Legion IV. PHÆODARIA, (continued 5)

Dimensions.—Length of the shell 0.2, breadth 0.7.

Habitat.—South Pacific, Station 318, depth 2040 fathoms.

4. Gorgonetta bisenaria, n. sp.

Shell campanulate, similar to that of Gazelletta melusina (Pl. 118, fig. 1), with smooth surface. Six ascending feet about as long as the shell, nearly straight, similar to those of Gorgonetta mirabilis (Pl. 119, fig. 1). Six descending feet also similar to those of the latter, but shorter, about twice as long as the shell, strongly curved, studded with numerous small pencils, each thread of which has a double spathilla with three teeth. The distal end of each foot bears a whorl of six to eight irregular forked branches.

Dimensions.—Length of the shell 0.5, breadth 0.4.

Habitat.—Central Pacific, Station 263, surface.

Genus 704. Polypetta,^[321] n. gen.

Definition.—Medusettida with numerous (ten to twenty or more) articulate feet.

The genus Polypetta comprises those Medusettida in which the number of feet is very large and not limited, usually twenty to thirty or more. The few specimens of this genus that have been observed are rather different; and it may be that only the two first species described in the following lines are true Medusettida; they possess the usual distinctly alveolate feet, and are derived from the similar Medusetta or Gazelletta simply by multiplication of the feet. The two other species, however (figured in Pl. 116, figs. 1, 2, as Porospathis), belong perhaps to another family of Phæodaria (Castanellida?); their shell-structure is peculiar and their feet not distinctly alveolate; they may therefore represent a peculiar genus Porospathis (Haeckel, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, 1879, p. 5).

1. Polypetta polynema, n. sp.

Shell campanulate, thorny, about as long as broad, with slightly constricted mouth, similar to that of Gazelletta orthonema (Pl. 120, fig. 10). Shell-wall hollow, with irregular polygonal alveoles. Peristome with a corona of eighteen divergent, curved, cylindrical feet of unequal size; six larger primary on the margin of the shell, the other twelve secondary, between the former, somewhat above the margins at different heights. The feet are two to three times as long as the shell, irregularly curved and distinctly alveolate, without appendages.

Dimensions.—Length of the shell 0.12, breadth 0.11.

Habitat.—Central Pacific, Station 266, surface.

2. Polypetta alveolata, n. sp.

Shell campanulate, thorny, about as long as broad, very similar to that of Medusetta craspedota (Pl. 120, fig. 4). Shell-wall hollow, with subregular hexagonal alveoles. Peristome prolonged into a short funnel-shaped proboscis, twice as long as the similar velum of the latter. The velum is surrounded by a corona of eight larger and eight to twelve smaller feet; the larger are about as long as the shell, divergent, irregularly curved, thorny, and distinctly alveolate; the smaller feet are scattered above the latter and form an immediate transition to the small spines of the shell-surface.

Dimensions.—Length of the shell 0.08, breadth 0.09.

Habitat.—South Pacific, Station 284, surface.

3. Polypetta tabulata, n. sp. (Pl. 116, figs. 2, 2a, 2b).

Porospathis tabulata, Hæckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12.

Shell subspherical, with elegantly panelled or tabulate surface, composed of small triangular plates, which are separated by a network of prominent crests; at each nodal point of the network a small conical thorn arises (figs. 2a, 2b). Each triangular plate seems to contain a hollow alveole, which opens into the shell-cavity (?). On the surface of the shell are scattered numerous (thirty to forty or more), cylindrical, hollow, radial spines, which are straight or slightly curved, not distinctly alveolate, and increase in size towards the mouth. The aboral spines are scarcely one-third as long as the radius of the shell, whilst the oral spines are three times as long as its diameter. The proboscis of the constricted mouth is a hollow cylinder, longer than the shell-radius, and armed with a corona of fifteen to twenty slender bristle-shaped teeth. The position of this singular species in this family is doubtful.

Dimensions.—Diameter of the shell 0.1 to 0.11, length of the peristome 0.07, breadth 0.02.

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

4. Polypetta mammillata, n. sp. (Pl. 116, figs. 1, 1a).

Porospathis mammillata, Hæckel, 1879, Sitzungsb. med.-nat., Gesellsch. Jena, Dec. 12.

Shell subspherical, densely covered with numerous mammiliform hollow papillæ, between which are scattered single longer, hollow, radial spines; these are irregularly curved, cylindrical, without distinct alveoles; the twelve longest are two to three times as long as the shell, divergent in the oral direction, and surround the base of the peristome in two irregular alternate circles, each with six spines. The hollow papillæ of the surface, between which are placed numerous circular pores (or dimples?), open into the shell-cavity by a small pore (fig. 1a); they are perhaps reduced radial spines. The constricted peristome is conical and prolonged into an inversely conical proboscis, which is about as long as the radius of the shell; its dilated mouth is surrounded by a corona of slender, divergent, bristle-shaped teeth. The position of this species in the family Medusettida is doubtful; perhaps it is more closely allied to the Castanellida.

Dimensions.—Diameter of the shell 0.12; length of the proboscis 0.08, breadth 0.03; length of the shorter spines 0.1, of the longest spines 0.3.

Habitat.—North Pacific, Station 252, surface.

Family LXXX. Castanellida, Haeckel, 1879 (Pl. 113).

Definition.—Phæodaria with a spherical or subspherical shell, exhibiting ordinary lattice-work, with circular or roundish pores. Radial spines without circles of basal pores. Mouth of the shell large, usually circular and armed with teeth. Central capsule excentric, placed in the aboral half of the shell-cavity.

The family Castanellida represents a common and widely distributed group of Phæodaria, which posses a very simple and uniform shell, viz., a simple lattice-sphere with radial spines and one simple mouth. It may therefore be easily confounded with the Coscinommida, or those Sphæroidea in which the shell is also a simple lattice-sphere armed with radial spines (Astrosphærida simplicia, p. 209). Indeed the shell of both groups is very similar, and differs in one important point only; the Castanellida constantly possess one larger opening in the shell-wall, the shell-mouth, which is either smooth or armed with a corona of teeth; in the Coscinommida, however, such a mouth is never present. The living specimens of both groups, and those shells in which the soft body is preserved, are very easily distinguished, since the shell encloses in the Coscinommida the central capsule and the transparent calymma only, whilst the latter, besides, in the Castanellida contains a voluminous dark brown or green mass of phæodella, the characteristic phæodium. A closer examination of the central capsule reveals in all Castanellida the typical operculum, the astropyle, with the proboscis of the Phæodaria, which is never present in any Sphæroidea.

The Castanellida are easily distinguished also from those similar Phæodaria in which the shell is also a lattice-sphere; the lattice-work is constantly quite simple, as in the similar Coscinommida, never composed of separated tangential pieces (as in the Aulosphærida), or of porcellanous structure, with basal circles of pores (as in the Circoporida), or of diatomaceous structure (as in the Challengerida). The gigantic Orosphærida, which also in part posses a simple lattice-sphere, differ from the Castanellida in the absence of the peculiar shell-mouth.

Though the Castanellida belong to the most common Phæodaria, and though the number of individuals, floating on the surface of the tropical seas, is extraordinarily great, their variety of forms is very small; the six genera distinguished in the following system differ only in very slight characters, and the majority of the species are very similar, and often hardly distinguishable. The seven species figured in Pl. 113 exhibit the most striking differences which I could distinguish among all the species observed. The shell usually has the characteristic appearance of a chestnut, a sphere covered with very numerous short radial spines or bristles. In the majority of species a certain number of longer thin radial spines is scattered over the surface; these are usually simple, rarely branched. The mouth of the shell, corresponding to the proboscis of the central capsule, and placed in the same radius, is either a quite simple larger opening with a smooth margin (figs. 3, 5, 7) or is armed with a corona of teeth (figs. 1, 6).

The size of the shell varies between 0.2 and 0.8 mm., and is usually between 0.3 and 0.5 mm. Its form is in the majority of species a geometrical sphere; rarely it is somewhat irregular, slightly ellipsoidal (prolonged in the axis of the mouth and proboscis), or polyhedral (by conical protuberances from the bases of the radial spines). The ideal fundamental form of the shell, however, is constantly monaxonian, since the place of the shell-mouth and of the proboscis of the capsule (both lying in one axis of the sphere), causes a principal axis to be different from all others. The longer radial spines, quite variable in number and disposition, are never arranged regularly or symmetrically, and therefore determine no constant axes.

The lattice-work of the spherical shell offers also but slight differences. It is usually more or less irregular, with circular or subcircular pores of unequal sizes. More rarely the network is perfectly regular, with equidistant circular pores of equal size, and sometimes these are surrounded by hexagonal frames (fig. 6), as in many Sphæroidea. More rarely the pores are perfectly irregular, roundish or sometimes polygonal, of unequal sizes and dissimilar forms (fig. 2). The size of the pores is very variable between 0.01 and 0.05, usually between 0.015 and 0.025. They are commonly somewhat broader than the bars between them, more rarely smaller. The substance of the shell-wall is in the the majority of Castanellida hyaline, transparent (as in the similar Sphæroidea); in some larger forms, however, a network of fine axial filaments is visible in the lattice (fig. 2), and sometimes this seems to be hollow, with an axial canal (as in the large Orosphærida). Such an axial filament or fine axial canal is usually visible in the larger radial spines. The shell-wall of the Castanellida, however, never exhibits that characteristic structure (with tangential needles in a cement-like fundamental substance), which we find in all Circoporida. The latter differ also in the constant presence of circles of large pores around the bases of the radial spines, which are never found in the Castanellida. The shell becomes usually stained more or less purple by carmine, and when burned by fire, becomes of a brown colour.

The inner surface of the shell is always quite smooth, the outer surface armed with numerous short and thin radial bristles. Sometimes these bristles or "by-spines" are very short, but never perfectly wanting. Usually their length is about one-third or one-fourth of the radius of the shell, often less, rarely more. They arise from the nodal points between every three or four neighbouring spines, and are commonly very thin and straight, pointed, with slightly thickened conical basis. Rarely they are directed not quite radially, but more or less obliquely.

The larger radial spines, which arise between the thin bristles or "by-spines" and may be opposed to the latter as "main-spines," are wanting in two genera only, in Castanarium and Castanella (Pl. 113, fig. 6). They are simple in Castanidium (figs. 2, 5, 7) and Castanissa (fig. 1), irregularly branched in Castanopsis and Castanura (figs. 3, 4). Their number and disposition is never regular nor symmetrical (as in the majority of Sphæroidea) and varies even in each single species. In general the number of main-spines varies between ten and forty (rarely less or more) usually between twenty and thirty. Their length is commonly about equal to the diameter of the shell, often somewhat shorter, rarely considerably longer. Their thickness is in the majority of species about equal to the diameter of one or two pores of the lattice. Sometimes they are much stronger, rarely thinner.

The form of the radial main-spines is not very variable, usually it is cylindrical or cylindro-conical, rarely angular, prismatic or pyramidal. Sometimes they are straight (perfectly radial), at other times more or less irregularly curved. Usually they are simple, rarely branched; the branches are always very irregular and exhibit a remarkable tendency to unite by concrescence (figs. 3, 4). Some thicker forms of spines exhibit a remarkable structure, the surface being covered with small dimples and spinules between them (fig. 1); sometimes the dimples are hexagonal (fig. 5a). In the axis of the thicker spines there is often visible the same axial filament or funicle which we find in many other Phæodaria, more rarely a hollow axial canal.

The mouth of the shell is usually circular, more rarely polygonal or irregularly roundish (fig. 2). It is either quite smooth (fig. 3, 5, 7) or armed with a corona of strong teeth (figs. 1, 4, 6). These teeth are different from the other spines of the shell; they are much thicker than the radial bristles, and shorter than the main-spines. Their number varies between three and twenty, usually between five and seven. They are usually parallel to the main axis, which is determined by the excentric position of the mouth and the centre of the sphere (figs. 1, 6). The teeth are usually conical, more or less irregular in size and form, more rarely of equal size. The corona of teeth is usually sharply separated from the surrounding lattice-work of the shell, but has no influence on its regular spherical form.

The central capsule of the Castanellida immediately determines beyond doubt their true Phæodarian nature; it lies excentrically in the cavity of the enclosing shell, and is surrounded at the oral pole by the large and dark phæodium. The latter covers the radiate operculum of the capsule membrane and the tubular proboscis, which arises from it and is directed towards the shell mouth. Usually the diameter of the spherical central capsule is about one-third of the shell diameter, rarely one-quarter only, and in a few cases it attains nearly its half. The calymma, therefore, is larger than the capsule, and fills up the whole cavity of the shell which is not occupied by the latter. The greater part of the calymma again is filled up by the dark green or brown, sometimes black phæodella, the roundish granules which compose the voluminous non-transparent phæodium. Sometimes the latter proceeds through the mouth and is partially placed outside the shell (fig. 5).

The astropyle, or the main-opening of the central capsule, is placed on the oral pole of its main axis, while its radiate operculum and the tubular proboscis arising from it possess the same structure as in the other Phæodaria. But the two lateral parapylæ or accessory openings which are present in the majority of the latter seem to be absent in the Castanellida as well as in the Medusettida and the Challengerida. I could never observe a trace of them. The proboscis is a small cylindrical tube and is directed towards the mouth of the shell, therefore placed in its main axis; it is usually quite hidden in the dark phæodium, which occupies the oral half of the shell-cavity, whilst the capsule lies in the aboral half. The large nucleus of the central capsule and its double membrane present the same characters as in the other Phæodaria.

Synopsis of the Genera of Castanellida.

No long radial main-spines (in addition to the constant short bristles of the shell-surface). Mouth smooth, 705. Castanarium.

Mouth dentate, 706. Castanella.

Long radial main-spines scattered between the short constant bristles of the shell-surface. Main spines simple. Mouth smooth, 707. Castanidium.

Mouth dentate, 708. Castanissa.

Main spines branched. Mouth smooth, 709. Castanopsis.

Mouth dentate, 710. Castanura.

No long radial main-spines (in addition to the constant short bristles of the shell-surface).

Mouth smooth,

705. Castanarium.

Mouth dentate,

706. Castanella.

Long radial main-spines scattered between the short constant bristles of the shell-surface.

Main spines simple.

Mouth smooth,

707. Castanidium.

Mouth dentate,

708. Castanissa.

Main spines branched.

Mouth smooth,

709. Castanopsis.

Mouth dentate,

710. Castanura.

Genus 705. Castanarium,^[322] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Castanellida without radial main-spines, with a smooth mouth.

The genus Castanarium is the simplest form of all the Castanellida, and may be regarded as the common ancestral form of this family. The simple spherical shell has a smooth, toothless mouth and no larger radial spines; it is densely studded with the simple, radial bristles, which are common to all Castanellida. The shell therefore is very similar to those species of the Astrosphæride Acanthosphæra, which represent the subgenus Rhapidococcus (compare above, p. 210, Pl. 26, fig. 3); it differs from the latter in the possession of the shell-mouth, which is absent in all Sphæroidea.

1. Castanarium darwini, n. sp.

Pores regular, circular, hexagonally framed, three times as broad as the bars. Radial bristles half as long as the radius.

Dimensions.—Diameter of the shell 0.3 to 0.4, of the pores 0.03.

Habitat.—South Atlantic (east of Patagonia), Station 318, depth 2040 fathoms.

2. Castanarium hookeri, n. sp.

Pores regular, circular, hexagonally framed, twice as broad as the bars. Radial bristles one-third as long as the radius.

Dimensions.—Diameter of the shell 0.55, of the pores 0.025.

Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.

3. Castanarium lyelli, n. sp.

Pores regular, circular, without hexagonal frames, of the same breadth as the bars. Radial bristles twice as long as the diameter of one pore.

Dimensions.—Diameter of the shell 0.24, of the pores 0.015.

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

4. Castanarium lubbocki, n. sp.

Pores irregularly roundish, about of the same breadth as the roundish, non-crested bars. Radial bristles one-third as long as the radius.

Dimensions.—Diameter of the shell 0.36, of the pores 0.01 to 0.02.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

5. Castanarium huxleyi, n. sp.

Pores irregularly polygonal, two to three times as broad as the bars, separated by prominent polygonal crests. Radial bristles half as long as the radius.

Dimensions.—Diameter of the shell 0.45, of the pores 0.02 to 0.05.

Habitat.—South Pacific (off Australia), Station 165, surface.

Genus 706. Castanella,^[323] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Castanellida without radial main-spines, with a dentate mouth.

The genus Castanella comprises the most common and most widely distributed species of Castanellida. It agrees in general shape with its ancestral form, the preceding Castanarium, differing from it only in the possession of strong teeth, which form a corona around the mouth.

1. Castanella wyvillei, n. sp. (Pl. 113, fig. 6).

Pores regular, circular, of equal size, hexagonally framed, of the same breadth as the bars. Radial bristles twice as long as the diameter of one pore. Mouth with five to six parallel, conical strong teeth, which are twice as long as a bristle (fig. 6a).

Dimensions.—Diameter of the shell 0.5 to 0.7, of the pores 0.02 to 0.03.

Habitat.—North Pacific, Stations 252 to 256, surface.

2. Castanella thomsoni, n. sp.

Pores regular, circular, of equal size, hexagonally framed, twice as broad as the bars. Radial bristles about as long as the diameter of one pore. Mouth with four strong, conical teeth, forming a regular cross, four times as long as a bristle.

Dimensions.—Diameter of the shell 0.7 to 0.8, of the pores 0.03.

Habitat.—South Pacific, Stations 295 to 298, surface.

3. Castanella campbelli, n. sp.

Pores regular, circular, hexagonally framed, three times as broad as the bars. Radial bristles half as long as the radius of the shell. Mouth with a coronet of eight conical, parallel teeth, of the same length as the bristles, but four to six times as thick.

Dimensions.—Diameter of the shell 0.4 to 0.45, of the pores 0.025.

Habitat.—Central Pacific, Stations 270 to 274, surface.

4. Castanella sloggetti, n. sp.

Pores subregular, circular, without frames, of different sizes, about twice as broad as the bars. Radial bristles three times as long as one pore. Mouth with five or six strong, conical teeth, twice as long as the bristles.

Dimensions.—Diameter of the shell 0.3 to 0.36, of the pores 0.02 to 0.03.

Habitat.—Tropical Atlantic, Stations 347 to 349, surface.

5. Castanella balfouri, n. sp.

Pores irregular, roundish, two to three times as broad as the bars. Bristles about one-fourth as long as the radius. Mouth with four strong conical teeth, forming a cross, somewhat longer and much thicker than the bristles.

Dimensions.—Diameter of the shell 0.22 to 0.28, of the pores 0.01 to 0.02.

Habitat.—North Pacific, Stations 240 to 245, surface.

6. Castanella channeri, n. sp.

Pores irregular, roundish, two to four times as broad as the bars. Bristles nearly half as long as the radius. Mouth with seven to nine short conical teeth, shorter than the bristles, but much thicker.

Dimensions.—Diameter of the shell 0.3 to 0.4, of the pores 0.02 to 0.025.

Habitat.—North Atlantic, Stations 352 to 354, surface.

7. Castanella horstoni, n. sp.

Pores irregular, polygonal, three to four times as broad as the bars. Bristles about as long as the radius. Mouth with six stout pyramidal teeth, which are scarcely one-third as long as the radius.

Dimensions.—Diameter of the shell 0.55, of the pores 0.02 to 0.025.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Genus 707. Castanidium,^[324] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Castanellida, with simple radial main-spines and a simple smooth mouth.

The genus Castanidium agrees with its ancestral form Castanarium in the simple shape of the smooth and toothless mouth, but differs from it in the possession of long radial main-spines, which are scattered between the constant radial bristles or by-spines of the surface. The shell agrees therefore in its general shape with the Astrosphæride Heliosphæra, as defined above (p. 217, Pl. 26, fig. 9), but differs from it in the possession of the shell-mouth wanting in all Sphæroidea.

1. Castanidium willemoesi, n. sp.

Pores regular, circular, hexagonally framed, twice as broad as the bars. Bristles three times as long as the diameter of one pore. Radial main-spines straight, conical, smooth, as long as the radius.

Dimensions.—Diameter of the shell 0.3 to 0.4, of the pores 0.012 to 0.016.

Habitat.—Central Pacific, Station 263 to 274, surface.

2. Castanidium wildi, n. sp.

Pores regular, circular, hexagonally framed, of the same breadth as the bars. Bristles twice as long as one pore. Radial main-spines straight and short, cylindrical, with dimpled surface (as in Pl. 113, fig. 1), as broad as one pore and as long as the diameter of the shell.

Dimensions.—Diameter of the shell 0.66, of the pores 0.045.

Habitat.—South Pacific, Station 297, surface.

3. Castanidium buchanani, n. sp. (Pl. 113, fig. 7).

Pores regular, circular, without frames, twice as broad as the bars, of variable size. Bristles five to six times as long as one pore. Radial main-spines numerous, straight, slender, cylindrical, about as long as the diameter of the shell.

Dimensions.—Diameter of the shell 0.25 to 0.3, of the pores 0.012 to 0.02.

Habitat.—Tropical Atlantic, Stations 346 to 349, surface.

4. Castanidium murrayi, n. sp. (Pl. 113, figs. 5, 5a).

Pores subregular, circular, without frames, three times as broad as the bars. Bristles three times as long as one pore. Radial main-spines cylindrical, stout, irregularly curved, longer than the shell-diameter, covered with longish hexagonal dimples, which are separated by a network of prominent crests (fig. 5a).

Dimensions.—Diameter of the shell 0.4 to 0.5, of the pores 0.02 to 0.025.

Habitat.—North Atlantic, Station 352 to 354, surface.

5. Castanidium aldrichi, n. sp.

Pores subregular, circular, without frames, of variable size, about as broad as the bars. Bristles four times as long as one pore. Radial main-spines conico-cylindrical, irregularly curved, straight, about as long as the radius. (The conical base of the spines is inflated and fenestrated, therefore the shell is nearly polyhedral.)

Dimensions.—Diameter of the shell 0.35 to 0.4, of the pores 0.012 to 0.015.

Habitat.—Central Pacific, Stations 270 to 274, surface.

6. Castanidium bromleyi, n. sp.

Pores irregular, roundish, two to four times as broad as the bars. Bristles half as long as the radius. Radial main-spines cylindrical, straight, slender, longer than the shell-diameter.

Dimensions.—Diameter of the shell 0.22 to 0.26, of the pores 0.006 to 0.02.

Habitat.—Indian Ocean and Southern Pacific, Stations 162 to 169, surface.

7. Castanidium bethelli, n. sp.

Pores irregular, roundish or polygonal, two to three times as broad as the bars. Bristles one-third as long as the radius. Radial main-spines conico-cylindrical, irregularly curved, with dimpled surface, somewhat longer than the radius.

Dimensions.—Diameter of the shell 0.5 to 0.6, of the pores 0.015 to 0.03.

Habitat.—North Pacific, Stations 235 to 245, surface.

8. Castanidium moseleyi, n. sp. (Pl. 113, fig. 2).

Pores irregular, roundish or polygonal, two to four times as broad as the bars. Bristles about as long as the diameter of one pore, or a little longer. Radial main-spines cylindrical, irregularly curved, somewhat longer than the diameter of the shell; their base is more or less inflated and fenestrated, therefore the shell is nearly polyhedral.

Dimensions.—Diameter of the shell 0.7 to 0.8, of the pores 0.01 to 0.04.

Habitat.—Tropical Atlantic, Stations 346 to 349, surface.

Genus 708. Castanissa,^[325] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Castanellida with simple radial main-spines and a dentate mouth.

The genus Castanissa agrees with the preceding Castanidium in the possession of large radial main-spines, scattered between the numerous bristles or by-spines of the surface; but it differs from it in the possession of teeth around the mouth, identical with those of Castanella; it may be derived therefore either from the latter by development of main-spines, or from the former by formation of teeth.

1. Castanissa challengeri, n. sp. (Pl. 113, fig. 1).

Pores regular, circular, three times as broad as the bars. Bristles one-fourth as long as the radius. Radial main-spines (about twelve) very stout, straight, cylindrical, at the distal end conical, pointed, with dimpled surface, about half as long as the radius. Mouth very large, circular, about one-third as broad as the shell, with a corona of twelve to sixteen very large, triangular, parallel teeth.

Dimensions.—Diameter of the shell 0.7 to 0.8, of the pores 0.03.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

2. Castanissa pearceyi, n. sp.

Pores regular, circular, twice as broad as the bars. Bristles half as long as the radius. Radial main-spines (about twenty) slender, cylindrical, smooth, irregularly curved, about as long as the radius. Mouth large, half as broad as the radius, with a corona of ten to twelve irregular, slender teeth.

Dimensions.—Diameter of the shell 0.5 to 0.6, of the pores 0.02.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

3. Castanissa richardsi, n. sp.

Pores subregular, circular, about as broad as the bars. Bristles twice as long as one pore. Radial main-spines (about twenty) slender, cylindrical, irregularly curved, with dimpled surface (like those in Pl. 113, fig. 5a). Mouth with a corona of six stout, parallel, triangular teeth.

Dimensions.—Diameter of the shell 0.3 to 0.35, of the pores 0.015.

Habitat.—North Atlantic, Station 354, surface.

4. Castanissa crosbiei, n. sp.

Pores irregular, roundish, two to three times as broad as the bars. Bristles one-third as long as the radius. Radial main-spines very numerous, straight, cylindrical, smooth, about as long as the diameter of the shell. Mouth with ten or twelve irregular, conical, parallel teeth.

Dimensions.—Diameter of the shell 0.28, of the pores 0.01 to 0.015.

Habitat.—North Pacific, Stations 231 to 235, surface.

5. Castanissa macleani, n. sp.

Pores irregular, roundish or polygonal, two to four times as broad as the bars. Bristles about one-fourth as long as the radius. Radial main-spines numerous, straight, conical, stout, with dimpled surface, shorter than the radius. Mouth with six to eight irregular conical teeth.

Dimensions.—Diameter of the shell 0.32, of the pores 0.012 to 0.024.

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

6. Castanissa hoylei, n. sp.

Pores irregular, polygonal, two to three times as broad as the bars. Bristles nearly half as long as the radius. Radial main-spines (about thirty) very long and thin, cylindrical, irregularly curved, at the conical base inflated and fenestrated; shell therefore slightly polyhedral. Mouth with five strong conical teeth.

Dimensions.—Diameter of the shell 0.35 to 0.4, of the pores 0.02 to 0.03.

Habitat.—North Pacific, Station 245 to 250, surface.

Genus 709. Castanopsis,^[326] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Castanellida with branched radial main-spines and a simple smooth mouth.

The genus Castanopsis differs from its ancestral form Castanidium in the ramification of the radial main-spines; the branches are usually very irregular and often partly confluent. The shell is very similar to the Astrosphæride Cladococcus (compare above p. 223, Pl. 27), but differs from it in the possession of the shell-mouth, absent in all Sphæroidea.

1. Castanopsis naresi, n. sp. (Pl. 113, fig. 3).

Pores subregular, circular, about twice as broad as the bars. Bristles twice as long as one pore. Radial main-spines somewhat shorter than the diameter of the shell, straight, cylindrical, in the proximal half simple, in the distal half irregularly branched, each with ten to twelve partly confluent branches.

Dimensions.—Diameter of the shell 0.6 to 0.7, of the pores 0.02 to 0.03.

Habitat.—Tropical Atlantic, Station 347 to 349, surface.

2. Castanopsis macleari, n. sp.

Pores irregular, roundish, two to four times as broad as bars. Bristles half as long as the radius. Radial main-spines about as long as the radius, stout and straight, cylindrical, forked at the distal end, with two or three unequal fork-branches.

Dimensions.—Diameter of the shell 0.42, of the pores 0.015 to 0.03.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

3. Castanopsis fergusoni, n. sp.

Pores irregular, roundish or polygonal, about as broad as the bars. Bristles three times as long as one pore. Radial main-spines somewhat longer than the diameter of the shell, cylindrical, with irregular and partly confluent lateral branches (similar to Pl. 113, fig. 4a).

Dimensions.—Diameter of the shell 0.55, of the pores 0.012 to 0.016.

Habitat.—North Atlantic, Station 354, surface.

Genus 710. Castanura,^[327] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Castanellida with branched radial main-spines and a dentate mouth.

The genus Castanura differs from the preceding Castanopsis in the possession of a corona of teeth surrounding the mouth, similar to that of Castanissa. It differs from the latter in the ramification of the radial main-spines, wherein it agrees with the former. Castanura may therefore be derived either from Castanissa by ramification of the main-spines, or from Castanopsis by development of teeth around the mouth.

1. Castanura tizardi, n. sp. (Pl. 113, fig. 4, 4a).

Pores regular, circular, without hexagonal frames, twice as broad as the bars. Bristles twice as long as one pore. Radial main-spines somewhat longer than the radius, straight, very stout, with irregular lateral branches, which are partly confluent. Mouth with six strong conical teeth.

Dimensions.—Diameter of the shell 0.6, of the pores 0.03.

Habitat.—Tropical Atlantic, Station 346, surface.

2. Castanura havergali, n. sp.

Pores regular, circular, hexagonally framed, as broad as the bars. Bristles three times as long as one pore. Radial main-spines as long as the shell-diameter, in the basal half simple, in the distal half with irregular, not confluent, lateral branches. Mouth with ten to twelve irregular, parallel, conical teeth of different sizes.

Dimensions.—Diameter of the shell 0.5, of the pores 0.045.

Habitat.—Indian Ocean, Madagascar (Rabbe), surface.

3. Castanura swirei, n. sp.

Pores regular, circular, hexagonally framed, as broad as the bars. Bristles half as long as the radius. Radial main-spines straight, longer than the shell-diameter; on the distal end with a few irregular, confluent, lateral branches. Mouth with six larger and six alternate smaller, parallel, conical teeth.

Dimensions.—Diameter of the shell 0.28, of the pores 0.015.

Habitat.—North Pacific, Station 253, surface.

4. Castanura carpenteri, n. sp.

Pores irregular, roundish, twice to four times as broad as the bars. Bristles about as long as the largest pores. Radial main-spines irregularly curved, longer than the shell-diameter, with inflated and fenestrated conical base; in the distal half irregularly branched, with simple, not confluent, lateral branches. Mouth with six to nine irregular, strong, conical teeth.

Dimensions.—Diameter of the shell 0.3, of the pores 0.012 to 0.025.

Habitat.—South Atlantic, Station 331, depth 1715 fathoms.

Family LXXXI. Circoporida, Haeckel, 1879 (Pls. 114-117).

Definition.—Phæodaria with a spherical or polyhedral shell, exhibiting a peculiar solid porcellanous structure, with a stellate circle of radial pores around the base of the hollow radial spines. Mouth usually with teeth. Surface of the shell tabulate, panelled or dimpled. Central capsule excentric, placed in the aboral half of the shell-cavity.

The family Circoporida comprises those Phæodaria in which the simple spherical or polyhedral shell exhibits a peculiar porcellanous structure, possesses a simple mouth, and is particularly distinguished by the constant character denoted by their name, viz., by circles of pores surrounding the base of the radial spines. It agrees in these striking peculiarities with the following family, the Tuscarorida, but differs from them essentially by the spherical or polyhedral form of the shell, which is never ovate, with the main axis prolonged. The radial spines, variable in number, are regularly or symmetrically disposed in all Circoporida, whilst they are arranged around the poles of the main axis in all Tuscarorida. Whilst the latter are always extremely large, more than a millimeter in size, the former are much smaller and never reach the diameter of a millimeter. The number of genera and species in this family is not large, and the majority are very rare, but they belong to the most remarkable Radiolaria by the peculiar structure, as well as by the geometrical regularity of the polyhedral shell.

The Circoporida may be divided into two different subfamilies, the Circogonida and the Haeckelinida. The latter are represented by the single genus Haeckeliana (Pl. 114), and possess a spherical shell with numerous small dimples between the circles of pores, and numerous simple radial spines which do not exhibit a regular arrangement. The Circogonida, on the other hand, comprise all other genera (Pls. 115-117) and possess a panelled shell with polygonal plates, and a certain number of radial spines, which are regularly disposed on the corners of the polyhedral shell, and usually armed with verticillate bristles and terminal forks or spathillæ. Perhaps the Circogonida and Haeckelinida may be better considered as two separate families.

The geometrical fundamental form of the shell is in the Circoporida of the highest interest, since it exhibits regular proportions, which are very rare in other organic forms, generally some rare forms of regular polyhedrons. The shell in all members of this family belongs to that group of geometrical forms which I have called in my General Morphology "Polyaxonia" (vol. i., 1866, pp. 406-416). The shell therefore is constantly an "endospherical polyhedron," i.e., a polyhedron, all the corners of which lie in a spherical surface. The corners are always indicated by the bases of the radial spines arising from the surface of the shell and marking its axes, and it is immaterial whether the shell itself is a true polyhedron or a sphere; for in the latter case also the radial spines mark the axes of the polyhedron.

The six genera which we here distinguish among the Circoporida, represent six different fundamental forms. Circoporus (Pl. 115, figs. 1-3; Pl. 117, figs. 5, 6) possesses six radial spines, opposite in pairs in three diameters, perpendicular one to another; it agrees therefore with the Cubosphærida (p. 169, Pls. 21-25) and represents the regular octahedron, with eight congruent triangular faces and six corners. It has the same form as the well-known antheridia of Chara (Gener. Morphol., vol. i. p. 412). Circogonia (Pl. 115, figs. 8-10; Pl. 117, fig. 1) exhibits twelve radial spines, opposite in pairs in six equidistant diameters. The surface of the shell is divided into twenty equal and equilateral triangles, and agrees therefore with the regular icosahedron. The same form appears also in some forms of Aulosphæra, and in several Astrosphærida (Gener. Morphol., vol. i. p. 411). Circorrhegma (Pl. 117, fig. 2) possesses a regular shell with twelve equal pentagonal faces and twenty equidistant corners, from which arise twenty regularly disposed radial spines. It represents therefore the regular "pentagonal dodecahedron," the same remarkable form which is found in some Astrosphærida, and in the pollen-grains of some plants, e.g., Bucholzia maritima, Fumaria spicata, Polygonum amphibium, &c. (Gener. Morphol., vol. i. p. 412, Taf. ii. fig. 18).

The three genera of Circoporida mentioned therefore represent three different forms of regular polyhedrons, in the exact mathematical sense, viz., Circoporus, the regular octahedron, Circogonia, the regular icosahedron, and Circorrhegma, the regular dodecahedron. In each of these three regular forms all the faces, edges, and corners are equal. The remaining three genera of Circoporida represent, however, three forms of subregular or irregular endospherical polyhedra, which are not perfectly regular. Circospathis (Pl. 115, figs. 4-7; Pl. 117, fig. 3) is a rather common form, and constantly possesses nine symmetrically disposed radial spines; the shell is either spherical or polyhedral, with fourteen triangular faces and thirty edges; the nine spines lie in three meridional planes, which are crossed at equal angles (three equidistant spines in each plane). We call this remarkable form the tetradecahedron; it appears also in some Astrosphærida (e.g., in Haliomma echinaster, figured in my Monograph, Taf. xxiv. fig. 1). Circostephanus (Pl. 116, fig. 3) exhibits a subregular polyhedral shell with a variable number of triangular faces and of radial spines (twenty-four to forty or more). Circostephanus sexagenarius possesses sixty triangular equilateral faces, which are disposed in twelve pentagonal groups (each with five faces), so that the shell seems to be derived from a regular pentagonal dodecahedron, the twelve regular faces of which are divided each into five congruent triangles. From its corners arise thirty-two radial spines (twelve from the central points of the pentagons, twenty from the meeting corners of every three pentagons). In other cases the number of faces and radial spines seems to be larger and their arrangement more irregular. The same may be said of Haeckeliana, in which the dimpled shell is constantly spherical, and possesses a variable number of radial spines, from sixteen to fifty-five (usually between thirty and forty).

The structure of the shell in the Circoporida is the same as in the Tuscarorida, of a peculiar porcellanous nature. The shell-wall is very thick, more or less opaque, and in direct light whitish or yellowish. Its surface is dimpled, with numerous small, circular, roundish or polygonal dimples in Haeckeliana (Pl. 114, figs. 1-6). In the Circogonida, however, the surface is panelled, with regular or irregular polygonal plates, often separated by high prominent crests (Pl. 115, figs. 4-9, &c.). Numerous simple thin needles of silica lie tangentially disposed and irregularly scattered in the porcellanous or cement-like substance of the thick shell-wall. Under a strong lens this substance appears finely punctate, being probably pierced by numerous very fine pores. The surface of the shell is therefore minutely roughened, and often appears quite black under the microscope, by the adhesion of innumerable fine air-bubbles. In all Circoporida, as well is in the Tuscarorida, the porcellanous shell has not the perfect transparency of the purely siliceous shells of other Radiolaria; its refractive power is somewhat different from the latter; it becomes deeply stained by carmine and browned by fire, and seems therefore to consist of a peculiar carbonic silicate.

The shell in all Circoporida exhibits a simple, excentric mouth, which corresponds to the main osculum of the central capsule. The excentric position of this shell-mouth has no influence on the regular form of the shell. The mouth is either circular or polygonal, usually about as large as a basal circle of pores. It is always armed with prominent conical or pyramidal teeth, the number of which is variable and seems to depend partly upon the number of the shell-faces or the radial spines. Circoporus has usually four cruciate teeth (Pl. 115, fig. 1; Pl. 117, figs. 4, 5). Circorrhegma exhibits a pentagonal mouth with five teeth (Pl. 117, fig. 2). Circogonia possesses a hexagonal mouth with six teeth (Pl. 115, fig. 8; Pl. 117, fig. 1). Circospathis has no constant number; some species have five teeth (Pl. 115, fig. 4), others four (Pl. 115, fig. 10), others nine (Pl. 117, fig. 3a). Circostephanus is also variable; one species exhibits eight teeth (Pl. 116, fig. 3a), another ten, another twelve. In Haeckeliana (Pl. 114, fig. 3) the teeth are smaller and more numerous. Usually the teeth arise vertically from the surface of the shell and are spinulate; more rarely their points are directed towards the centre of the mouth. Sometimes numerous thin needles arise between the teeth (Pl. 115, fig. 10).

The radial spines of the Circoporida are tubular, usually cylindrical and conical at the thickened base, more rarely prismatic or slenderly pyramidal, with three or more edges; sometimes the edges are spirally wound around the axis (Pl. 115, fig. 6). In the majority of species their length is about equal to the diameter of the shell; often they are somewhat shorter, more rarely longer. Their tubular structure is always the same as in the Tuscarorida; the wall of the tube is thick, and in the axis of its cavity lies an axial cord or funicle, which is connected with the wall by numerous horizontal, simple, or branched threads (Pl. 115, figs. 6, 7). The axial funicle itself is either a simple thread of silica, or a strand, composed of three to fifteen or more filaments, which are closely twisted like a rope around the axis of the spine, and arise separately from the bridges between the pores of the basal circle (Pl. 115, figs. 7, 9). The number of pores in these circles is very variable, commonly from three to nine, sometimes twelve to fifteen or more; their form is usually irregularly ovate (Pl. 115, figs. 7, 9). The bridges between the pores usually bear numerous siliceous threads or bristles, which are curved downwards or upwards (Pl. 115, figs. 4-6). Sometimes the spines are entirely covered with similar bristles or cilia (Pl. 117, figs. 2-5), more rarely with regular verticils of lateral branches (Pl. 117, fig. 6).

The distal ends of the radial spines are simple in Haeckeliana (Pl. 114), whilst in the other Circoporida they are usually (or perhaps constantly) either forked or armed with a verticil of terminal branches. When the spines are simply forked, their two terminal branches lie in certain meridional planes (Pl. 117, fig. 5). The same is probably the case when they bear three divergent branches (Pl. 115, figs. 1, 2), or four crossed branches (Pl. 117, figs. 4, 6). The larger species usually bear a corona of five curved branches disposed around the distal apex of each spine (Pl. 116, fig. 3; Pl. 117, figs. 1, 2). Sometimes the formation of these coronas is twice or more often repeated, so that the spines appear verticillate.

The central capsule of the Circoporida (Pl. 115, fig. 8; Pl. 117, fig. 6) is usually about half as large as the enclosing shell, and lies excentrically in that half of its cavity which is remote from the shell-mouth (Pl. 115, fig. 8). The other half (near the mouth) is filled up by the cap-shaped, dark phæodium. The proboscis, or the central tubule of the astropyle, is hidden in the axis of the blackish phæodium, and is directed towards the mouth of the shell; it is often S-shaped, more or less curved. The circular radiate operculum of the astropyle, placed on the base of the proboscis, exhibits numerous branched radial ribs, and closes the main-opening like the lid of a tea-kettle (Pl. 115, fig. 3). The number of the parapylæ, or the accessory openings of the capsule, which in the majority of Phæodaria is two, seems to be usually increased in the Circoporida. In Circoporus the capsule seems to posses six and in Circospathis nine secondary openings, and therefore there is some probability that each circle of pores on the base of a radial spine corresponds to a secondary opening of the capsule. In Haeckeliana, however (Pl. 114), I could observe no parapylæ at all. These accessory openings are always very small in the Circoporida, and may be easily overlooked. Furthermore, the number of observations respecting this difficult point is too small, and their certainty not satisfactory; it requires therefore further accurate examination, as also does the whole central capsule of the Circoporida.

The numerous and remarkable characters of shape and structure, which we have described above as occurring in the Circoporida, are also found in the following closely allied family, the Tuscarorida; all the species are inhabitants of great depths. Perhaps it may therefore be more convenient to separate these two families from the other Phæogromia as a peculiar order, under the name Phæocalpia.

Synopsis of the Genera of Circoporida.

I. Subfamily Circogonida. Shell spherical or polyhedral with panelled structure and polygonal plates. A certain number of radial spines are geometrically disposed. Shell octahedral (or spherical), Six radial spines, 711. Circoporus.

Shell tetradecahedral, Nine radial spines, 712. Circospathis.

Shell icosahedral, Twelve radial spines, 713. Circogonia.

Shell dodecahedral, Twenty radial spines, 714. Circorrhegma.

Shell polyhedral, Twenty-four to forty or more radial spines, 715. Circostephanus.

II. Subfamily Haeckelinida. Shell spherical, with dimpled structure, and a variable number of radial spines (without polygonal plates), 716. Haeckeliana.

I. Subfamily Circogonida. Shell spherical or polyhedral with panelled structure and polygonal plates. A certain number of radial spines are geometrically disposed.

Shell octahedral (or spherical),

Six radial spines,

711. Circoporus.

Shell tetradecahedral,

Nine radial spines,

712. Circospathis.

Shell icosahedral,

Twelve radial spines,

713. Circogonia.

Shell dodecahedral,

Twenty radial spines,

714. Circorrhegma.

Shell polyhedral,

Twenty-four to forty or more radial spines,

715. Circostephanus.

II. Subfamily Haeckelinida.

Shell spherical, with dimpled structure, and a variable number of radial spines (without polygonal plates),

716. Haeckeliana.

Subfamily 1. Circogonida, Haeckel.

Definition.—Circoporida with panelled shell, composed of polygonal plates. The shell is usually polyhedral, more rarely spherical, and the radial spines are usually (or perhaps constantly) branched and regularly arranged.

Genus 711. Circoporus,^[328] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Circoporida with a spherical or regularly octahedral shell, composed of eight congruent, triangular plates, with six corners from which arise six radial spines, opposite in pairs in three diameters, perpendicular one to another.

The genus Circoporus, the simplest among the Circoporida, is distinguished by the regular octahedral form of the shell, with the three equal axes of the regular crystalline system perpendicular one to another. Six equal radial spines, arising from the six corners, lie opposite in pairs in those three dimensive axes. The eight equal triangular faces of the octahedron are sometimes plane, sometimes concave or convex, and sometimes the shell becomes spherical. In this case it becomes very similar to the Hexastylida among the Sphæroidea.

1. Circoporus sexfurcus, Haeckel (Pl. 117, fig. 5).

Challengeria sp., John Murray, 1876, Proc. Roy. Soc. Lond., vol. xxiv. pl. xxiv. fig. 5.

Shell spherical, covered with irregular, polygonal plates. Six radial spines shorter than the diameter of the shell, covered with thin curved bristles, in the proximal half cylindrical, in the distal half forked, each with two equal curved fork-branches. Around the ciliated base of each spine a corona of twelve to sixteen pores surrounded by a circle of numerous, curved, longer bristles. Mouth cruciform, with four triangular, convergent teeth.

Dimensions.—Diameter of the shell 0.55, length of the spines 0.4.

Habitat.—South Pacific, Station 289, depth 2550 fathoms.

2. Circoporus hexastylus, n. sp. (Pl. 117, fig. 4).

Shell regularly octahedral, with eight plane, congruent, triangular faces, which are covered with a very delicate network of small, regular, hexagonal plates. Six radial spines as long as the radius of the shell, four-sided pyramidal, simple, in the basal half covered with numerous curved bristles. Around the base of each spine a corona of four equal pores, surrounded by a circle of twelve short teeth. Apex with four crossed, curved branches (like those of Circospathis tetrodon). Mouth cruciform, with four smooth teeth.

Dimensions.—Diameter of the shell 0.24, length of the spines 0.12.

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

3. Circoporus characeus, n. sp.

Shell spherical, covered with a delicate network of irregular polygonal plates. Six radial spines longer than the diameter of the shell, cylindrical, covered with numerous curved bristles, each with eight pores at the base surrounded by a circle of long bristles. Apex of each spine with a trident or fuscina, similar to that of the following species. Similar to an antheridium of Chara.

Dimensions.—Diameter of the shell 0.32, length of the spines 0.4.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

4. Circoporus sexfuscinus, n. sp. (Pl. 115, figs. 1-3).

Shell subregular, octahedral, with eight triangular, concave, somewhat unequal faces, which are covered with an extremely delicate network of small square dimples, and furrowed by radial crests arising from the bases of the spines (fig. 2). Six radial spines about as long as the diameter of the shell, four-sided, prismatic, with rounded edges; each in the basal half with a verticil of four crossed, curved bristles (fig. 1), sometimes with two verticils (fig. 2); on the distal apex inflated, armed with a trident or fuscina. Around the base of each spine four crossed elliptical pores. Mouth cruciform, with four small teeth (fig. 1).

Dimensions.—Diameter of the shell 0.2 to 0.25, length of the spines 0.2 to 0.25.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

5. Circoporus octahedrus, n. sp. (Pl. 117, fig. 6).

Shell regularly octahedral, with eight plane, or slightly convex, congruent, triangular faces, which are covered with very small, regular, triangular plates (like those of Polypetta tabulata, Pl. 116, fig. 2). Six stout radial spines, about as long as the diameter of the shell, four-sided prismatic, covered with three or four verticils of four long curved bristles; at the distal apex inflated, with four crossed, divergent, stout, curved horns. Around the pyramidal base of each spine a corona of eight pores (two on each of the four faces). Mouth cruciform, with four triangular, convergent teeth.

Dimensions.—Diameter of the shell 0.16, length of the spines 0.18.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

Genus 712. Circospathis,^[329] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Circoporida with a subregular, spherical, or polyhedral shell, composed of fourteen triangular, nearly equal plates, with nine corners, from, which arise nine radial spines, symmetrically disposed.

The genus Circospathis exhibits the remarkable and peculiar form of a "Tetradecahedron," or a subregular polyhedron with fourteen triangular faces, thirty edges, and nine corners, from which arise nine radial spines. These lie in three meridional planes, which are crossed at equal angles (three equidistant spines in each plane). The same interesting form occurs also in some Astrosphærida, which bear nine regularly disposed radial spines, as Haliomma echinaster. All four observed species of Circospathis are South Atlantic.

1. Circospathis furcata, n. sp. (Pl. 115, figs. 4-6).

Shell polyhedral or nearly spherical, with nine prominent corners, from which arise nine radial spines, about as long as the diameter of the shell. The polygonal plates of the shell are separated by high crests, usually hexagonal or pentagonal, irregular, about twelve to fifteen on the half meridian. Radial spines cylindrical, straight, about as long as the diameter of the shell, with spirally turned edges, covered with numerous curved bristles, at the distal end forked; the two fork branches curved, one-third as long as the simple basal part. The inflated base of each spine is surrounded by a corona of nine to twelve ovate basal pores. Mouth pentagonal, with five thick, mammillate and spinulate, somewhat convergent teeth (fig. 5).

Dimensions.—Diameter of the shell 0.6, length of the spines 0.5.

Habitat.—South Atlantic (east of Buenos Ayres), Station 325, depth 2650 fathoms.

2. Circospathis novena, n. sp. (Pl. 117, figs. 3, 3a).

Shell polyhedral (tetradecahedral), with fourteen triangular, plane, or slightly convex faces, covered with small, irregular, polygonal (usually hexagonal) plates, and nine prominent corners, from which arise nine radial spines, shorter than the diameter of the shell. Each spine is surrounded at the broader base by a circle of twelve to sixteen pores and a corona of bristles, and bears at the inflated distal apex a trident or fuscina, similar to that of Circoporus sexfuscinus (Pl. 115, fig. 2). Mouth with nine convergent, conical, denticulate teeth (fig. 3a).

Dimensions.—Diameter of the shell 0.6, length of the spines 0.4.

Habitat.—South Atlantic, Station 318 (east of Patagonia), depth 2040 fathoms.

3. Circospathis tetradeca, n. sp.

Shell spherical, covered with irregular, polygonal plates. Nine radial spines, cylindrical, as long as the radius of the shell, bristly, armed at the distal apex with a trident. (In one specimen six spines possessed three terminal branches, two spines two branches, and one spine four branches.) The broader base of each spine is surrounded by a corona of nine pores and a circle of curved bristles. Mouth with nine smooth conical teeth.

Dimensions.—Diameter of the shell 0.55, length of the spines 0.3.

Habitat.—South Atlantic, Station 332 (west of Tristan da Cunha), depth 2200 fathoms.

4. Circospathis tetrodonta, n. sp. (Pl. 115, fig. 10).

Shell subspherical or polyhedral, with fourteen triangular, convex faces, covered with irregular polygonal plates. Nine radial spines cylindrical, nearly smooth, about as long as the diameter of the shell; at the distal apex with four strong curved horns, like those of Circoporus hexastylus, Pl. 117, fig. 4. Each spine is surrounded at the base by a corona of nine irregular pores. Mouth with four large, prominent, conical teeth, which are spinulate, with vertical inner edge (fig. 10).

Dimensions.—Diameter of the shell 0.5, length of the spines 0.45.

Habitat.—South Atlantic, Station 323 (east of Buenos Ayres), depth 1900 fathoms.

Genus 713. Circogonia,^[330] n. gen.

Definition.—Circoporida with a regular icosahedral shell, composed of twenty congruent, triangular plates, with twelve corners, from which arise twelve radial spines.

The genus Circogonia is remarkable for the regular icosahedral form of its shell, a geometrical fundamental form, which occurs very rarely in organised bodies (as in Aulacantha icosahedra, and in some Astrosphærida with twelve regularly disposed radial spines). The shell is composed of twenty triangular, equilateral and congruent plates, which are sometimes separated by prominent crests; their surface is panelled by smaller hexagonal or polygonal secondary plates. The thirty edges between the plates are sometimes thickened. From the twelve corners of the regular icosahedron (where every five triangular plates meet), twelve equal radial spines arise, each of which is surrounded at the base by a corona of nine to sixteen pores. Two species only of Circogonia have been observed; the one has smooth spines, forked at the distal end, the other bears numerous curved bristles around each spine, and at the distal end a verticil of five curved branches. The mouth of the shell (placed in the centre of one of the triangular plates) is in both species armed with six teeth. Both species are found in the Tropical Atlantic.

1. Circogonia icosahedra, n. sp. (Pl. 117, figs. 1, 1a).

Shell regularly icosahedral, with twenty equal, triangular, nearly plane faces, which are separated by thirty prominent, crest-like edges, and covered by a delicate network of small, subregular, hexagonal plates. Twelve radial spines nearly conical, one and a half times as long as the radius of the shell, with five prominent edges. The campanulate base of each spine is covered with numerous long, curved bristles, surrounded by a circle of twelve to sixteen ovate, irregular pores, and separated from the slender distal part by a constriction. The distal apex of the spine is surrounded by a verticil of five conical, curved branches (corresponding to the five edges of the spines, and to the five faces, which meet in the corners where the spine arises). Mouth hexagonal, with six conical, spinulate teeth, convergent towards its centre (fig. 1a).

Dimensions.—Diameter of the shell 0.75, length of the spines 0.5.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

2. Circogonia dodecacantha, n. sp. (Pl. 115, figs. 8, 9).

Shell subregularly icosahedral, with twenty equal, triangular, slightly convex faces, which are not separated by prominent crests, but covered with a network of irregular polygonal plates. Twelve radial spines, cylindrical, smooth, about as long as the diameter of the shell, forked at the distal end with two divergent, slightly curved branches (similar to Circospathis furcata, Pl. 115, figs. 4-6). The conical base of each spine is surrounded by a circle of nine to twelve irregular, ovate pores (fig. 9). Mouth circular, with a corona of six conical, smooth teeth which arise perpendicularly from the shell (in the upper part of fig. 8, at left).

Dimensions.—Diameter of the shell 0.6, length of the spines 0.7.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

Genus 714. Circorrhegma,^[331] n. gen.

Definition.—Circoporida with a regular dodecahedral shell, composed of twelve congruent, pentagonal plates, with twenty corners, from which arise twenty radial spines.

The genus Circorrhegma is remarkable for the geometrical regularity of its shell, which represents a pentagonal dodecahedron. The shell is therefore composed of twelve equal and regular pentagonal plates, and these are separated in the only known species by thirty prominent crest-like edges. From the corners of the dodecahedron, at which every three pentagons meet, arise twenty radial spines, opposite in pairs in ten equidistant axes.

1. Circorrhegma dodecahedra, n. sp. (Pl. 117, figs. 2, 2a).

Shell dodecahedral, with twelve equal and regular, plane, pentagonal plates, which are separated by thirty prominent crests, and bear a network of numerous polygonal (usually also pentagonal), smaller plates. Twenty radial spines about as long as the radius of the shell, three-sided prismatic, covered with numerous bristles; each surrounded at the thickened base by a circle of twelve to sixteen pores, and at the distal apex by a corona of five curved, terminal branches. Mouth pentagonal, with five conical, subvertical, spinulate teeth (fig. 2a).

Dimensions.—Diameter of the shell 0.8, length of the spines 0.5.

Habitat.—Indian Ocean, Madagascar (Rabbe).

Genus 715. Circostephanus,^[332] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Circoporida with a subregular, polyhedral or nearly spherical shell, composed of thirty to sixty or more triangular plates, with twenty-four to thirty-two or more corners, from which arise radial spines, symmetrically disposed.

The genus Circostephanus comprises those Circoporida in which the porcellanous shell is an endospherical polyhedron, with numerous (thirty to sixty or more) triangular faces, and has a variable number of radial spines (twenty-four to forty or more), arising from its corners. The number of faces and corners seems to be variable in this genus, but may perhaps be typical in some species. Circostephanus sexagenarius has the typical form of a "Sexagenal-Polyhedron," with sixty equal triangular faces and thirty-two corners, and may be derived from the "Pentagonal-Dodecahedron" (Circorrhegma) by dividing its twelve pentagonal faces each into five congruent triangles.

1. Circostephanus coronarius, n. sp. (Pl. 116, figs. 3, 3a, 3b).

Shell polyhedral, with thirty-two to forty triangular, concave faces of nearly equal size, which are separated by high prominent crests. From the elevated corners of the polyhedron arise twenty-four to thirty radial spines, which are three-sided prismatic or nearly cylindrical, about as long as the radius of the shell, and covered with long curved bristles. The distal end of each spine is surrounded by a verticil of five stout, curved branches, its pyramidal base by a corona of five (or sometimes six) ovate, basal pores (fig. 3b). Mouth armed with a corona of eight short, conical, vertical, spinulate teeth (fig. 3a).

Dimensions.—Diameter of the shell 0.4 to 0.5, length of the spines 0.2 to 0.25.

Habitat.—South-Eastern Pacific (off Valparaiso), Station 298, depth 2225 fathoms.

2. Circostephanus sexagenarius, n. sp.

Shell polyhedral, with sixty triangular, equilateral congruent faces which are nearly plane, and separated by high prominent crests. They are disposed in twelve pentagonal groups, each with five faces, so that they appear as if derived from a regular pentagonal dodecahedron, the twelve regular faces of which are each divided into five congruent triangles, meeting in its centre. From the elevated corners of the polyhedron arise thirty-two radial spines (twelve in the central points of the pentagons, twenty in the meeting corners of every three pentagons). The radial spines are nearly as long as the diameter of the shell, cylindrical, spinulate, and surrounded at the distal end by a verticil of five stout, curved branches, and at the pyramidal base by a corona of twelve to sixteen basal pores. Mouth armed with a corona of twelve conical, vertical, spinulate teeth.

Dimensions.—Diameter of the shell 0.75, length of the spines 0.6.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

3. Circostephanus polygonarius, n. sp.

Shell polyhedral, with sixty to eighty subregular, triangular, concave faces, which are separated by prominent crests. From the elevated corners of the polyhedron arise thirty to forty radial spines, which are longer than the diameter of the shell, densely covered with curved bristles and three-sided prismatic, with three spirally convoluted edges. Their distal end is surrounded by a verticil of eight or nine curved branches, and their pyramidal base by a corona of eight or nine basal pores. Mouth armed with a corona of ten conical, vertical, spinulate teeth.

Dimensions.—Diameter of the shell 0.8, length of the spines 0.9.

Habitat.—South Pacific, Station 288, depth 2600 fathoms.

Subfamily 2. Haeckelinida.

Definition.—Circoporida with dimpled spherical shell, not composed of polygonal plates. The shell is covered with small roundish dimples, never polyhedral, and the radial spines are simple, not branched, and usually not regularly arranged.

Genus 716. Haeckeliana, John Murray, 1879, in schedulis, Chall. Coll.

Definition.—Circoporida with spherical shell of a peculiar dimpled, porcellanous structure, and with a variable number of simple radial main-spines which are usually not regularly arranged.

The genus Haeckeliana comprises the spherical Circoporida, with dimpled, porcellanous shell, which are widely distributed, but rather rare, in depths between 2000 and 3000 fathoms. All the known species (six in number) are very closely related, and though the extreme forms appear very different in size and structure, they are so connected by a continuous series of intermediate forms, that they may be regarded as varieties of a single species, first observed by Dr. John Murray, and called by him Haeckeliana porcellana. The number of radial spines may be from sixteen to fifty-five, and is usually between thirty and forty. Each is surrounded by a basal coronet of aspinal pores, usually five, more rarely four or six; the number, however, is not constant in any one species. Each coronet is armed with an outer ring of by-spines. The surface of the shell between the coronets is dimpled. The mouth (Pl. 114, fig. 3) is about as large as a corona, and also armed with a ring of by-spines. The structure of the thick porcellanous shell and the radial spines is different from the other Circoporida.

1. Haeckeliana porcellana, John Murray (Pl. 114, fig. 6).

Haeckeliana porcellana, John Murray, 1879, in schedulis, Chall. Coll.

Shell with forty to forty-five coronets, the majority of which have five pores (more rarely four or six). Coronets broader than their intervals, and twice as broad as the length of the by-spines. Dimples subcircular, of the same breadth as the pores. Main-spines about as long as the radius.

Dimensions.—Diameter of the shell 0.37 to 0.42, of the coronets 0.06 to 0.07.

Habitat.—South Pacific, Stations 289 to 293, depth 2025 to 2550 fathoms.

2. Haeckeliana maxima, n. sp. (Pl. 114, fig. 5).

Shell with fifty to fifty-five coronets, the majority of which have six pores (more rarely five or seven). Coronets broader than their intervals, and eight to ten times as broad as the length of the by-spines. Dimples irregularly polygonal, of about the same breadth as the pores. Radial main-spines about as long as the diameter of the shell.

Dimensions.—Diameter of the shell 0.5 to 0.52, of the coronets 0.08 to 0.09.

Habitat.—Equatorial Atlantic, Station 347, depth 2250 fathoms.

3. Haeckeliana lamarckiana, n. sp. (Pl. 114, fig. 4).

Shell with thirty-five to forty coronets, the majority of which have five pores (more rarely six or four). Coronets broader than their intervals; each funnel-shaped pore on the inside with a circle of small conical thorns. By-spines rudimentary or wanting. Dimples irregularly polygonal, half as broad as the pores. Radial main-spines shorter than the radius.

Dimensions.—Diameter of the shell 0.38 to 0.45, of the coronets 0.06 to 0.07.

Habitat.—South Atlantic, Stations 318 to 333, depth 2000 to 2900 fathoms.

4. Haeckeliana murrayana, Haeckel.

Challengeria sp., John Murray, 1876, Proc. Roy. Soc., vol. xxiv, pl. xxiv. fig. 6.

Shell with twenty to twenty-five coronets, the majority of which have five pores (more rarely four or six). Coronets of about the same breadth as their intervals, and twice as broad as the by-spines. Dimples subcircular, of about the same breadth as the pores. Radial main-spines about as long as the radius.

Dimensions.—Diameter of the shell 0.35 to 0.4, of the coronets 0.06 to 0.07.

Habitat.—Central Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms.

5. Haeckeliana goetheana, n. sp. (Pl. 114, fig. 3).

Shell with sixteen to twenty coronets, the majority of which have four pores (more rarely five and very rarely six). Coronets smaller than their intervals. By-spines very short or rudimentary. Dimples subcircular, half as broad as the pores. Radial main-spines shorter than the radius.

Dimensions.—Diameter of the shell 0.25 to 0.3, of the coronets 0.04 to 0.05.

Habitat.—North Pacific (south of Japan), Station 231, depth 2250 fathoms.

6. Haeckeliana darwiniana, n. sp. (Pl. 114, figs. 1, 2).

Shell with twenty-six to thirty-two coronets, the majority of which have five pores (rarely four or six). Coronets smaller than their intervals and than the length of the by-spines. Dimples subcircular, half as broad as the pores, Radial main-spines longer than the radius.

Dimensions.—Diameter of the shell 0.30 to 0.42, of the coronets 0.07 to 0.08.

Habitat.—North Pacific (east of Japan), Stations 241 to 245, depth 2300 to 2900 fathoms.

Family LXXXII. Tuscarorida, n. fam. (Pl. 100).

Definition.—Phæodaria with an ovate, spindle-shaped, or nearly spherical shell exhibiting a peculiar solid porcellanous structure; with a few radial pores around the base of the hollow tubules, which are symmetrically arranged around the main axis and the mouth. Surface of the shell smooth or spiny, not tabulate nor panelled. Central capsule excentric, placed in the aboral half of the shell-cavity.

The Tuscarorida, and the preceding closely allied family, the Circoporida, represent together a peculiar small group, which differs from the other Phæodaria in the singular porcellanous structure of the shell-wall, and may be called Phæocalpia; their hollow radial spines are distinguished by peculiar basal pores, forming a circle around their base. The shell of the Tuscarorida is monaxonian, ovate, spindle-shaped or nearly spherical, whilst in the Circoporida it is polyaxonian, spherical or polyhedral; the hollow radial spines are arranged in the former around the main axis, in the latter around the common central point. All Phæocalpia (the Tuscarorida as well as the Circoporida) are inhabitants of great depths, usually between 2000 and 3000 fathoms.

Though the number of Tuscarorida at present known is small (only three genera, with ten species), they represent a very distinct and remarkable family of Phæodaria, as well by their considerable size, as by the peculiar arrangement of the radial spines and the structure of the shell-wall, which in some species is more solid and thicker than in any other Radiolaria. The diameter of the shell is always more than 1 mm., usually between 1 and 2, and sometimes more than 3 mm.

The dry shell of the Tuscarorida is not hyaline and transparent as is usual in the other Radiolaria, but perfectly opaque, milk-white or yellowish-white. This opacity is caused by innumerable very fine pores, which everywhere pierce the thick, apparently solid, fundamental substance of the shell-wall. Besides those very small pores, it is also pierced by a certain number of larger pores, which are scattered at wide distances (Narr. Chall. Exp., vol. i. pl. A, fig. 15b). These larger pores or pore-channels have a diameter of about 0.01 mm., and pierce the shell-wall either in a perpendicular or in an oblique direction. Very numerous straight, simple, and thin needles, usually 0.1 to 0.2 mm. in length, similar to the thin tangential needles of the Aulacanthida, are everywhere scattered tangentially in the cement-like fundamental substance, which seems to be a peculiar carbonic silicate; their axis is parallel to the shell-surface.

The general form of the shell is somewhat different in the three genera of Tuscarorida; ovate or spherical in Tuscarora and Tuscarusa, which bear no caudal axial spine (Pl. 100, figs. 1-7), or sometimes three-sided pyramidal (fig. 4); it is spindle-shaped in Tuscaridium, which bears on the aboral pore an axial caudal spine (Pl. 100, fig. 8). In every case the main axis of the shell, determining its monaxonian fundamental form, is indicated by the mouth, which is placed in the oral pole of the main axis and prolonged into a short tube or proboscis.

The hollow apophyses, arising from the shell of the Tuscarorida, are always cylindrical, long and thin tubules, the narrow cavity of which communicates directly with the large shell-cavity. In the axis of the tubules lies a thin axial chord or funicle, composed of a few (usually three or four) siliceous threads which arise from bridges between the basal pores of the apophyses, and are twisted together like the strands of a rope. The axial funicle is connected with the thin wall of the tubular apophyses by innumerable very thin radial beams, perpendicular to the axis (Pl. 100, fig. 3a, 5b). The surface of the apophyses is almost constantly covered with numerous small bristles or spines, which are usually curved and directed towards their distal ends.

Tuscarora (Pl. 100, figs. 1-6) exhibits two different groups of apophyses, which may be distinguished according to their different position and direction as "circoral teeth" and "aboral feet"; the teeth immediately surround the opening of the mouth, whilst the feet are remote from it and usually placed in the aboral half of the body, more rarely in the equator or in the oral half. The general form and structure are the same in both groups of apophyses, but their position and direction is different; the circoral teeth are directed forwards, often parallel (at the base at least), while the aboral feet are either divergent and directed backwards, or they diverge forwards in the basal part, then form a large arch, and finally curve backwards.

The number of the aboral feet, and their position relative to the circoral teeth, are different but probably constant in each single species, and serve, in the first place, for the distinction of genera and species. Tuscarora (in restricted sense) (Pl. 100, figs. 1-6), has constantly three feet (comparable to the three cortinar feet of the tripodal Nassellaria); Tuscarusa (Pl. 100, fig. 7) has four feet, opposite in pairs and forming a regular cross; Tuscaridium, finally (Pl. 100, fig. 8), has only one foot, which is situated in the main axis, on its aboral pole, and may therefore be called a caudal spine.

The number of the circoral teeth varies from two to four, and is usually three. Originally these three teeth alternate regularly with the three aboral feet, so that the latter may be regarded as perradial, the former as interradial (Pl. 100, figs. 1-4). The proportion of the number of each group of apophyses in the different species is synoptically shown in the following table:—

Depth in Fathoms. Challenger Station. Length of the Shell. Breadth of the Shell. Number of Feet. Number of Pedal Pores. Number of Teeth. Number of Dental Pores.

1. Tuscarora bisternaria, 3000 264 2.0 1.5 3 8 3 8

2. Tusc"rora murrayi, 2000 295 2.5 1.5 3 3 3 3

3. Tusc"rora wyvillei, 2250 291 1.5 1.4 3 4 3 4

4. Tusc"rora tetrahedra, 2450 348 2.5 2.0 3 4 3 3

5. Tusc"rora tubulosa, 3000 249 1.4 1.2 3 4 2 3

6. Tusc"rora porcellana, 2650 325 1.5 1.3 3 4 2 4

7. Tusc"rora belknapii, 2025 293 2.5 1.5 3 3 4 2

8. Tuscarusa medusa, 3125 253 1.2 1.0 4 4 2 2

9. Tuscaridium cygneum, 3050 250 3.2 1.6 1 2 4 4

10. Tusca"idium lithornithium, 3000 264 3.6 1.8 1 4 4 6

a = Depth in Fathoms. b = Challenger Station. c = Length of the Shell. d = Breadth of the Shell. e = Number of Feet. f = Number of Pedal Pores. g = Number of Teeth. h = Number of Dental Pores.

(a) (b) (c) (d) (e) (f) (g) (h)

1. Tuscarora bisternaria

3000 264 2.0 1.5 3 8 3 8

2. Tuscarora murrayi

2000 295 2.5 1.5 3 3 3 3

3. Tuscarora wyvillei

2250 291 1.5 1.4 3 4 3 4

4. Tuscarora tetrahedra

2450 348 2.5 2.0 3 4 3 3

5. Tuscarora tubulosa

3000 249 1.4 1.2 3 4 2 3

6. Tuscarora porcellana

2650 325 1.5 1.3 3 4 2 4

7. Tuscarora belknapii

2025 293 2.5 1.5 3 3 4 2

8. Tuscarusa medusa

3125 253 1.2 1.0 4 4 2 2

9. Tuscaridium cygneum

3050 250 3.2 1.6 1 2 4 4

10. Tuscaridium lithornithium

3000 264 3.6 1.8 1 4 4 6

The base of the apophyses in all Tuscarorida is inflated, conical, and pierced by a small number of large ovate pores, the typical "basal pores," which occur also in the closely allied Circoporida. The number of these basal pores varies from two to eight, and is usually three or four; it never becomes in this family so great as in the Circoporida, where each circle of pores is often composed of sixteen to twenty-four or more basal pores. The number seems to be rather constant in each single species, as may be seen in the preceding Table. The pedal pores (on the base of the aboral feet) are usually larger than the dental pores (on the base of the circoral teeth). Their form is usually irregularly ovate or triangular; their outer aperture is armed with spines or bristles, which are commonly larger than in the other parts of the apophyses.

The mouth of the shell varies in form, according to the number and arrangement of the teeth on its corners. It is therefore a narrow transverse fissure, with two broad opposite lips and two corners, in the bidental forms (Pl. 100, figs. 5, 7), triangular in the tridental species (figs. 1-4), quadrangular or square in the quadridental species, Tuscarora belknapii (Narr. Chall. Exp., loc. cit., pl. A, fig. 15). The singular genus Tuscaridium (fig. 8) exhibits four teeth, which are nearly horizontally divergent in two pairs, a dorsal and a ventral pair (corresponding in position to the four feet of Tuscarusa, fig. 7); the mouth is here prolonged into a cylindrical, spinulate proboscis, which is curved towards the ventral face of the shell (fig. 8).

The central capsule of the Tuscarorida is kidney-shaped or spheroidal, scarcely half as large as the dark olive-green phæodium, which surrounds its anterior (oral) face. Usually the capsule and the phæodium together fill up the aboral half of the shell-cavity, and are separated from its walls by the calymma. The latter is pierced by numerous branched and reticulately anastomosing pseudopodia, which arise from the matrix enveloping the capsule, and pass over into a thin layer of sarcode, adjacent to the inner surface of the shell. The astropyle or the main-opening of the central capsule exhibits the usual radiate operculum and tubular proboscis of the Phæodaria (Pl. 115, fig. 3), and is directed towards the mouth of the shell. The number of the parapylæ or accessory openings seems to be variable in this family, and to correspond to the number of radial feet which arise from the shell. Therefore Tuscaridium possesses only one parapyle, which is diametrically opposite to the mouth, lies on the aboral pole of the capsule, and is directed towards the single caudal tube. Tuscarora seems to have three parapylæ, corresponding to the three radial feet, and Tuscarusa probably has four parapylæ, directed towards its four radial feet; in the latter genus, however, the capsule was not observed (the shell being empty); and in the other Tuscarorida this important and difficult anatomical question must be solved by further accurate examinations.

The nucleus is nearly half as large as the central capsule, ellipsoidal, and contains numerous nucleoli. In one specimen of Tuscarora belknapii I observed two nuclei in the central capsule, and in another specimen of the same species John Murray observed two central capsules (figured by him in the Narr. Chall. Exp., vol i. pl. A, fig. 15).

Synopsis of the Genera of Tuscarorida.

Three equidistant aboral radial feet, 717. Tuscarora.

Four equidistant aboral radial feet, 718. Tuscarusa.

One single aboral foot or terminal spine, 719. Tuscaridium.

Genus 717. Tuscarora,^[333] John Murray, 1876, in schedulis, Chall. Coll.

Definition.—Tuscarorida with three radial aboral feet, and a variable number of circoral teeth.

The genus Tuscarora comprises seven of the ten observed species of Tuscarorida, all seven agreeing in the possession of three perradial feet, which alternate originally (in four species), with three interradial teeth surrounding the mouth. The latter is armed in two other species with two teeth, and in one species with four teeth (compare above, p. 1704). The three perradial feet have a similar position as in the tripodal Nassellaria, so that they may be distinguished as an odd caudal foot and two paired lateral feet.

Subgenus 1. Tuscarantha, Haeckel.

Definition.—Shell with three perradial equidistant feet and three interradial equidistant circoral teeth, alternating regularly with the former.

1. Tuscarora bisternaria, John Murray (Pl. 100, figs. 1, 1a).

Tuscarora bisternaria, John Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pl. A, figs. 16, 16a.

Shell subspherical, with three lateral perradial feet in the equatorial zone, and three basal interradial teeth around the mouth, alternating regularly with the former. The three lateral feet arise either in the equator itself or a little above it, and are nearly horizontally expanded, descending a little towards the aboral pole. They are straight, cylindrical, twice to four times as long as the shell, geniculate at the inflated base, and covered with small thorns. A circle of six to eight basal pores in the base of each foot. The narrow mouth is triangular, surrounded by the thorny, inflated, subspherical bases of the three long, cylindrical, diverging, thorny teeth, which ascend obliquely and are longer than the shell; each tooth exhibits in the upper part of the inflated base a corona of eight to ten ovate holes.

Dimensions.—Length of the shell 2.0, breadth 1.5.

Habitat.—Central Pacific, Station 264, depth 3000 fathoms.

2. Tuscarora murrayi, n. sp. (Pl. 100, fig. 2). John Murray, 1876, L. N. 27, pl. 24, fig. 4.

Shell pear-shaped, with three circoral perradial feet in the upper third and three basal interradial teeth around the mouth. The three lateral feet are thin, cylindrical, arcuate, very bristly, arise immediately beyond the narrow tubular peristome, and ascend obliquely nearly to the height of the mouth; then they are curved downwards in a large arc, three to four times as long as the shell. The tubular peristome is about half as long as the shell, bottle-shaped, nearly three-sided prismatic, and bears three very long spinulate teeth, which in the lower half are parallel, in the upper slightly curved and diverging, at the base pear-shaped. Three ovate basal pores in the inflated base of each foot and each tooth.

Dimensions.—Length of the shell 2.5, breadth 1.5.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

3. Tuscarora wyvillei, n. sp. (Pl. 100, figs. 3, 3a-3c).

Shell subspherical, pellucid, thinner and more fragile than in the other species of the genus, with three aboral perradial feet in the lower third, and three interradial teeth around the wide mouth. The three feet are straight, conical, widely divergent, shorter than the shell, and arise from its lower third; on the inflated base of each four small ovate pores. The three teeth, alternating with them, are straight, cylindrical, arise from the margin of the mouth and diverge obliquely upwards. On the base of each foot four opposite cordate pores of very unequal size.

Dimensions.—Length of the shell 1.5, breadth 1.4.

Habitat.—South Pacific, Station 291, depth 2250 fathoms.

4. Tuscarora tetrahedra, John Murray (Pl. 100, figs. 4, 4a).

Tuscarora tetrahedra, John Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pl. A, fig. 19.

Shell tetrahedral or three-sided pyramidal, with three perradial basal feet, and three alternate, interradial, circoral teeth. The three rounded edges of the pyramid are prolonged directly over the aboral base into the three short, divergent, conical, basal feet, which are smooth and scarcely one-fourth as long as the shell. The base of each foot is pierced by four small crossed pedal pores. The narrow mouth, on the apex of the pyramid, is surrounded by three short and broad, triangular, spinulate teeth, each of which bears three slender, triangular, dental pores.

Dimensions.—Length of the shell 2.5, breadth 2.0.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

Subgenus 2. Tuscaretta, Haeckel.

Definition.—Shell with three perradial equidistant feet, and with two circoral teeth, which are opposite in the radius of the odd dorsal foot; therefore a dorsal and a ventral tooth.

5. Tuscarora tubulosa, John Murray (Pl. 100, figs. 5, 5a, 5b).

Tuscarora tubulosa, John Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pl. A, fig. 17.

Shell subspherical, with three lateral perradial feet on the upper half of the shell (above the equator), and two parallel vertical teeth on the mouth. The three feet arise between the upper and the middle third of the shell, diverge upwards, and are slightly arcuate, covered with numerous curved spines. Their base is pierced by four pedal pores. The peristome is a narrow sagittal fissure, placed in the radius of the odd or dorsal foot, and bears two opposite teeth on its two corners. The teeth are cylindrical, longer than the shell, covered with curved spines, and ascend in a parallel and vertical manner; each is perforated at the base by three large dental pores.

Dimensions.—Length of the shell 1.4, breadth 1.2.

Habitat.—North Pacific, Stations 244 to 250, depth 2050 to 3050 fathoms.

6. Tuscarora porcellana, John Murray (Pl. 100, figs. 6a, 6b).

Tuscarora porcellana, John Murray, 1819, in litteris, Narr. Chall. Exp., pl. A, fig. 18.

Shell pear-shaped, with three lateral perradial feet in the lower half of the shell, and two parallel vertical teeth on the mouth. The three lateral feet arise between the middle and the lower third of the shell, are straight, cylindrical, spinulate, about as long as the shell and diverge downwards; their base is pierced by four ovate pedal pores. The two parallel and vertical teeth are straight, shorter than half the shell, and opposite in the sagittal plane, on the two corners of the narrow mouth, in the radius of the dorsal odd foot. The base of each tooth exhibits four cordate dental pores.

Dimensions.—Length of the shell 1.5, breadth 1.3.

Habitat.—South Atlantic, Station 325, depth 2650 fathoms.

Subgenus 3. Tuscarilla, Haeckel.

Definition.—Shell with three perradial equidistant feet, and with four crossed equidistant teeth around the mouth.

7. Tuscarora belknapii, John Murray.

Tuscarora belknapii, John Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pl. A, figs. 15, 15a-15d.

Shell pear-shaped, with three lateral perradial feet in the upper third, and four crossed teeth around the mouth. The three arcuate feet are thin, cylindrical, covered with small curved thorns, and arise at the base of the peristome, between the upper and middle third of the shell; they ascend diverging to the height of the mouth, and are then curved downwards in a large arc, twice to three times as long as the shell. The base of each foot is dilated and pierced by three pedal pores. The four thin and long teeth of the peristome are similar to the feet, ascend in a slightly diverging manner, and are so placed that two opposite lie in the sagittal plane (or in the radius of the dorsal odd foot), whilst the two others are opposite in the frontal plane (perpendicular to the former). The base of each tooth exhibits two large ovate dental pores.

Dimensions.—Length of the shell 2.5, breadth 1.5.

Habitat.—South Pacific, Station 293, depth 2025 fathoms.

Genus 718. Tuscarusa,^[334] n. gen.

Definition.—Tuscarorida with four radial aboral feet and a variable number of circoral teeth.

The genus Tuscarusa differs from the preceding closely allied Tuscarora in the possession of four radial feet instead of three. The mouth of the single observed species is a narrow sagittal fissure, and armed with two opposite teeth (a dorsal and a ventral, as in the subgenus Tuscaretta). The four lateral feet form a cross, and lie opposite in pairs, in two diagonals of the square, which is bisected by the sagittal mouth.

1. Tuscarusa medusa, n. sp. (Pl. 100, figs. 7, 7a).

Shell ovate, with four crossed lateral feet in the upper third, and with two opposite teeth around the mouth. The four feet are opposite in pairs in two diameters of the shell, perpendicular one to another, and arise between the upper and middle third of the shell; they are thin, cylindrical, spinulate, arcuate, and ascend to the height of the mouth diverging upwards; then they are curved downwards in a large arc. They lie in the diagonals of the square, which is halved by the narrow and long fissure of the mouth. This lies in the original sagittal plane, and from its two corners arise the two opposite teeth (a dorsal and a ventral), diverging upwards, cylindrical and slightly curved. The base of each foot is pierced by four pedal pores, of each tooth by two dental pores.

Dimensions.—Length of the shell 1.2, breadth 1.0.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

Genus 719. Tuscaridium,^[335] n. gen.

Definition.—Tuscarorida without radial aboral feet, but with a terminal axial caudal foot, and a variable number of circoral teeth.

The genus Tuscaridium, comprising two closely allied species, differs from the two preceding genera of Tuscarorida in the absence of lateral radial feet, which are represented by a single large caudal spine placed in the main axis of the shell, at its aboral pole. The shell is therefore spindle-shaped, and not ovate or subspherical, as in the two other genera. It reaches in the two observed species a length of more than 3 mm.

1. Tuscaridium cygneum, Haeckel.

Tuscarora cygnea, John Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pl. A, fig. 20.

Shell spindle-shaped, twice as long as broad (in the transverse section circular), equally tapering towards both poles of the main axis. The aboral pole bears a thin, cylindrical, straight, caudal spine, placed in the prolongation of the main axis, and about half as long as the shell. Its base is pierced by two large opposite pedal pores. The anterior or oral pole bears a cylindrical peristome, similar to a bird's head, and curved towards the ventral face; on both sides of its neck (at right and left) a series of three or four irregular, ovate, buccal holes. The neck bears four cylindrical, spinulate, radial tubes (two on each side), crossed nearly horizontally, and placed in two diagonal planes perpendicular one to another; these planes correspond to those in which the four feet of Tuscarusa medusa lie. The base of each tube is pierced by four dental pores.

Dimensions.—Length of the shell 3.2, breadth 1.6.

Habitat.—North Pacific, Station 250, depth 3050 fathoms.

2. Tuscaridium lithornithium, n. sp. (Pl. 100, figs. 8, 8a, 8b).

Shell spindle-shaped, twice as long as broad, very similar to the preceding closely allied species. It differs from the latter in the following characters:—The curved proboscis of the peristome is broader and more spiny. The four radial tubes of the mouth and the terminal caudal spine are very spiny (in the preceding species nearly smooth). The number of buccal holes (six to eight on each side of the mouth) is twice as great as in the former. Each circoral tube is pierced at the base by six or eight (in the former by four pores), and the base of the caudal spine exhibits a cross of four pores (in Tuscaridium cygneum only two pores).

Dimensions.—Length of the shell 3.6, breadth 1.8.

Habitat.—North Pacific, Station 264, depth 3000 fathoms.

Order IV. PHÆOCONCHIA, Haeckel, 1879.

Definition.—Phæodaria with a bivalved lattice-shell, composed of two free opposite valves (a dorsal and a ventral), between which the central capsule is enclosed.

Family LXXXIII. Concharida, Haeckel, 1879 (Pls. 123-125).

Definition.—Phæodaria with a bivalved lattice-shell, which is spherical or lenticular, and composed of two equal or unequal boat-shaped valves, a dorsal and a ventral. The valves bear neither an apical latticed cupola or galea, nor hollow radial tubes. The central capsule is placed in the aboral half of the shell-cavity, and so enclosed between both valves, that its three openings lie in the open frontal fissure between them (the astropyle on the oral pole of the main axis, the two parapylæ on both sides of its aboral pole, at right and left).

The family Concharida and the two following closely allied families, the Cœlodendrida and Cœlographida, compose together the most remarkable and interesting suborder of Phæoconchia (or "Phæodaria bivalva"), differing from all the other Radiolaria in the possession of a bivalved lattice-shell, composed of two separate valves, like the shell of a Brachiopod. The central capsule is so enclosed between the two fenestrated valves that its three openings lie in the horizontal open (frontal) fissure between them, the astropyle or main-opening on the oral pole of the main axis; the two secondary openings or parapylæ on the two sides of its aboral pole, at right and left. The plane in which the three openings lie is therefore the frontal plane, dividing the entire body into a dorsal and a ventral half. The two valves, accordingly, must be considered as dorsal and ventral valves (as in the Brachiopoda), and the symmetrical halves of each valve as right and left. These halves may be always easily distinguished, since the oral pole of each valve is constantly different from the aboral pole. The voluminous phæodium always lies in the oral half, and the central capsule in the aboral half of the shell-cavity, whilst the calymma encloses the whole shell.

The Concharida differ from the other two families of bivalved Phæodaria in the absence of the apical galeas, and the branched hollow tubes arising from them. Each of these two cupolas, which are at the opposite poles of the sagittal axis (one cupola on the apex of each valve), is in the Cœlographida connected by a simple or double frenulum with a peculiar rhinocanna, or an open nasal tube directed towards the mouth; whilst the cupolas of the Cœlodendrida possess neither a rhinocanna nor a frenulum. The three families of Phæoconchia may therefore represent a phylogenetical series, the common root of which are the Concharida. From these are developed the Cœlodendrida by development of an apical cupola or galea on each valve, and of hollow radial tubes arising from it; whilst the Cœlographida are developed from the latter by production of a rhinocanna on the base of each cupola, and of one or two frenula connecting the former with the latter.

All the Concharida described in the following pages (seven genera and thirty species), are perfectly new to science, and not a single form of this interesting family was known before the explorations of the Challenger. Some species (mainly of the genera Conchidium and Conchopsis) are by no means rare, and are found in great numbers at some stations of the tropical seas (in the Pacific as well as in the Atlantic). All described species are closely allied, agree in the majority of characters, and are easy to distinguish from all the other Radiolaria. Some few forms of Concharida, however, form a direct passage to the Cœlodendrida.

Regarding the probable origin of the Concharida (and therefore also of all other Phæoconchia derived from the latter), two different hypotheses are possible. They have either been derived directly from the skeletonless Phæodina, by development of a bivalved lattice-shell; or they may be derived from Phæodaria with a simple spherical lattice-shell (Castanellida), by the halving of this latter, or its splitting into two hemispherical valves; the former hypothesis is more probable than the latter.

The two valves of the lattice-shell (Pls. 123-126) must in the Concharida (as in all other Phæoconchia) be distinguished as dorsal and ventral, and may therefore be compared with the two valves of the Brachiopoda, not with those of the Lamellibranchia. This important morphological distinction is expressed by the constant position of the central capsule within the shell-cavity. The capsule always exhibits the character of the "Tripylea" and has three tubular openings, placed in the frontal or lateral plane of the unicellular body. In the same plane lies the open frontal fissure between the two valves, and the three openings are so disposed in it that the large anterior main-opening (or the astropyle) is placed on the oral pole of the main axis, whilst the two accessory small lateral openings or parapylæ are placed on both sides of the aboral pole, at the right and left. Therefore in a dorsal or ventral view all three openings are visible (Pl. 123, figs. 1, 8a); in the usual lateral view, however, from the right or left side, only two openings are visible, the astropyle on the anterior, and one parapyle (right or left) near the posterior pole of the main axis (Pl. 123, figs. 8, 9; Pl. 124, figs. 6, 10). The posterior view (from the aboral pole) shows the two parapylæ, at right and left; in the anterior view (from the oral pole) the astropyle may be visible, but usually it is completely hidden in the dark voluminous phæodium. This latter envelops sometimes nearly the whole capsule as an opaque conglomeration of green or brown phæodella (Pl. 123, figs. 8, 9); but usually the phæodium fills up the anterior (oral) half of the shell-cavity, whilst the capsule occupies the posterior (aboral) half (Pl. 124, figs. 6, 10).

The dorsal shell-valve is in almost all Phæodaria smaller or somewhat different in shape from the ventral valve, and this difference is often very striking (Pl. 124, figs. 3-16); but in a few species both valves are so similar, that I could not discover any certain difference. This equality of the two valves occurs mainly in those Concharida which pass over into the Cœlodendrida; in these latter as well as in the Cœlographida, both valves are usually equal in size and form. Whilst the main axis (or the longitudinal axis of the body) in the two latter families of Phæoconchia seems to be normally vertical (in the living and freely floating body), in the living Concharida it is probably horizontal, so that the larger and heavier ventral valve lies below the smaller and lighter dorsal valve.

The geometrical fundamental form of the body is therefore in the Concharida dipleural or bilaterally symmetrical, and we distinguish in it the same three dimensive axes, as in all other dipleural forms. On the anterior or oral pole of the main axis (or longitudinal axis) lies the mouth of the shell, and behind it the phæodium; on the opposite posterior or aboral pole lies the hinge of the shell (comparable to the shell-hinge of the Brachiopoda) and in front of it the central capsule. The sagittal (or dorso-ventral) axis, determining the height of the shell, has on its dorsal (or upper) pole the apex or highest point of the dorsal valve, on its ventral (or lower) pole the apex or lowest point of the ventral valve. The two poles of the frontal (lateral or transverse) axis are equal and are determined by the two parapylæ of the capsule, and the corresponding points of the shell-fissure between both valves. Usually the main-axis is the longest, the frontal axis the shortest, and between both the sagittal axis.

In regard to the three dimensive planes which are determined by these three axes, perpendicular to one another, they are rarely of nearly equal size (as in some subspherical species), usually the sagittal plane (separating the right and left halves of the body) is the largest; the cinctural or equatorial plane (separating oral and aboral halves) is the smallest, and the frontal or lateral plane (separating dorsal and ventral halves) is intermediate in size. The relation of the three perimeters of these three planes corresponds to that proportion; the sagittal perimeter (in which the keel of the compressed valves lies) is the largest; the cinctural or equatorial perimeter (separating the anterior phæodium and the posterior central capsule) is the smallest, and the frontal or lateral perimeter (in which the fissure between the valves lies) is intermediate in size.