Legion I. SPUMELLARIA, (continued 2)

Dimensions.—Diameter of the central capsules 0.08 to 0.2, length of the simple spicula 0.1 to 0.15, of the geminate 0.08 to 0.16.

Habitat.—South Pacific, west coast of Patagonia, Station 302, surface.

8. Rhaphidozoum ascensionis, n. sp.

Spicula mixed, of two different kinds, simple needles and geminate-triradiate; both kinds thin, smooth, without spinules. Simple needles somewhat curved, C- or S-shaped. Geminate spicula double-triradiate, composed of a simple, short, straight axial rod and three slender curved shanks on each end of it. Shanks two to four times longer than the middle rod. (Sometimes few simple hexaradiate and geminate tetraradiate spicula are mingled.)

Dimensions.—Diameter of the central capsules 0.12 to 0.15, length of the simple spicula 0.1, of the double-triradiate 0.05 to 0.2.

Habitat.—South Atlantic, off Ascension Island, Station 342, surface.

9. Rhaphidozoum capense, n. sp.

Spicula of two different kinds; one kind simple, needle-shaped, straight, pointed at both ends, the other kind geminate-quadriradiate, with a stout short middle rod and four longer bent shanks on each end of it. Both kinds smooth.

Dimensions.—Diameter of the capsules 0.2 to 0.25, length of the simple needles 0.01 to 0.3, of the geminate spicula 0.05 to 0.15.

Habitat.—Cape of Good Hope (Agulhas), Station 142, surface.

10. Rhaphidozoum australe, n. sp.

Spicula of two different kinds; one kind simple, needle-shaped, curved, thin; the other kind geminate, with a variable number of shanks on both ends of the shorter middle rod, often different on the two poles of it. The prevalent number of rays on each end is three or four, often also two or five, rarely six. All spicula smooth, more or less bent.

Dimensions.—Diameter of the capsules 0.1 to 0.2, length of the spicula 0.05 to 0.15.

Habitat.—South West Pacific, Station 165, surface.

Subgenus 3. Rhaphidonura, Haeckel.

Definition.—Spicula of three different kinds: one kind simple, needle-shaped; the second kind radiate, with three to six shanks radiating from a common central point; the third kind geminate-radiate, with rays on both poles of a middle rod.

11. Rhaphidozoum polymorphum, n. sp.

Spicula of three different kinds; simple needles, radiate, and geminate mixed. The simple needles straight and stout. The radiate spicula commonly with three or six, rarely four or five, rays. The geminate-radiate spicula prevalent, with three or four, rarely two or five, shanks on each end of the middle rod. Number very variable. All shanks straight and smooth.

Dimensions.—Diameter of the capsule 0.1 to 0.2, length of the spicula 0.05 to 0.15.

Habitat.—South Pacific, Station 295, surface.

12. Rhaphidozoum pandora, n. sp. (Pl. 4, fig. 6).

Spicula of three different kinds; simple needles, radiate and geminate mixed. The simple needles thin spindle-shaped, often curved. The radiate spicula commonly with three or four, rarely five or six, curved rays. The geminate-radiate spicula commonly with three or four, rarely two or five, shanks on each end, often different on the two ends of the middle rod. Number and form very variable. All or most of the shanks more or less bent and thorny.

Dimensions.—Diameter of the capsule 0.1 to 0.3, length of the spicula 0.05 to 0.2.

Habitat.—South Atlantic (near Ascension Island), Station 343, surface.

Order II. SPHÆRELLARIA, Haeckel, 1881.

Definition.—Spumellaria with latticed or spongy shell.

The order Sphærellaria, the second order of Radiolaria, comprises all those Spumellaria in which the skeleton is a latticed or fenestrated, often more or less spongy, siliceous shell. Originally this shell is a simple extracapsular lattice-sphere, in which the central capsule is included; from this simple ancestral form an enormous mass of different and often very complicated forms is derived; this order is by far the largest, and in morphological respects the most important and most interesting, of all Radiolaria. It contains not less than twenty-eight different families, three hundred and five genera, and more than sixteen hundred species.

In my Monograph (1862) seven families appertaining to this group are described—the Ethmosphærida, Cladococcida, Ommatida, Spongurida, Discida, Lithelida, and Collosphærida. The astonishing increase of this group by the detection of a large series of new and interesting forms, and particularly of important connecting forms between very different branches of it, now enables me to give a much better arrangement. I discern now four suborders or sections of Sphærellaria, according to the different geometrical form of the central capsule and of the latticed shell enveloping it. The first of these, and the common ancestral group of the whole order, is the Sphæroidea, with spherical capsule; in the Prunoidea it becomes ellipsoidal or cylindrical by prolongation of one axis; in the Discoidea lenticular or discoidal by shortening of one axis; in the Larcoidea lentelliptical, or triaxon-ellipsoid, by different growth of the capsule in three different "dimensive axes."

Synopsis of the Four Suborders of Sphærellaria.

Central capsule spherical. Shell a simple sphere or a system of concentric spheres, 1. Sphæroidea.

Central capsule ellipsoidal or cylindrical. Shell a simple ellipsoid or a cylinder with annular transverse constrictions, 2. Prunoidea.

Central capsule lenticular or discoidal. Shell a biconvex lens or a flat disk, 3. Discoidea.

Central capsule lentelliptical or triaxon. Shell a triaxon-ellipsoid, with three different axes, 4. Larcoidea.

Central capsule spherical.

Shell a simple sphere or a system of concentric spheres,

1. Sphæroidea.

Central capsule ellipsoidal or cylindrical.

Shell a simple ellipsoid or a cylinder with annular transverse constrictions,

2. Prunoidea.

Central capsule lenticular or discoidal.

Shell a biconvex lens or a flat disk,

3. Discoidea.

Central capsule lentelliptical or triaxon.

Shell a triaxon-ellipsoid, with three different axes,

4. Larcoidea.

Suborder I. SPHÆROIDEA, Haeckel.

Definition.—Spumellaria with spherical central capsule (very rarely somewhat modified, or allomorphous); with spherical fenestrated siliceous shell (often an endospherical polyhedron, very rarely of more modified, subspherical form or allomorphous). Growth of the shell in the three dimensive axes equal.

The suborder Sphæroidea, the first and most important of the four of the Sphærellaria, comprises those Spumellaria in which the original geometrical spherical form is quite constantly preserved in the central capsule, and commonly also in the fenestrated shell enveloping the latter, although in many forms the sphere is more or less modified; very frequently it is an "endospherical polyhedron," i.e., a polyhedron all the angles (or the nodes of the network) of which lie upon the surface of a geometrical sphere; more rarely the spherical form is more or less modified and irregular. In the great majority of Sphæroidea there is no external indication of the three dimensive axes; but in many forms they are indicated by the regular position of certain external radial spines or internal radial beams. However, in no case are those three axes expressed in the form of the shell itself and of the enclosed spherical central capsule; this is the main character by which the Sphæroidea differ from the following sections:—Prunoidea, Discoidea, Larcoidea, all three of which arise from them.

The section Sphæroidea, in the sense here restricted, was founded by me in my Protistenreich (1878, p. 103) and adopted by Hertwig (1879) in his Organismus der Radiolarien (p. 39). The different groups appertaining to this large section were characterised more accurately in my Prodromus (1881, pp. 448-456); there I gave the characters of six subfamilies with thirty tribes, containing ninety-three genera. Formerly, in my Monograph (1862), the Sphæroidea were disposed in five different families:—Ethmosphærida, Cladococcida, Ommatida, Spongosphærida, Collosphærida. At that time I could not separate them sufficiently from some Acantharia and Phæodaria, which have a similar spherical lattice-shell.

As the number of different genera and species in the Sphæroidea is much greater than in all other sections of Spumellaria, many forms were already described by former authors. In the oldest system of Ehrenberg (1847, loc. cit., p. 53) they represent one part of his Haliommatina (with four genera, Haliomma, Chilomma, Stylosphæra, Spongosphæra). Most species, however, of these genera are Discoidea. Also in the latest system of Ehrenberg (1875, loc. cit., p. 157) his Haliommatina are a confused conglomeration of different Spumellaria (Sphæroidea, Discoidea, and Prunoidea).

The section Sphæroidea is the largest division of Sphærellaria, comprising not less than one hundred and seven genera and six hundred and fifty species. This enormous number (easily to be augmented by further investigations) requires a careful disposition in different families and subfamilies. For this disposition two different principles only can be employed: firstly, the number and disposition of the radial spines; secondly, the number of the concentric latticed spheres, which are connected by radial beams. I give here the preference to the first principle, whilst in my Prodromus (1881) I had preferred the second. The question, which of the two principles is more important for the classification of Sphæroidea, is very difficult to answer; probably in many cases the former, in many the latter is more important for their phylogeny.

Regarding the number of the concentric shells which compose the latticed carapace of the Sphæroidea, we can distinguish six families, viz.:—

On the other hand, regarding the number of the radial spines and their regular disposition on the shell-surface, we can distinguish five families, viz.:—

All five latter groups contain representatives of all six former groups; therefore we get together not less than thirty different subfamilies of Sphæroidea, already enumerated in my Prodromus, 1881, p. 449. I repeat them here to give a better survey of the system there employed.

Families and Subfamilies of SPHÆROIDEA. Liosphærida (anacantha). Stylosphærida (diacantha). Staurosphærida (tetracantha). Cubosphærida (hexacantha). Astrosphærida (polyacantha).

Monosphærida. (One single shell.) Ethmosphærida. Xiphostylida. Staurostylida. Hexastylida. Coscinommida.

Dyosphærida. (Two concentric shells.) Carposphærida. Sphærostylida. Staurolonchida. Hexalonchida. Haliommida.

Triosphærida. (Three concentric shells.) Thecosphærida. Amphistylida. Stauracontida. Hexacontida. Actinommida.

Tetrasphærida. (Four concentric shells.) Cromyosphærida. Cromyostylida. Staurocromyida. Hexacromyida. Cromyommida.

Polysphærida. (Five or more concentric shells.) Caryosphærida. Caryostylida. Staurocaryida. Hexacaryida. Arachnommida.

Spongosphærida. (Spongy shells.) Plegmosphærida. Spongostylida. Staurodorida. Hexadorida. Spongiommida.

Families and Subfamilies of SPHÆROIDEA. Liosphærida (anacantha). Stylosphærida (diacantha). Staurosphærida (tetracantha).

Monosphærida. (One single shell.) Ethmosphærida. Xiphostylida. Staurostylida.

Dyosphærida. (Two concentric shells.) Carposphærida. Sphærostylida. Staurolonchida.

Triosphærida. (Three concentric shells.) Thecosphærida. Amphistylida. Stauracontida.

Tetrasphærida. (Four concentric shells.) Cromyosphærida. Cromyostylida. Staurocromyida.

Polysphærida. (Five or more concentric shells.) Caryosphærida. Caryostylida. Staurocaryida.

Spongosphærida. (Spongy shells.) Plegmosphærida. Spongostylida. Staurodorida.

Families and Subfamilies of SPHÆROIDEA. Cubosphærida (hexacantha). Astrosphærida (polyacantha).

Monosphærida. (One single shell.) Hexastylida. Coscinommida.

Dyosphærida. (Two concentric shells.) Hexalonchida. Haliommida.

Triosphærida. (Three concentric shells.) Hexacontida. Actinommida.

Tetrasphærida. (Four concentric shells.) Hexacromyida. Cromyommida.

Polysphærida. (Five or more concentric shells.) Hexacaryida. Arachnommida.

Spongosphærida. (Spongy shells.) Hexadorida. Spongiommida.

The Monosphærida comprise all those Sphæroidea in which the carapace is represented only by one single lattice-shell. Originally this shell is probably everywhere an extracapsular or "cortical shell," which is developed on the outside of the jelly-veil enveloping the central capsule, and serves as a protective carapace for these soft enclosed parts. But with the progress of growth the central capsule becomes larger than the including shell, and sends out through its pores club-shaped prolongations or cæcal-sacs (Pl. 11, figs. 1, 5; Pl. 19, figs. 2, 3, 5; Pl. 20, fig. 1a; Pl. 27, fig. 3). These protruded sacs may fuse together again outside the shell and form a spherical bladder, now enveloping the smaller shell; the latter now becomes an intracapsular or "medullary shell."

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 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 (cœnobia). 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 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.

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 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 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.

Synopsis of the Families of Sphæroidea.

Surface of the spherical shell smooth, rough, or thorny, but not armed with radial spines. A. Liosphærida monozoa. Single cells (each with shell) living solitary. Spherical shell commonly quite regular, simple, or composed of two or more concentric spheres, 05. Liosphærida.

B. Liosphærida polyzoa. Aggregated cells (each with shell) living in colonies. Spherical shell commonly more or less irregular, simple (rarely composed of two concentric spheres), 06. Collosphærida.

Surface of the spherical shell armed with two, four, or six radial main spines, opposite in pairs in one, two, or three dimensive axes (always solitary). Two radial main-spines, opposite in one axis of the shell 07. Stylosphærida.

Four radial main-spines, opposite in pairs in two dimensive axes, perpendicular one to another, 08. Staurosphærida.

Six radial main-spines, opposite in pairs in three dimensive axes (perpendicular one to another), 09. Cubosphærida.

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.

Surface of the spherical shell smooth, rough, or thorny, but not armed with radial spines.

A. Liosphærida monozoa. Single cells (each with shell) living solitary.

Spherical shell commonly quite regular, simple, or composed of two or more concentric spheres,

5. Liosphærida.

B. Liosphærida polyzoa. Aggregated cells (each with shell) living in colonies.

Spherical shell commonly more or less irregular, simple (rarely composed of two concentric spheres),

6. Collosphærida.

Surface of the spherical shell armed with two, four, or six radial main spines, opposite in pairs in one, two, or three dimensive axes (always solitary).

Two radial main-spines, opposite in one axis of the shell

7. Stylosphærida.

Four radial main-spines, opposite in pairs in two dimensive axes, perpendicular one to another,

8. Staurosphærida.

Six radial main-spines, opposite in pairs in three dimensive axes (perpendicular one to another),

9. Cubosphærida.

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 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.) Pores of the shell simple, not prolonged into free tubuli. Shell cavity simple, 15. Cenosphæra.

Shell cavity with radial beams united in the centre, 16. Stigmosphæra.

Pores prolonged into free conical or cylindrical tubuli. Tubuli external, centrifugal, 17. Ethmosphæra.

Tubuli internal, 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 without latticed medullary shell in the centre. Sphere solid, 25. Styptosphæra.

Sphere with a central cavity, 26. Plegmosphæra.

Spongy sphere with one or two latticed medullary shells in the centre. One single medullary shell, 27. Spongoplegma.

Two concentric medullary shells, 28. Spongodictyon.

I. Subfamily Ethmosphærida. (Shell one single latticed sphere.)

Pores of the shell simple, not prolonged into free tubuli.

Shell cavity simple,

15. Cenosphæra.

Shell cavity with radial beams united in the centre,

16. Stigmosphæra.

Pores prolonged into free conical or cylindrical tubuli.

Tubuli external, centrifugal,

17. Ethmosphæra.

Tubuli internal, 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 without latticed medullary shell in the centre.

Sphere solid,

25. Styptosphæra.

Sphere with a central cavity,

26. Plegmosphæra.

Spongy sphere with one or two latticed medullary shells in the centre.

One single medullary shell,

27. Spongoplegma.

Two concentric medullary shells,

28. Spongodictyon.

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 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.

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. 1b). 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).

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.

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.

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 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.

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 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, 5a).

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.

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.)

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.

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, 3a, 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).

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.

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.

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. Phœnicosphæra, 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.

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, 2a).

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).

Both shells with the same number of pores, exactly corresponding, about ten on the quadrant. All pores regular, or subregular, hexagonal; the outer twice as broad as the inner. Outer bars very thin, thread-like; inner bars thick, one-third as broad as the pores. Surface smooth. Both shells connected by numerous radial beams, their distance one-third as large as the radius of the inner shell.

Dimensions.—Diameter of the outer shell 0.16, inner 0.12, distance of both 0.02; outer pores 0.014, inner pores 0.007.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

2. Liosphæra rhodococcus, n. sp.

Both shells with the same number of pores, exactly corresponding, about twelve on the quadrant. All pores regular or subregular; the inner circular, with elegant six-lobed frames, twice as broad as the bars; the outer hexagonal, with very thin thread-like bars. All corners of the outer and inner hexagons connected by thin, bristle-shaped radial beams. (Similar to Haliomma rhodococcus, Pl. 19, fig. 6; but with smooth surface and regular hexagonal pores of the outer shell.)

Dimensions.—Diameter of the outer shell 0.2, inner 0.16, distance of both 0.02; outer pores 0.03, inner 0.01.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

3. Liosphæra porulosa, n. sp.

Both shells with regular hexagonal pores; their number in the outer shell seven times as great as in the inner. Pores of the stout inner shell large, three times as broad as the bars, about eight on the quadrant. From each hexagon-corner arises one bristle-shaped radial beam; their distal ends are united by threads (three from each), forming the large meshes of the delicate outer shell. Each of these is divided by very thin threads into seven small circular porules, one central and six around it.

Dimensions.—Diameter of the outer shell 0.25, inner 0.2, distance of both 0.025; outer pores 0.04, their porules 0.012, inner pores 0.15.

Habitat.—Indian Ocean, Sunda Strait, Rabbe; surface.

Subgenus 2. Craspedomma, Haeckel.

Definition.—Pores of both shells irregular, in each shell differing either in form or size.

4. Liosphæra peridromium, n. sp.

Both shells with the same number of large, polygonal, very irregular pores, exactly corresponding (about eight to ten on the quadrant); both with a very delicate thin framework. From the thread-like bars of the inner, very large and thin-walled, sphere arise perpendicularly innumerable short bristles of equal length, which are united at equal distances by tangential thread-like bars, parallel to the former, composing the outer shell. Each mesh is, therefore, surrounded by a delicate ballister or rail.

Dimensions.—Diameter of the outer shell 0.42, inner 0.4, distance of both 0.01; diameter of the meshes 0.02 to 0.06.

Habitat.—North Pacific, Station 250, surface.

5. Liosphæra polypora, n. sp. (Pl. 20, fig. 2).

Both shells with small irregular roundish pores, of about the same size as the bars between them; twenty to thirty on the quadrant. The pores of the outer shell somewhat smaller, therefore much more numerous than the pores of the inner shell. Distance between the two shells about one-third as great as the radius of the inner. Both shells connected by numerous thin radial beams. Surface smooth or a little rough.

Dimensions.—Diameter of the outer shell 0.18, inner 0.14, distance of both 0.02; pores and bars 0.003 to 0.005.

Habitat.—West Tropical Pacific, Station 225, depth 4475.

Subfamily Thecosphærida,^[33] Haeckel, 1881, Prodromus, pp. 449, 452.

Definition.—Liosphærida with three concentric spherical lattice-shells, which are united by radial beams.

Genus 21. Thecosphæra,^[34] Haeckel, 1881, Prodromus, p. 452.

Definition.—Liosphærida with two medullary (intracapsular) shells and one cortical (extracapsular) shell.

The genus Thecosphæra comprises a large number of triple-shelled Sphæroidea, formerly united with Actinomma, but different from this genus in the absence of radial spines. The latticed shell is composed of three concentric spheres, two of which lie within the central capsule (medullary shells), and one outside (cortical shell). This latter is connected with the former by radial beams piercing the wall of the central capsule. From the following Rhodosphæra (with one medullary and two cortical shells) Carposphæra differs also by the distance of the three shells. In the former the distance between the two outer shells is much smaller, in the latter much larger, than the distance between the inner shells.

Subgenus 1. Thecosphærantha, Haeckel.

Definition.—Pores of the cortical shell regular, hexagonal, or circular, with hexagonal frames or lobes, all of nearly equal size and form.

1. Thecosphæra triplodictyon, n. sp.

Cortical shell thin walled, smooth, with regular, hexagonal pores, four times as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 8. Both medullary shells with regular circular pores, twice as broad as the bars, the inner half as broad as the outer. All three shells connected by six thin radial beams, opposite in pairs in the three dimensive axes.

Dimensions.—Diameter of the outer shell 0.2, middle 0.05, inner 0.025; cortical pores 0.012, bars 0.003.

Habitat.—Central Pacific, Station 271, surface.

2. Thecosphæra phænaxonia, n. sp.

Cortical shell thick walled, rough, with regular, circular, hexagonally framed pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 6. Both medullary shells with regular hexagonal pores and thin bars. All three shells connected by six prismatic radial beams, opposite in pairs in the three dimensive axes. (Shell similar to Hexacontium sceptrum, Pl. 24, fig. 1, 1a, but without external spines.)

Dimensions.—Diameter of the outer shell 0.12, middle 0.04, inner 0.02; cortical pores 0.01, bars 0.005.

Habitat.—North Pacific, Station 253, surface.

3. Thecosphæra favosa, n. sp.

Cortical shell thick walled, thorny, with regular, circular, hexagonally framed pores, of the same breadth as the bars. Radial proportion of the three spheres = 1 : 3 : 10. Both medullary shells with regular circular pores, connected with the former by twelve short prismatic, regularly disposed radial beams.

Dimensions.—Diameter of the outer shell 0.2, middle 0.06, inner 0.02; cortical pores and bars 0.008.

Habitat.—Central Pacific, Station 268, surface; also fossil in Barbados.

4. Thecosphæra floribunda, n. sp.

Cortical shell thick walled, smooth, with regular, elegantly six-lobed pores, three times as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 4. Both medullary shells with simple regular circular pores, connected with the former by six dimensive radial beams. (Similar to Hexacontium floridum, Pl. 24, fig. 4, but without external spines.)

Dimensions.—Diameter of the outer shell 0.12, middle 0.06, inner 0.03; cortical pores 0.01, bars 0.0033.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

Subgenus 2. Thecosphærella, Haeckel.

Definition.—Pores of the cortical shell regular, circular, without hexagonal frames or lobes, all of nearly equal size and form.

5. Thecosphæra inermis, Haeckel.

Actinomma inerme, Haeckel, 1862, Monogr. d. Radiol., p. 440, Taf. xxiv. fig. 5.

Haliomma inerme, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 815.

Cortical shell thin walled, rough, with regular circular pores, twice as broad as the bars. Radial proportion of the three spheres and of their circular regular pores = 1 : 2 : 4. All three spheres connected by twelve regularly disposed radial beams.

Dimensions.—Diameter of the outer shell 0.1, middle 0.05, inner 0.025; cortical pores 0.006, bars 0.003.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, at many Stations and at various depths.

6. Thecosphæra æquorea, Haeckel.

Haliomma æquorea, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 83; Mikrogeol., 1854, Taf. xxii. fig. 35.

Actinomma æquorea, Haeckel, 1862, Monogr. d. Radiol., p. 443.

Cortical shell thick walled, smooth, with regular circular pores of the same breadth as the bars. Radial proportion of the three spheres and of their regular pores = 1 : 2 : 6 or = 1 : 3 : 9; they are connected by six radial beams, opposite by pairs in the three dimensive axes.

Dimensions.—Diameter of the outer shell 0.08 to 0.12, middle 0.03 to 0.04, inner 0.09 to 0.12; cortical pores and bars about 0.006.

Habitat.—Mediterranean, Corfu, surface; fossil in Greece and Sicily.

7. Thecosphæra medusa, Haeckel.

Haliomma medusa, Ehrenberg, 1838, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 130; Mikrogeol., 1854, Taf. xxii. figs. 33, 34.

Actinomma medusa, Haeckel, 1862, Monogr. d. Radiol., p. 444.

Actinomma medusa, Stöhr, 1880, Palæontogr., Bd. xxvi. p. 90, Taf. ii. fig. 3.

Cortical shell thick walled, rough or thorny, with regular circular pores of the same breadth as the bars. Radial proportion of the three spheres = 1 : 2 : 4 (or 1 : 2.5 : 6); they are connected by four radial beams, crossed by pairs in two diameters, perpendicular one to another.

Dimensions.—Diameter of the outer shell 0.08 to 0.12, middle 0.04 to 0.06, inner 0.02 to 0.025; cortical pores and bars in average 0.005.

Habitat.—Fossil in Tertiary rocks of Barbados and the Mediterranean.

8. Thecosphæra entactinia, n. sp.

Cortical shell thick walled, smooth, with regular circular pores of the same breadth as the bars. Radial proportion of the three spheres = 1 : 3 : 12; they are connected by very numerous (forty to fifty, or more) thin radial beams.

Dimensions.—Diameter of the outer shell 0.24, middle 0.06, inner 0.02; cortical pores and bars 0.008.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

9. Thecosphæra micropora, n. sp.

Cortical shell thin walled, smooth, with very small and numerous, regular, circular pores, half as broad as the bars. Radial proportion of the three shells = 1 : 2 : 5; they are connected by twenty regularly disposed radial beams.

Dimensions.—Diameter of the outer shell 0.2, middle 0.08, inner 0.04; cortical pores 0.002, bars 0.004.

Habitat.—South Pacific, Station 288, surface.

Subgenus 3. Thecosphærina, Haeckel.

Definition.—Pores of the cortical shell irregular polygonal, of unequal size or dissimilar form.

10. Thecosphæra capillacea, n. sp.

Cortical shell thin walled, smooth, with irregular polygonal pores, three to six times as broad as the bars. Both medullary shells with similar, but smaller, pores. Radial proportion of the three spheres = 1 : 3 : 8; they are connected by very numerous (sixty to eighty or more) thin radial beams. (Similar to Actinomma capillaceum, Pl. 29, fig. 6, but without external spines.)

Dimensions.—Diameter of the outer shell 0.2, middle 0.075, inner 0.025; cortical pores 0.006 to 0.012, bars 0.002.

Habitat.—North Pacific, Station 250, surface.

11. Thecosphæra diplococcus, n. sp.

Cortical shell thick walled, rough, with large irregular polygonal pores, two to three times as broad as the bars. Both medullary shells with small regular circular pores. Radial proportion of the three spheres = 1 : 2 : 6; they are connected by twenty (?) stout radial beams.

Dimensions.—Diameter of the outer shell 0.12, middle 0.04, inner 0.02; cortical pores 0.008 to 0.012, bars 0.004.

Habitat.—South Atlantic, Station 330, surface.

Subgenus 4. Thecosphæromma, Haeckel.

Definition.—Pores of the cortical shell irregular, roundish, of unequal size or dissimilar form.

12. Thecosphæra dodecactis, n. sp.

Cortical shell thin walled, smooth, with large irregular roundish pores, two to eight times as broad as the bars. Both medullary shells with regular circular pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 5; they are connected by twelve regularly disposed stout radial beams.

Dimensions.—Diameter of the outer shell 0.2, middle 0.08, inner 0.04; cortical pores 0.004 to 0.016, bars 0.002.

Habitat.—Central Pacific, Station 263, depth 2650 fathoms.

13. Thecosphæra icosactis, n. sp.

Cortical shell thin walled, with small irregular roundish pores, two to four times as broad as the bars. Both medullary shells with similar but smaller pores. Radial proportion of the three spheres = 1 : 3 : 8; they are connected by twenty thin radial beams.

Dimensions.—Diameter of the outer shell 0.32, middle 0.12, inner 0.04; cortical pores 0.005 to 0.012, bars 0.003.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

14. Thecosphæra maxima, n. sp.

Cortical shell thin walled, with small irregular roundish pores, two to six times as broad as the bars. Both medullary shells with similar, but smaller, pores. Radial proportion of the three spheres = 1 : 3 : 9; they are connected by numerous (forty to sixty or more) thin radial beams.

Dimensions.—Diameter of the outer shell 0.45, middle 0.15, inner 0.05; cortical pores 0.008 to 0.024, bars 0.004.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Genus 22. Rhodosphæra,^[35] Haeckel, 1881, Prodromus, p. 452.

Definition.—Liosphærida with one medullary (intracapsular) shell and two cortical (extracapsular) shells.

The genus Rhodosphæra differs from the preceding Thecosphæra in the same manner in which, among the Dyosphærida, Liosphæra differs from Carposphæra. The cortical shell is double, composed of two not far distant shells, lying outside the central capsule. The distance between the shells is much smaller than the radius of the inner shell. This is connected by radial beams (piercing the central capsule) with the small central medullary shell.

Subgenus 1. Rhodosphærella, Haeckel.

Definition.—Pores of both cortical shells regular, in each shell all of nearly equal size and form.

1. Rhodosphæra hexagonia, n. sp.

Both cortical shells with the same number of regular hexagonal pores; the inner four times as broad as the bars, and half as broad as the outer pores, which are separated by thread-like bars. Medullary shell only one-fourth as broad as the inner cortical shell, with regular hexagonal pores of half the size. (Differs from the similar Liosphæra hexagonia, Pl. 20, fig. 3, by the possession of a medullary shell.)

Dimensions.—Diameter of the outer shell 0.2, middle 0.16, inner 0.04; outer pores 0.013, middle 0.008, inner 0.004.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Rhodosphæra melitomma, n. sp.

Both cortical shells with the same number of regular pores; the inner regular, circular, twice as broad as the bars, with elegant hexagonal frames and six roundish lobes alternating with the six radial spines which arise from the hexagon-corners; these short conical spines are connected at the distal end (at equal distances from the centre) by delicate threads (three from each spine), which form the delicate external shell. Medullary shell one-third as broad as the inner cortical shell, with small, simple, regular circular pores. (If in Carposphæra melitomma, Pl. 20, fig. 4, the distal ends of the spines became united by a cobweb-like outer shell, this species would be formed.)

Dimensions.—Diameter of the outer shell 0.22, middle 0.18, inner 0.06; outer pores 0.025, middle 0.0125, inner 0.005.

Habitat.—Central Pacific, Station 270, depth 2925 fathoms.

Subgenus 2. Rhodosphæromma, Haeckel.

Definition.—Pores of both cortical shells irregular, in each shell of unequal size or dissimilar form.

3. Rhodosphæra palliata, n. sp.

Both cortical shells with an unequal number of irregular roundish pores; the outer pores somewhat smaller and much more numerous than the inner pores; the bars between the latter are thicker. Medullary shell about one quarter as broad as the inner cortical shell, with regular circular pores.

Dimensions.—Diameter of the outer shell 0.4, middle 0.36, inner 0.08; outer pores on an average 0.008, middle 0.012, inner 0.004.

Habitat.—Fossil in Barbados.

4. Rhodosphæra pentaphylla, n. sp.

Both cortical shells with unequal number of irregular roundish pores; the inner pores large, three to four times as broad as the bars; to each inner pore corresponds a group of five smaller outer pores, like the five petals of a flower. Medullary shell half as broad as the inner cortical shell, with regular circular pores.

Dimensions.—Diameter of the outer shell 0.25, middle 0.2, inner 0.1; outer pores on an average 0.006, middle 0.012, inner 0.004.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Subfamily Cromyosphærida,^[36] Haeckel, 1881, Prodromus, pp. 449, 453.

Definition.—Liosphærida with four concentric spherical latticed shells, united by radial beams.

Genus 23. Cromyosphæra,^[37] Haeckel, 1881, Prodromus, p. 453.

Definition.—Liosphærida with two intracapsular (medullary) shells and two extracapsular (cortical) shells; the former united with the latter by radial beams piercing the wall of the central capsule.

The genus Cromyosphæra is the only known genus of Cromyosphærida, or of such Sphæroidea, the smooth shell of which is composed of two medullary and two cortical shells. There may possibly be other Cromyosphærida, in which the shell is composed of one simple medullary and three cortical shells, or only of four extra-capsular cortical shells; but such have not as yet been observed. Caryosphæra polysphærica, Bütschli, 1882 (L. N. 41, Taf. xxiii. fig. 12) is probably a Cromyosphæra (fossil in Barbados).

1. Cromyosphæra quadruplex, n. sp. (Pl. 30, fig. 9).

Radial proportion of the four spheres = 1 : 2 : 4 : 5. Outer cortical shell smooth, with large regular hexagonal pores, ten times as broad as the bars; inner cortical shell with irregular polygonal pores, five times as broad as the bars. Both medullary shells with regular circular pores of the same breadth as the bars.

Dimensions.—Diameter of the four spheres—(A) 0.16, (B) 0.12, (C) 0.06, (D) 0.03.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Cromyosphæra rosetta, n. sp.

Radial proportion of the four spheres = 1 : 2 : 8 : 10. Outer cortical shell smooth, with regular hexagonal pores and very thin bars; inner cortical shell with the same number of exactly corresponding, regular circular, hexagonally framed pores, twice as broad as the bars; the corners of the outer and inner hexagons united by radial bristles. Both medullary shells with regular circular pores, twice as broad as the bars.

Dimensions.—Diameter of the four spheres—(A) 0.2, (B) 0.16, (C) 0.04, (D) 0.02.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

3. Cromyosphæra bigemina, n. sp.

Radial proportion of the four spheres = 1 : 2 : 7 : 8. Outer cortical shell smooth, with regular hexagonal pores and very thin bars; inner cortical shell with the same number of exactly corresponding, regular circular pores. Both medullary shells with regular circular pores of the same breadth as the bars. (Somewhat similar to Hexacromyon elegans, Pl. 24, fig. 9, also with six inner radial beams, but without external radial spines.)

Dimensions.—Diameter of the four spheres—(A) 0.2, (B) 0.17, (C) 0.05, (D) 0.025.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

4. Cromyosphæra cepa, n. sp.

Radial proportion of the four spheres = 1 : 2 : 4 : 5. All four shells of the same structure, thick-walled, with regular circular pores, two to four times as broad as the bars; the size of the pores increases gradually from the inner to the outer shell. Surface thorny. Distance between the second and third shells twice as great as that between the others.

Dimensions.—Diameter of the four spheres—(A) 0.125, (B) 0.1, (C) 0.05, (D) 0.025.

Habitat.—Fossil in Barbados.

5. Cromyosphæra scorodonium, n. sp.

Radial proportion of the four spheres = 1 : 2 : 3 : 4. All four shells of the same structure, thin-walled, with irregular roundish pores, two to four times as broad as the bars; the size of the pores increasing gradually from the inner to the outer shell. Surface smooth. Distance between each two shells equal to the diameter of the innermost.

Dimensions.—Diameter of the four spheres—(A) 0.12, (B) 0.09, (C) 0.06, (D) 0.03.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms; also fossil in Barbados.

6. Cromyosphæra antarctica, n. sp..

Radial proportion of the four spheres = 1 : 2 : 5 : 7. Both cortical shells with irregular polygonal roundish pores; the outermost with thinner bars and rough surface, the inner with thicker bars. Both medullary shells with irregular roundish pores.

Dimensions.—Diameter of the four spheres—(A) 0.18, (B) 0.12, (C) 0.05, (D) 0.025.

Habitat.—Antarctic Ocean; in very large number, together with Rhizosphæra antarctica, in the diatomaceous ooze of Station 157 (3rd March 1874); depth 1950 fathoms.

Subfamily Caryosphærida,^[38] Haeckel, 1881, Prodromus, pp. 449, 454.

Definition.—Liosphærida with numerous (five or more) concentric spherical latticed shells, united by radial beams.

Genus 24. Caryosphæra,^[39] Haeckel, 1881, Prodromus, p. 454.

Definition.—Liosphærida with two intracapsular (medullary) shells and three or more extracapsular (cortical) shells; the former united with the latter by radial beams piercing the wall of the central capsule.

The genus Caryosphæra, the only observed form of this subfamily, comprises those Liosphærida in which the shell is composed of two medullary and three or more cortical shells. Such forms (without radial spines) are very rare; I observed only two species, one with five, the other with six shells. They are derived from Cromyosphæra by further apposition of outer cortical shells.

1. Caryosphæra pentalepas, n. sp.

Shell composed of five concentric spheres, with radial proportion = 1 : 2 : 8 : 10 : 12. Both medullary shells with regular circular pores, twice as broad as the bars. First cortical shell with regular, circular, hexagonally framed pores, three times as broad as the bars; second cortical shell with regular hexagonal pores, four times as broad as the bars; third (outermost) cortical shell with regular hexagonal pores and very thin thread-like bars. Surface smooth.

Dimensions.—Diameter of the five shells—(A) 0.02, (B) 0.04, (C) 0.16, (D) 0.2, (E) 0.24.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

2. Caryosphæra hexalepas, n. sp.

Shell composed of six concentric spheres, with the radial proportion = 1 : 2 : 4 : 5 : 6 : 8. All six shells with regular circular pores, two to four times as broad as the bars, with increasing size from the centrum against the smooth surface.

Dimensions.—Diameter of the six shells—(A) 0.025, (B) 0.05, (C) 0.1, (D) 0.13, (E) 0.16, (F) 0.2.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms; also fossil in Barbados.

Subfamily Plegmosphærida,^[40] Haeckel, 1881, Prodromus, p. 455.

Definition.—Liosphærida with spongy spherical shell, with or without latticed medullary shell in the centre.

Genus 25. Styptosphæra,^[41] Haeckel, 1881, Prodromus, p. 455.

Definition.—Liosphærida forming a solid sphere of spongy framework, without enclosed medullary shell, and without central cavity.

The genus Styptosphæra presents a spherical shell with smooth or rough surface (without radial spines), the whole mass of which is composed of looser or denser spongy wicker-work.

1. Styptosphæra spumacea, n. sp.

Spongy framework of the solid sphere loose, with large polygonal meshes of slightly different size, ten to twenty times as broad as the bars. Structure of the whole spongy sphere the same. Central capsule filled with crystals. Surface smooth.

Dimensions.—Diameter of the sphere 0.32, of the central capsule 0.26, meshes 0.01 to 0.02, bars 0.001.

Habitat.—North Pacific, Station 236, surface.

2. Styptosphæra spongiacea, n. sp.

Spongy framework in the central part of the solid sphere much more compact than in the peripheral part, becoming gradually looser towards the rough surface. Meshes in the centre three to five times, in the periphery fifteen to twenty times as broad as the bent bars.

Dimensions.—Diameter of the sphere 0.45, inner meshes 0.006 to 0.01, outer meshes 0.03 to 0.04, bars 0.002.

Habitat.—Central Pacific, Station 271, surface.

3. Styptosphæra stupacea, n. sp.

Spongy framework of the solid sphere rather compact, everywhere of the same structure, with roundish, nearly equal meshes, six to eight times as broad as the bars. Surface rough with prominent thorns.

Dimensions.—Diameter of the sphere 0.22, meshes 0.01 to 0.012, bars 0.0015.

Habitat.—South Pacific, Station 291, surface.

Genus 26. Plegmosphæra, Haeckel,^[42] 1881, Prodromus, p. 455.

Definition.—Liosphærida forming a hollow sphere of spongy framework, without a medullary shell in the central cavity.

The genus Plegmosphæra develops a large hollow sphere, the wall of which is composed of looser or denser spongy wicker-work. On the inner as well as on the outer face of the spongy shell-wall may be present a simple lattice-sphere from which the threads of the framework arise; but in some species these lattice-plates are quite absent.

Subgenus 1. Plegmosphærantha, Haeckel.

Definition.—Inside and outside of the spongy shell-wall smooth, closed by a lattice-plate with polygonal meshes.

1. Plegmosphæra maxima, n. sp.

Radius of the spherical shell-cavity eight to ten times as great as the thickness of the thin spongy wall. Inside and outside of the wall smooth, closed by a lattice-plate with irregular polygonal meshes. Only three or four meshes in the thickness of the wall.

Dimensions.—Diameter of the spongy sphere 0.8 to 1.0 mm., of its inner cavity 0.7 to 0.8, meshes 0.01 to 0.02, bars 0.002 to 0.003, central capsule 0.5 to 0.6, nucleus 0.1 to 0.15.

Habitat.—Central Pacific, Station 271, surface.

2. Plegmosphæra coelopila, n. sp.

Radius of the spherical shell-cavity eight to ten times as great as the thickness of the spongy wall. Inside and outside of the wall closed by a smooth lattice-plate with irregular polygonal meshes, five to ten times as broad as the bars.

Dimensions.—Diameter of the shell 0.32, of its cavity 0.26, meshes 0.01 to 0.02, bars 0.002.

Habitat.—North Atlantic, Færöe Channel, Gulf Stream, John Murray.

3. Plegmosphæra pachypila, n. sp.

Radius of the spherical shell-cavity about equal to the thickness of the spongy wall. Inside and outside of the wall closed by a smooth lattice-plate with irregular polygonal meshes, three to six times as broad as the bars.

Dimensions.—Diameter of the shell 0.24, of its cavity 0.12.

Habitat.—North Pacific, Station 250, surface.

Subgenus 2. Plegmosphærella, Haeckel.

Definition.—Inside of the spongy shell-wall closed by a smooth lattice-plate, outside rough, spongy, with prominent thorns.

4. Plegmosphæra entodictyon, n. sp.

Radius of the spherical shell-cavity half as great as the thickness of the spongy wall. Inside of the wall closed by a smooth lattice-plate, outside rough, spongy.

Dimensions.—Diameter of the shell 0.24, of its cavity 0.08.

Habitat.—South Pacific, Station 300, surface.

5. Plegmosphæra leptodictyon, n. sp.

Radius of the spongy shell-cavity six times as great as the thickness of the spongy wall. Inside of the wall closed by a smooth lattice-plate, outside rough spongy.

Dimensions.—Diameter of the shell 0.44, of its cavity 0.36.

Habitat.—Central Pacific, Station 266, surface.

Subgenus 3. Plegmosphæromma, Haeckel.

Definition.—Inside of the spongy shell-wall rough spongy, without lattice-plate, outside closed by a smooth lattice-plate.

6. Plegmosphæra exodictyon, n. sp. (Pl. 18, fig. 8).

Radius of the spongy shell-cavity only one-fourth as great as the thickness of the spongy shell-wall. Outside of the wall closed by a smooth lattice-plate, inside rough, spongy.

Dimensions.—Diameter of the shell 0.4, of its cavity 0.08.

Habitat.—South Atlantic, Station 325, surface.

Subgenus 4. Plegmosphærusa, Haeckel.

Definition.—Inside and outside of the spongy shell-wall rough, with spongy or spiny surface, without lattice-plate.

7. Plegmosphæra leptoplegma, n. sp.

Radius of the spherical shell-cavity half as great as the thickness of the loose spongy shell-wall. Inside and outside of the wall rough spongy, not closed by a lattice-plate. Meshes ten to twenty times as broad as the bars.

Dimensions.—Diameter of the shell 0.3, of its cavity 0.088.

Habitat.—North Atlantic, Station 253, surface.

8. Plegmosphæra pachyplegma, n. sp.

Radius of the spherical shell-cavity about equal to the thickness of the dark and dense spongy shell-wall. Inside and outside of the wall rough spongy, not closed by a lattice-plate. Meshes three to five times as broad as the bars.

Dimensions.—Diameter of the shell 0.2, of its cavity 0.1.

Habitat.—Central Pacific, Station 270, surface.

Genus 27. Spongoplegma,^[43] Haeckel, 1881, Prodromus, p. 455.

Definition.—Liosphærida forming a sphere of spongy framework, which encloses in the centre one single latticed medullary shell.

The genus Spongoplegma may be regarded as a Carposphæra, in which the simple latticed cortical shell is represented by an irregular spongy framework, immediately enclosing the simple latticed medullary shell.

1. Spongoplegma antarcticum, n. sp.

Cortical shell with loose spongy framework and rough surface, four to six times as broad as the enclosed simple medullary shell. Pores of the latter regular circular, twice as broad as the bars. From its surface arise numerous (forty to fifty or more) short radial beams, which become forked and compose, by communication of lateral branches, the spongy cortical shell.

Dimensions.—Diameter of the spongy cortical shell 0.2 to 0.3 of the latticed medullary shell 0.05 to 0.06.

Habitat.—Antarctic Ocean, in large number, together with Cromyosphæra antarctica; in the Diatom ooze of Station 157 (depth 1950 fathoms).

Genus 28. Spongodictyon,^[44] Haeckel, 1862, Monogr. d. Radiol., p. 459.

Definition.—Liosphærida forming a sphere of spongy framework, which encloses in the centre a double latticed concentric medullary shell.

The genus Spongodictyon can be regarded as a Thecosphæra, in which the simple latticed cortical shell is represented by an irregular spongy framework, which immediately encloses the double latticed medullary shell. Sometimes this latter appears triple, the inner surface of the spongy cortical shell forming a smooth spherical lattice-plate, separated by an interval from the double medullary shell.

Subgenus 1. Dictyoplegma, Haeckel, 1862, Monogr. d. Radiol, p. 458.

Definition.—Spongy cortical shell enveloping immediately the double medullary shell.

1. Spongodictyon spongiosum, Haeckel.

Dictyosoma spongiosum, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 31, Taf. ii. figs. 9-11.

Dictyoplegma spongiosum, Haeckel, 1862, Monogr. d. Radiol., p. 458.

Spongy framework of the cortical shell loose, with large, polygonal roundish meshes, on an average as large as the double medullary shell, which is immediately enveloped by it. Both concentric medullary shells with subregular roundish pores, twice as broad as the bars.

Dimensions.—Diameter of the cortical shell 0.2 to 0.3 or more; of the outer medullary shell 0.03, inner 0.01.

Habitat.—Mediterranean (French south coast, surface), J. Müller.