meshes irregularly polygonal, of very variable form and unequal size, separated by smooth bars.

_Dimensions._--Diameter of the shell 2.5, length of the spines 3.0 to 3.5, breadth 0.02.

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

Subgenus 2. _Orodendrum_, Haeckel.

_Definition._--Radial spines branched or arborescent.

{1599}6. _Oroscena huxleyi_, n. sp. (Pl. 12, figs. 1, 1_a_).

Radial spines cylindrical, obliquely ascending and irregularly curved, about as long as the diameter of the shell and somewhat thicker than its thorny bars. A variable number of short, irregular, partly simple, partly forked, lateral branches arises from the spines. Meshes of the network very irregular, partly solid, partly hollow (fig. 1_a_*), the majority quadrangular. This species, the first observed form of Orosphærida (captured the 21st February 1873 at Station 5), was at the beginning of my observations, in 1876, and when I had no knowledge of the central capsule, erroneously regarded by me as a gigantic Sphæroid (of the Monosphærida) and therefore placed in Pl. 12. The long branched spines, afterwards observed complete in another specimen, were broken off in the specimen first figured.

_Dimensions._--Diameter of the shell 2.0 to 2.5, length of the spines 2 to 3 mm., breadth 0.03.

_Habitat._--North Atlantic (west of Canary Islands), Station 5, depth 2740 fathoms.

7. _Oroscena darwinii_, n. sp.

Radial spines cylindrical, irregularly curved and branched, about twice as long as the diameter of the shell; the branches are all again ramified and partly confluent (as in Pl. 107, fig. 1). The branches and the bars of the network are of equal breadth, smooth (not thorny as in the similar preceding species). Meshes rather subregular, quadrangular.

_Dimensions._--Diameter of the shell 2.4 to 2.8, length of the spines 4 to 5 mm., breadth 0.015.

_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms.

8. _Oroscena duncanii_, n. sp.

? _Hexactinellida dictyonina_, Martin Duncan, 1881, Journ. Roy. Micr.
Soc., p. 175, pl. iii. figs. 4, 6.

Radial spines cylindrical, thorny, arborescent, somewhat shorter than the diameter of the shell, with irregular ramified branches (similar to _Orosphæra arborescens_, Pl. 106, fig. 3). The size and ramification of the arborescent spinulate branches decrease towards the apex. The thicker branches are from two to three times as broad as the spinulate bars of the network. Meshes of the latter irregular, the majority quadrangular.

_Dimensions._--Diameter of the shell 3.2, length of the spines 3.5 to 4.5, breadth 0.02 to 0.3.

_Habitat._--South Atlantic, Station 318, depth 2040 fathoms; coast of Portugal, 1095 fathoms.

Genus 674. _Oroplegma_,[293] n. gen.

_Definition._--#Orosphærida# with a spongy, spherical or slightly polyhedral lattice-shell, which is enveloped by a loose spongy framework and bears numerous radial spines.

The genus _Oroplegma_ differs from the other Orosphærida in the development of an external lattice-work enveloping the internal primary shell, and produced by the union {1600}of the branches of the radial spines. This outer shell is either a simple lattice-plate (comparable to the cortical shell of _Diplosphæra_), or a spongy framework (as in _Rhizoplegma_).

Subgenus 1. _Oroplegmium_, Haeckel.

_Definition._--External shell a simple fenestrated lamella, forming an outer concentric lattice-sphere around the inner primary shell.

1. _Oroplegma diplosphæra_, n. sp. (Pl. 107, fig. 1).

Radial spines slender, cylindrical, smooth, more or less curved, about twice as broad as the smooth bars of the network. External shell a simple irregular lattice-sphere, with loose polygonal meshes, which are on an average three to four times as broad as the irregular meshes of the internal shell. The free prominent parts of the radial spines are irregularly branched, very long, with partly confluent branches.

_Dimensions._--Diameter of the inner sphere 1.5 to 2.0, of the outer 2.5 to 3.0; length of the free spines 1.2, breadth 0.04.

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

2. _Oroplegma spinulosum_, n. sp.

Radial spines slender, cylindrical, thorny, more or less curved, very similar to those of the preceding species; the shell also much resembles that of _Oroplegma perplexum_. It differs from the latter in the more regular fenestration of both shells, and mainly in the shape of the bars and the spine-branches, which are all spinulate and densely studded with small conical thorns.

_Dimensions._--Diameter of the inner sphere 1.5 to 2.0, of the outer 2.5 to 3.0; length of the spines 1.2, breadth 0.03.

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

3. _Oroplegma velatum_, n. sp.

Radial spines stout, cylindrical, somewhat club-shaped, spiny, slightly curved, about three to four times as broad as the thorny bars of the network. External shell a simple lattice-sphere with irregular polygonal meshes, which are for the most part pentagonal and about four times as broad as the polygonal meshes of the inner shell. The free prominent parts of the radial spines are thickened, club-shaped, and about as long as the radius.

_Dimensions._--Diameter of the inner sphere 2.0 to 2.4, of the outer 2.8 to 3.6; length of the free spines 0.5 to 0.7, breadth 0.12 to 0.15.

_Habitat._--Tropical Atlantic, Station 338, depth 1990 fathoms.

{1601}Subgenus 2. _Orodictyum_, Haeckel.

_Definition._--External shell a complex framework, forming an outer spongy envelope around the inner primary shell.

4. _Oroplegma spongiosum_, n. sp. (Pl. 107, fig. 3).

Radial spines stout, cylindrical, spinulate, slightly curved, three to five times as broad as the inner rough bars. External shell with pyramidal elevations, forming a loose spongy framework, the irregular polygonal meshes of which are two to five times as broad as those of the enclosed internal shell; the thickness of the spongy envelope equals about half the radius of the inner shell. External free prolongations of the radial spines about equal to the radius.

_Dimensions._--Diameter of the inner sphere 2 to 2.5, of the outer 3 to 3.5; length of the free radial spines 0.5 to 2.0, breadth 0.1.

_Habitat._--North Pacific, Station 241, depth 2300 fathoms.

5. _Oroplegma giganteum_, n. sp. (Pl. 107, fig. 2).

Radial spines slender, cylindrical, spinulate, irregularly curved, about twice as broad as the spinulate tubular bars of the network (fig. 2). External shell an irregular, loose, spongy framework, the polygonal meshes of which are three to six times as broad as the rounded irregular meshes of the inner shell; the thickness of the spongy envelope about equals the radius of the inner shell. External free prolongation of the radial spines irregularly branched.

_Dimensions._--Diameter of the inner sphere 3.2 to 3.5, of the outer 5.4 to 6.6; length of the free spines 1.4 to 1.5, breadth 0.03.

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

Family LXXV. #SAGOSPHÆRIDA#, n. fam. (Pl. 108).

_Definition._--PHÆODARIA with a large spherical (or sometimes polyhedral), very delicate shell, which is composed of solid, very thin and long threads. Nodal points of the arachnoidal network without astral septa. Meshes large, triangular. Surface of the shell usually armed with radial spines and often studded with pyramidal elevations. No peculiar mouth in the shell. Central capsule tripylean, in the centre of the shell.

The family #Sagosphærida# comprises a rather large number of common and widely distributed PHÆODARIA, which in respect of the special form and differentiation of the shell exhibit the greatest similarity to the common Aulosphærida, but differ essentially from them in the peculiar structure of the network. This is not composed of stout hollow cylindrical tubes, but of solid, very thin threads; and these fine arachnoidal {1602}threads are simply united or confluent at the nodal points, and are not connected by a radial or stellate septal junction, as in the Aulosphærida. There are, therefore, neither astral septa nor a nodal cavity in each nodal point. The delicate shape of the thin and fragile threads separates the Sagosphærida from the closely allied Orosphærida, the thick bars of which contain a central axial canal and exhibit a concentric structure. Another difference between these two similar families is indicated by the form of the meshes of the network, which are constantly triangular in the Sagosphærida, but irregularly polygonal or quadrangular in the Orosphærida. The general habit of these two families, however, is very different, since the big and stout spheres of the Orosphærida are the coarsest and rudest spherical shells of all Radiolaria, whilst the fragile and delicate spheres of the Sagosphærida represent the finest and most tender in the whole class.

The spherical lattice-shell of the Sagosphærida has a considerable size, its diameter being usually between one and three millimetres, rarely less or more. Some species are very common and widely distributed, usually accompanying the common Aulosphærida; very frequently the similar shells of the two are found interwoven. But in spite of this frequency and visible size, the Sagosphærida have hitherto almost completely escaped the attention of observers. The main cause of this strange fact may be their extreme delicacy and fragibility, so that complete and intact shells occur very rarely, the majority being more or less broken and incomplete. It seems that only two species of Sagosphærida have been hitherto observed.

The first form described is _Sagmarium trigonizon_, observed by me in 1859 living at Messina, and figured in 1862 in my Monograph as _Dictyosoma trigonizon_ (Taf. xxvi. figs. 4-6), but afterwards called _Spongodictyum trigonizon_ (_loc. cit._, p. 459). I supposed at that time (now twenty-five years ago), that this remarkable and in many respects distinct form might belong to the Spongosphærida, and that an internal, triple, spherical lattice-shell, found entangled in its spongy framework, might be its central "medullary shell." But at present, having found many shells of different Radiolaria accidentally entangled in the arachnoidal framework of various Sagosphærida, I think it much more probable, that that "triple medullary shell," composed of three simple concentric lattice-spheres, was really a species of _Plegmosphæra_ or _Actinomma_, accidentally entangled in the arachnoidal spongy framework of _Sagmarium_. This is the more probable, as I had observed very frequently at Messina, in 1859, fragments of that framework, but only once the triple lattice-shell which I supposed to be the "triple medullary shell" of the former. The peculiar structure of the loose framework, its very large triangular meshes and thin arachnoidal bars, partly provided with cruciate verticils (_loc. cit._, Taf. xxvi. figs. 4, 5) have been very frequently observed by me during the last ten years in various Sagosphærida (PHÆODARIA), but never in any true #Sphæroidea# (SPUMELLARIA).

The second species of Sagosphærida hitherto observed, is _Sagoscena gracilis_, described and figured in 1879 by Richard Hertwig as _Aulosphæra gracilis_ (Organism. {1603}d. Radiol., p. 91, Taf. ix. fig. 4). He too observed only fragments of destroyed and incomplete shells, and was led by their striking similarity to fragments of _Aulosphæra elegantissima_ to unite it with the genus _Aulosphæra_. But the accurate description and the figure given by him of the fragments observed leaves no doubt that it was a true _Sagoscena_.

In the collection of the Challenger the Sagosphærida are so common and so richly represented, that we may describe here not less than seven genera and thirty-three species, but this may be a small part only of the numerous species of this family, which seems to be widely distributed over all oceans, in the Arctic and Antarctic as well as in temperate and tropical zones. The majority are inhabitants of the surface, but a few species have been found only in deep-sea soundings. A striking fact is their usual association with the similar Aulosphærida. The majority of shells of both families were found entangled in one another.

The shell of all Sagosphærida seems to be spherical or nearly spherical in the complete state; but complete spheres can be observed only very rarely, and it is not impossible that deviations from the spherical form exist just as in some Aulosphærida (_e.g._, the lenticular _Aulophacus_ and the spindle-shaped _Aulatractus_). The diameter of the spheres usually seems to be between 1 and 2, often also 3 millimetres; very rarely shells occur which are less than 1 or more than 3 (4 or 5) millimetres.

The siliceous network or lattice-work of the Sagosphærida exhibits a very characteristic shape, and this enables one to distinguish it at first sight from all the other Radiolaria. It is constantly composed of triangular, very large meshes, which are separated by very thin and delicate, flexible and elastic bars. With respect to the arrangement of these meshes we distinguish two different subfamilies; in the Sagenida the wall of the spherical shell is very thin and composed only of a simple lattice-plate; in the Sagmarida the wall is thickened and spongy, with a complete wicker-work of threads, interwoven in different directions.

The typical triangular form of the large meshes is usually regular or subregular in the fenestrated Sagenida, more or less irregular in the spongy Sagmarida. In many cases, however, irregular triangles also occur in the former, and regular triangles in the latter subfamily. Very rarely irregular polygonal meshes are found in a part of the network, small connecting bars being developed accidentally between two neighbouring sides of the triangles. The diameter of the meshes is usually between 0.1 and 0.2 mm., often also greater, between 0.2 and 0.3, rarely smaller, 0.05 to 0.09 mm. The triangular meshes of the Sagosphærida are therefore on an average ten times as large as the usual meshes in the network of the common #Sphæroidea#.

The filiform bars, or the thread-shaped, very long and thin rods between the triangular meshes, are scarcely less characteristic of the Sagosphærida than the form and size of the meshes. Their length is usually between 0.1 and 0.2 mm., often also {1604}from 0.2 to 0.3 mm., whilst their thickness is only 0.002 to 0.004 mm., often it is less than 0.001, rarely more than 0.005 mm. The nodal points of the network, in which six threads are usually united, are more or less thickened, often stellate (Pl. 108, figs. 9, 12, &c.). Sometimes they are pierced by a central pore. The thin threads are constantly cylindrical, never edged or prismatic, very elastic and flexible; usually they are perfectly smooth, rarely spiny or thorny, sometimes provided with scattered cruciate verticils of lateral branches, as in _Sagena crucifera_ and in the first described form of this family, _Sagmarium trigonizon_ (compare my Monograph, 1862, Taf. xxvi. fig. 5).

The surface of the spherical shell is smooth only in two genera of Sagosphærida, in _Sagena_ and _Sagmarium_ (Pl. 108, figs. 2, 8). In the five other genera it is covered either with radial spines, arising from the nodal points of the network, or with peculiar cortical pyramids or tent-shaped elevations (Pl. 108, figs. 1, 3-6, &c.). These pyramids are of the same characteristic shape as in the similar _Auloscena_ among the Aulosphærida (Pl. 110, fig. 1); usually, however, they are less regular than in the latter. The pyramids or tents are usually six-sided, often, however, they are also four-sided or three-sided, more rarely five, seven or more sided. The edges of the pyramids are formed by filiform bars similar to those which compose the original lattice-work of the Sagosphærida. The cavity of the pyramids is quite simple in _Sagoscena_ (figs. 1, 5, 6), whilst in _Sagenoscena_ and _Sagoplegma_ a radial column arises in its axis, the thickened axial rod (figs. 3, 4, 10).

The radial spines, which arise either from the tops of the pyramids or from the nodal points of the network, exhibit in the Sagosphærida a variety and elegance similar to the closely allied Aulosphærida. Sometimes a single radial spine arises in each nodal point or at the top of each pyramid (figs. 3, 4, 10); at other times two, three, or four (rarely more) divergent spines (figs. 6-9, 12, 13). These are rarely quite simple, usually provided with lateral and terminal branches. The lateral branches are either scattered irregularly, or regularly disposed in elegant verticils, each of which is usually composed of three or four short branches (Pl. 108, figs. 9, 13). The terminal branches form either a similar verticil, or a bunch or corona, composed of numerous radial secondary spines. The distal ends of the terminal as well as of the lateral branches are rarely simple, usually they are provided with a spinulate knob or with an elegant spathilla (Pl. 108, figs. 3, 9, 13).

The _central capsule_ of the Sagosphærida is comparatively small, as it also is in the Aulosphærida and Orosphærida. Its diameter is usually about one-third or one-fourth that of the enveloping shell, between 0.2 and 0.3, often only 0.12 to 0.18, rarely more than 0.3 mm. It is surrounded on the oral half by a red or dark phæodium and separated from the inner surface of the shell by the voluminous calymma. The subspherical nucleus is usually about half as broad as the capsule. The three openings of the latter, the large tubular astropyle and the two opposite lateral parapylæ, exhibit the same shape {1605}as in the closely allied Aulosphærida (Pl. 111, fig. 3). The pseudopodia arising from the central capsule form a loose network in the calymma, and proceed over its surface as numerous delicate radial filaments, often supported by the radial spines.

_Synopsis of the Genera of Sagosphærida._

-------------------------------------------------------------------------
I. Subfamily Sagenida.
Wall of the spherical shell composed of a simple lattice-plate with
or without pyramidal elevations.
-------------------------------------------------------------------------
{ No radial spines, surface
Surface of the spherical { smooth, 675. _Sagena_.
shell smooth or spiny, {
without pyramidal { Radial spines in the nodal
elevations. { points, 676. _Sagosphæra_.

Surface of the spherical { Pyramids without internal
shell covered with { axial rod, 677. _Sagoscena_.
pyramidal or tent- {
shaped elevations. { Pyramids with an internal
{ radial axial rod, 678. _Sagenoscena_.
-------------------------------------------------------------------------
II. Subfamily Sagmarida.
Wall of the spherical shell spongy, composed of an irregular
complicated wicker-work.
-------------------------------------------------------------------------
Surface of the spherical { Surface smooth, without
shell smooth or spiny, { radial spines, 679. _Sagmarium_.
without pyramidal {
elevations. { Surface studded with
{ radial spines, 680. _Sagmidium_.

Surface of the spherical { Pyramids on the top with a
shell covered with { radial spine or a bunch
pyramidal elevations. { of divergent spines, 681. _Sagoplegma_.

Subfamily 1. SAGENIDA, Haeckel.

_Definition._--#Sagosphærida# with a delicate spherical shell, the thin wall of which is composed of a simple lattice-plate, not spongy.

Genus 675. _Sagena_,[294] n. gen.

_Definition._.--#Sagosphærida# with a delicate shell, the thin wall of which is composed of a simple smooth lattice-plate, without radial spines.

The genus _Sagena_ is the simplest of the Sagosphærida and may be regarded as the common ancestral form of this family. The delicate wall of the simple spherical lattice-shell is composed of large, regular, or subregular, triangular meshes, the nodal points of which bear no radial spines. It agrees therefore perfectly with _Aularia_, and differs from this simplest form of Aulosphærida only in the structure of the skeleton, which is composed not of hollow articulated tubes, but of very thin solid threads. The skeleton may therefore also be confounded with _Cenosphæra_, but the central capsule of this latter is "peripylean," with numerous fine pores in the entire wall, whilst that of _Sagena_ is "tripylean," having the proboscis of all PHÆODARIA.

{1606}1. _Sagena ternaria_, n. sp. (Pl. 108, fig. 8).

Network subregular, with equilateral triangular meshes, intermingled with single irregular meshes (fig. 8). Bars of the network smooth, its nodal points solid, not pierced.

_Dimensions._--Diameter of the spherical shell 1.5 to 2.5, length of the bars 0.1 to 0.2, breadth 0.002 to 0.005.

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

2. _Sagena pertusa_, n. sp.

Network subregular, with nearly equal triangular meshes. Bars of the network smooth, its nodal points pierced by a circular hole.

_Dimensions._--Diameter of the shell 1.2 to 1.8, length of the bars 0.2 to 0.25, breadth 0.003.

_Habitat._--Central Pacific, Stations 270 to 274, surface.

3. _Sagena triangula_, n. sp.

Network very regular, with equilateral triangular meshes. Bars of the network spinulate, like those of _Sagoplegma spinulosa_. (Pl. 108, fig. 14), its nodal points solid, not pierced.

_Dimensions._--Diameter of the shell 2.2, length of the bars 0.25, breadth 0.004.

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

4. _Sagena crucifera_, n. sp.

Network more or less irregular, with unequal triangular meshes. Bars of the network studded with scattered, rectangular, minute crosses, arising perpendicularly, each cross composed of four small equal bars. Nodal points partly solid, partly pierced by a hole. Network very similar to that of _Dictyosoma trigonizon_, figured in my Monograph, Taf. xxvi. figs. 4, 5.

_Dimensions._--Diameter of the shell 1.5, length of the bars 0.1 to 0.2, breadth 0.003.

_Habitat._--Mediterranean, Atlantic, Canary Islands, Station 353, surface.

Genus 676. _Sagosphæra_,[295] n. gen.

_Definition._--#Sagosphærida# with a delicate spherical shell, the thin wall of which is composed of a simple lattice-plate, and bears on its nodal points radial spines.

The genus _Sagosphæra_ differs from the preceding _Sagena_, its ancestral form, in the development of radial spines on the nodal points of the simple delicate lattice-sphere. It exhibits therefore the same relation to the latter as _Aulosphæra_ bears to _Aularia_. {1607}The regular or subregular triangular meshes of the lattice-sphere are separated in _Sagosphæra_ by solid, very thin threads, in the similar _Aulosphæra_, however, by thicker hollow tubes. The genus _Sagosphæra_ may be divided into two subgenera:--_Sagosphærella_ with a single radial spine at each nodal point of the network, and _Sagosphæroma_ with a bunch of two to four or more divergent radial spines.

1. _Sagosphæra trigonilla_, n. sp.

Radial spines simple, straight, smooth, about as long as the smooth bars of the network, a single one at each nodal point. Meshes very regular, of equal size, equilateral triangular. (Similar to the common _Aulosphæra trigonopa_.)

_Dimensions._--Diameter of the sphere 1.2 to 1.8, length of the bars 0.1 to 0.2, breadth 0.002 to 0.006.

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

2. _Sagosphæra penicilla_, n. sp. (Pl. 108, fig. 10).

Radial spines straight, stout, a single one at each nodal point, twice as thick, but of the same length as the smooth bars of the network, armed at the distal end with a brush of numerous thin radial bristles. (Very similar to _Sagenoscena penicillata_, but without pyramidal elevations on the surface of the sphere.)

_Dimensions._--Diameter of the sphere 1.0 to 1.5, length of the bars 0.1 to 0.15, breadth 0.002 to 0.004.

_Habitat._--Antarctic Ocean, Station 154, surface.

3. _Sagosphæra verticilla_, n. sp.

Radial spines slender, slightly curved, a single one at each nodal point, armed with three to five cruciate verticils, each of which is composed of four crossed lateral branches with spinulate terminal knobs (similar to _Sagmidium crucicorne_, Pl. 108, fig. 9), but with a spherical shell, having a simply latticed, and not a spongy wall.

_Dimensions._--Diameter of the sphere 2.0 to 2.5, length of the bars 0.1 to 0.2, breadth 0.002.

_Habitat._--North Pacific, Station 256, surface

4. _Sagosphæra furcilla_, n. sp. (Pl. 108, figs. 11, 11_a_).

Radial spines short, spinulate, with a spiny terminal knob (fig. 11_a_), two or three arising from each nodal point of the network in divergent directions, only one-third or one-fourth as long as its smooth bars. Meshes more or less irregular, triangular.

_Dimensions._--Diameter of the sphere 2.2, length of the bars 0.2 to 0.3, breadth 0.004.

_Habitat._--South Pacific, Station 293, depth 2025 fathoms.

{1608}5. _Sagosphæra coronilla_, n. sp.

Radial spines slender, smooth, three to six arising from each nodal point of the network in divergent directions, about as long as its smooth bars, crowned at the distal end with a bunch of twenty to thirty radial terminal branches, and provided with a spinulate knob at the distal end (similar to _Sagenoscena stellata_, Pl. 108, fig. 3).

_Dimensions._--Diameter of the sphere 3.0, length of the bars 0.1 to 0.2, breadth 0.002.

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

Genus 677. _Sagoscena_,[296] n. gen.

_Definition._--#Sagosphærida# with a delicate spherical shell, the thin wall of which is composed of a simple lattice-plate and covered with numerous pyramidal elevations; each pyramid bears on its top one or more radial spines, but has no axial rod in its radial axis.

The genus _Sagoscena_, and the following closely allied _Sagenoscena_ (both very common and widely distributed), exhibit a peculiar and very remarkable structure of the delicate lattice-shell, similar to that which _Auloscena_ represents among the Aulosphærida. The surface of the simple spherical lattice-shell is covered with numerous pyramidal or tent-shaped elevations. These elegant and delicate pyramids are, however, in _Sagoscena_ usually not so regular as in the similar _Auloscena_; the edges of the pyramids are in the latter hollow cylindrical tubes, in the former thin solid threads. The top of each pyramid usually bears a bunch of apical spines.

1. _Sagoscena castra_, n. sp. (Pl. 108, fig. 1).

Pyramids subregular, of equal size and similar form, usually three-sided, crowned at the top with three divergent apical spines, which alternate with the three edges of the pyramids and bear a small spinulate terminal knob. (Some four-sided and single five-sided pyramids are often intermingled with the three-sided.)

_Dimensions._--Diameter of the sphere 1.7 to 2.3, length of the bars 0.2 to 0.25, breadth 0.008.

_Habitat._--South-Eastern Pacific, Stations 295, 296, surface.

2. _Sagoscena tentorium_, n. sp. (Pl. 108, fig. 6).

Pyramids subregular, of equal size and similar form, usually four-sided, crowned at the top with three divergent apical spines, which are trifurcate at the distal end. (Some three-sided and five-sided pyramids are often intermingled with the four-sided.)

_Dimensions._--Diameter of the sphere 2.2, length of the bars 0.2 to 0.25, breadth 0.005.

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

{1609}3. _Sagoscena prætorium_, n. sp. (Pl. 108, fig. 7).

Pyramids subregular, of equal size and similar form, usually four-sided, crowned at the distal top with three or four divergent apical spines, which bear some irregular verticils of lateral and terminal branches. (Some five-sided and some six-sided pyramids are often intermingled with the four-sided.)

_Dimensions._--Diameter of the sphere 2.6, length of the bars 0.3, breadth 0.006.

_Habitat._--Central Pacific, Stations 271 to 274, surface.

4. _Sagoscena pellorium_, n. sp. (Pl. 108, fig. 5).

Pyramids subregular, of equal size and similar form, usually five-sided or six-sided, crowned at the distal end with three to six divergent apical spines, which bear an irregularly spinulate terminal knob. (The size and form of the apical spines is here very variable, as well as the number of the edges of the pyramids, which varies between three and six.)

_Dimensions._--Diameter of the sphere 3.2, length of the bars 0.15 to 0.25, breadth 0.008.

_Habitat._--Antarctic Ocean, Station 156, surface.

5. _Sagoscena cruciarium_, n. sp.

Pyramids subregular, usually six-sided (intermingled with single five-sided and seven-sided or eight-sided forms), crowned at the distal top with three divergent, slender, apical spines, each of which bears three to six regular cruciate verticils; the four crossed lateral branches of each verticil bearing a spinulate terminal knob. (Similar to _Sagoplegma scenophora_, Pl. 108, fig. 13.)

_Dimensions._--Diameter of the shell 2.5, length of the bars 0.2 to 0.3, breadth 0.004.

_Habitat._--North Pacific, Stations 240 to 244, surface.

6. _Sagoscena debilis_, n. sp.

Pyramids more or less irregular, with four, five, or six sides, of somewhat different form and unequal size; crowned at the top with one, two, or three slender apical spines, of variable length. These spines as well as the bars of the network bear scattered cruciate verticils, each usually composed of four crossed, small, lateral branches.

_Dimensions._--Diameter of the shell 2 to 3.0, length of the bars 0.1 to 0.15, breadth 0.003.

_Habitat._--Central Pacific, Stations 263 to 274, surface.

7. _Sagoscena gracilis_, Haeckel.

_Aulosphæra gracilis_, R. Hertwig, 1879, Organism. d. Radiol., p. 91,
Taf. ix. fig. 4.

Pyramids more or less irregular, with five, six, or seven sides, often of somewhat different form and unequal size; crowned at the top with a single radial spine, which has the same size as the {1610}bars of the network, and bears in its distal half four cruciate verticils, each composed of four crossed and curved horizontal branches.

_Dimensions._--Diameter of the sphere 1 to 2, length of the bars 0.08 to 0.09, breadth 0.002.

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

8. _Sagoscena fragilis_, n. sp.

Pyramids very irregular, with four to eight sides, of different form and unequal size; crowned at the top with a single, slender, radial spine, of the same thickness as the slender bars of the network; the latter as well as the former are smooth, without lateral branches.

_Dimensions._--Diameter of the sphere 1.0 to 2.0, length of the bars 0.1 to 0.2, breadth 0.001 to 0.002.

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

Genus 678. _Sagenoscena_,[297] n. gen.

_Definition._--#Sagosphærida# with a delicate spherical shell, the thin wall of which is composed of a simple lattice-plate and covered with numerous pyramidal elevations; each pyramid bears on its top one or more radial spines, and has an internal axial rod in its radial axis.

The genus _Sagenoscena_ differs from the preceding closely allied _Sagoscena_ in the possession of an internal radial axial rod, which arises in the centre of the base of each pyramid, and is prolonged usually over its apex into a free, radial, apical spine. The distal end of the latter is usually armed with a bunch of terminal teeth or bristles. In the similar _Sagoscena_ the internal cavity of the pyramids is simple, without axial rod.

1. _Sagenoscena stellata_, n. sp. (Pl. 108, fig. 3).

Pyramids rather regular, usually six-sided (intermingled with single five-sided and four-sided forms); their axial rod and its prolongation, the radial apical spine, three to four times as thick as the slender edges of the pyramid. The distal end of the apical spine bears an elegant star of numerous radially divergent terminal branches, each of which is armed with a spinulate terminal knob.

_Dimensions._--Diameter of the sphere 3.5 to 4.0, length of the net bars 0.3, breadth 0.003; length of the radial spines 0.2, breadth 0.012.

_Habitat._--South Atlantic, Station 318, depth 2040 fathoms.

2. _Sagenoscena ornata_, n. sp. (Pl. 108, fig. 4).

Pyramids rather regular, usually six-sided (intermingled with single five-sided and seven-sided forms); their axial rod and apical spine spindle-shaped, two to four times as thick as the smooth bars {1611}of the network. The distal end of the radial spines bears an elegant, foliate, terminal knob, composed of four to six vertical pinnate leaves, lying in crossed meridional planes.

_Dimensions._--Diameter of the sphere 2 to 3, length of the rods 0.1 to 0.2, breadth 0.003 to 0.01.

_Habitat._--Antarctic Ocean, Station 156, depth 1975 fathoms.

3. _Sagenoscena penicillata_, n. sp. (Pl. 108, fig. 10).

Pyramids rather regular, usually six-sided (intermingled with single five-sided, seven-sided, and eight-sided forms); their axial rod and apical spine spindle-shaped, thicker than the smooth bars of the network. The distal end of the radial spines is penicillate and bears a brush of bristle-shaped, radial, terminal spinules (compare _Sagosphæra penicilla_, p. 1607).

_Dimensions._--Diameter of the sphere 1 to 1.5, length of the bars 0.1 to 0.15, breadth 0.004 to 0.005.

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

4. _Sagenoscena coronata_, n. sp.

Pyramids rather regular, usually four-sided (intermingled with single five-sided and six-sided forms); their axial rod and apical spines cylindrical, scarcely thicker than the smooth bars of the network. The distal end of the radial spines bears a corona of twenty to thirty curved terminal branches, which form a regular circle, and are armed with a spinulate terminal knob.

_Dimensions._--Diameter of the sphere 2 to 3, length of the bars 0.12 to 0.18, breadth 0.004 to 0.008.

_Habitat._--North Pacific, Station 256, surface.

5. _Sagenoscena spathillata_, n. sp.

Pyramids more or less irregular, of different sizes and various forms, each composed of four to eight convergent rods and a central axial rod. The latter is prolonged into a free apical spine, which bears at the distal end a spathilla of eight to twelve recurved teeth, and often beyond it a second similar verticil.

_Dimensions._--Diameter of the sphere 4.0, length of the bars 0.1 to 0.2, breadth 0.002.

_Habitat._--Arctic Ocean, Greenland (Olrik).

6. _Sagenoscena cruciata_, n. sp.

Pyramids very irregular, of different sizes and various forms, each composed of six to nine convergent rods and a central axial rod. The latter is prolonged into a free apical spine, which bears three to five cruciate verticils, each composed of four perpendicularly crossed lateral branches which bear at the distal end a spinulate knob (similar to _Sagmidium crucicorne_, Pl. 108, fig. 9).

_Dimensions._--Diameter of the sphere 1.0 to 1.2, length of the bars 0.06 to 0.09, breadth 0.001.

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

{1612}Subfamily 2. SAGMARIDA, Haeckel.

_Definition._--#Sagosphærida# with a spongy spherical shell, the thickened wall of which is composed of a loose spongy framework.

Genus 679. _Sagmarium_,[298] n. gen.

_Definition._--#Sagosphærida# with a spongy spherical shell, the thickened wall of which is composed of a loose spongy framework, and exhibits a smooth surface, without radial spines and pyramidal elevations.

The genus _Sagmarium_, and the following two genera of Sagosphærida, represent together the subfamily Sagmarida, differing from the preceding Sagenida in the spongy structure of the shell-wall. Whilst in the latter the thin wall of the delicate spherical shell is composed of a simple lattice-plate with triangular meshes, in the former numerous branches diverge from the nodal points of these meshes, and produce by union an irregular and loose spongy framework. The surface of this spongy hollow sphere (similar to _Plegmosphæra_) is in _Sagmarium_ smooth.

1. _Sagmarium spongodictyum_, n. sp. (Pl. 108, fig. 2).

Spongy wall of the hollow sphere about half as thick as the radius of its cavity. Bars of the spongy framework very thin and fragile, smooth, without thorns.

_Dimensions._--Diameter of the sphere 2.0 to 2.4; length of the bars 0.1 to 0.2, breadth 0.001.

_Habitat._--South Atlantic, Station 333, surface.

2. _Sagmarium plegmosphærium_, n. sp. (Pl. 108, fig. 14).

Spongy wall of the hollow sphere about one-fourth as thick as the radius of its cavity. Bars of the spongy framework rather stout, studded with numerous small spines, which arise perpendicularly from their surface.

_Dimensions._--Diameter of the sphere 1.2 to 1.5, length of the bars 0.1 to 0.16, breadth 0.004.

_Habitat._--Tropical Atlantic, Station 347, surface.

3. _Sagmarium trigonizon_, Haeckel.

_Dictyosoma trigonizon_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 841.

_Spongodictyon trigonizon_, Haeckel, 1863, Monogr. d. Radiol., p. 459,
Taf. xxvi. figs. 4, 5.

Bars of the spongy framework thin, irregularly curved, bearing scattered small crosses, which are composed of four small rods arising perpendicularly from the bars. Nodal points of the {1613}framework partly pierced by a hole. The peculiar network of a complete specimen, observed by me at Portofino in 1880, was so similar to that of _Spongodictyon trigonizon_, described above (p. 91), and figured in 1862 in my Monograph, that I am doubtful if the two forms are not identical, the two medullary shells of the latter being accidentally entangled in the framework. (Compare p. 1602.)

_Dimensions._--Diameter of the sphere 1.1 to 1.5, length of the bars 0.1 to 0.2, breadth 0.002.

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

Genus 680. _Sagmidium_,[299] n. gen.

_Definition._--Sagosphærida with a spongy spherical shell, the thickened wall of which is composed of a loose spongy framework, and bears on the nodal points of its surface radial spines.

The genus _Sagmidium_ differs from the preceding _Sagmarium_ in the development of radial spines on the surface of the spongy hollow sphere. It bears therefore the same relation to the latter as _Sagosphæra_ does to _Sagena_, and may be derived either from _Sagmarium_ by the formation of radial spines, or from _Sagosphæra_ by development of the spongy envelope.

1. _Sagmidium unicorne_, n. sp.