Family XIV. Artiscida, Haeckel (Pl. , figs. 9, 10; Pl. , fig. 5)

Artiscida, Haeckel, 1881, Prodromus, p. 462.

Definition.—Prunoidea with an ellipsoidal twin-shell divided by an equatorial stricture into two communicating hemiellipsoidal or hemispherical chambers, without enclosed medullary shell. Central capsule ellipsoidal, with or without equatorial stricture.

The family Artiscida has a simple fenestrated outer shell, like that of the Ellipsida, but differs from these in the presence of an equatorial constriction, by which it assumes a characteristic twin form, somewhat similar to a violin (Pl. , figs. 9, 10). From the Cyphinida, which have the same form of the cortical shell, the Artiscida differ in the absence of the medullary shell. It is possible that the Artiscida are descended from the Cyphinida (by loss of the medullary shell), but it is more probable that they arise from the Ellipsida by an annular constriction in the equatorial plane (perhaps the formation of the shell originally took place while the central capsule was undergoing division). Both halves of the twin shell are always of the same size and form. Its outer surface is either smooth or covered with radial spines (Artiscus, Pl. , fig. 9). Sometimes on the opposite poles of the main axis are developed solid spines (Stylartus, Pl. , fig. 5) or hollow fenestrated tubes (Cannartus, Pl. , fig. 10).

The Central Capsule is either simply ellipsoidal, or has also an equatorial constriction, which divides it into two equal halves. It is constantly smaller than the surrounding shell, and separated from its inner surface by a thicker or thinner jelly-mantle, the calymma.

Synopsis of the Genera of Artiscida.

On the poles of the main axis neither solid spines nor hollow tubes, 152. Artiscus.

On the poles of the main axis two solid spines (or bunches of spines), 153. Stylartus.

On the poles of the main axis two hollow fenestrated tubes, 154. Cannartus.

On the poles of the main axis neither solid spines nor hollow tubes,

152. Artiscus.

On the poles of the main axis two solid spines (or bunches of spines),

153. Stylartus.

On the poles of the main axis two hollow fenestrated tubes,

154. Cannartus.

Genus 152. Artiscus, Haeckel, 1881, Prodromus, p. 462.

Definition.—Artiscida without peculiar polar appendages (without strong solid spines or hollow fenestrated tubes on the poles of the main axis).

The genus Artiscus represents the most simple and primitive form of the Artiscida, and may therefore be regarded as the ancestral form of this subfamily. It resembles an ordinary double loaf, composed of two equal, nearly ellipsoidal fenestrated shells separated by the stricture in the equatorial plane. Artiscus can be derived from Cenellipsis simply by this equatorial constriction. But it can also be derived from Cyphanta by loss of the medullary shell.

Subgenus 1. Artiscium, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial rods or spines.

1. Artiscus paniscus, n. sp.

Pores of the shell regular, hexagonal, four times as broad as the bars; ten to twelve pores on the half meridian, eight to nine on the half equator. Surface smooth. (The network of this species is quite the same as that of the proximal cameræ of Panartus diploconus, Pl. , fig. 1.)

Dimensions.—Main axis of the shell 0.12, equatorial axis 0.07; meshes 0.013, bars 0.003.

Habitat.—Pacific, central area, Station 271, depth 2425.

2. Artiscus facetus, n. sp.

Pores of the shell regular, circular, with prominent hexagonal frame, twice as broad as the bars; twenty-two to twenty-four pores on the half meridian, fourteen to fifteen on the half equator. Surface a little thorny. (The shell of this species exhibits nearly the same formation as that of Cyphonium virgineum, Pl. , fig. 12, but without enclosed medullary shells.)

Dimensions.—Main axis of the shell 0.15, equatorial axis 0.09; meshes 0.01, bars 0.005.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

3. Artiscus paniculus, n. sp.

Pores of the shell regular, circular, without hexagonal frame, as broad as the bars; fourteen to sixteen pores on the half meridian, ten to eleven on the half equator. Surface quite smooth.

Dimensions.—Main axis of the shell 0.13, equatorial axis 0.06; meshes 0.01, bars 0.01.

Habitat.—Fossil in the Tertiary rocks of Barbados (Haeckel).

4. Artiscus panarius, n. sp.

Pores of the shell irregular, roundish, twice to four times as broad as the bars; sixteen to eighteen pores on the half meridian, twelve to thirteen on the half equator. Surface smooth.

Dimensions.—Main axis of the shell 0.11, equatorial axis 0.06; meshes 0.005 to 0.02, bars 0.001 to 0.004.

Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.

Subgenus 2. Artidium, Haeckel, 1881, Prodromus, p. 462.

Definition.—Surface of the shell covered with radial rods or spines.

5. Artiscus elegans, n. sp.

Pores of the shell regular, circular, with hexagonal frames, twice as broad as the bars; fourteen pores on the half meridian, eight to nine on the half equator. From every corner of the hexagonal frames (between every three pores) starts a thin, three-sided pyramidal spine, twice as large as a pore.

Dimensions.—Main axis 0.13, equatorial axis 0.08; meshes 0.007, bars 0.004; spines 0.015 long.

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

6. Artiscus nodosus, n. sp. (Pl. , fig. 9).

Pores of the shell subregular, circular, without hexagonal frame, three times as broad as the bars; sixteen to eighteen on the half meridian, ten to twelve on the half equator. Irregularly scattered on the whole surface a variable number (twenty-five to thirty in all) of stout short radial spines or rather blunt rods; the length and thickness of these is the same, and equals the size of two to three meshes; its form resembles a truncated six-sided pyramid.

Dimensions.—Main axis 0.11, equatorial axis 0.08; meshes 0.01, bars 0.003; length and thickness of the radial sticks 0.02.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

7. Artiscus hystrix, n. sp.

Pores of the shell irregular, roundish, of very unequal size and dissimilar form, twice to eight times as broad as the bars; ten to fifteen on the half meridian, seven to nine on the half equator. Irregularly scattered on the whole surface a large number of thin conical spines, about as large as the meshes, partly directed radially, partly obliquely. (The shell of this species resembles very much that of Cyphonium ceratospyris (p. ) = Didymocyrtis ceratospyris, Monogr. d. Radiol., 1862, Taf. xxii. fig. 14, but is without the enclosed inner shells.)

Dimensions.—Main axis 0.12, equatorial axis 0.07; meshes 0.004 to 0.02, bars 0.002 to 0.005; spines 0.01 to 0.02.

Habitat.—Atlantic, Eastern Tropical part, Station 346, surface.

Genus 153. Stylartus, Haeckel, 1881, Prodromus, p. 462.

Definition.—Artiscida with two strong, solid, polar spines, or two bunches of polar spines, opposite on the two poles of the main axis.

The genus Stylartus differs from Artiscus by the production of two large opposite spines in the main axis, starting from both poles of it; sometimes every spine is surrounded by a group of smaller radial spines. The genus is nearly allied to Ellipsoxiphus (p. ), and differs from it only in the equatorial stricture of the ellipsoidal shell. But it may also be derived from the similar Cyphinus (Pl. , fig. 14) by loss of the medullary shell.

Subgenus 1. Stylartella, Haeckel.

Definition.—On each pole of the main axis only one single large spine.

1. Stylartus bipolaris, n. sp. (Pl. , fig. 5).

Shell thick walled, rough; both its chambers nearly spherical, with irregular, roundish pores, twice to four times as broad as the bars; eight to ten on the half equator of each chamber. Polar spines very strong, conical, as long as the greatest breadth.

Dimensions.—Length of the shell (without spines) 0.18, greatest breadth 0.13; length of the polar spines 0.13, basal breadth 0.03.

Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.

2. Stylartus bicuspis, n. sp.

Shell thin walled, smooth, with regular, circular pores, twice as broad as the bars; twelve to fourteen on the half equator of each chamber. Polar spines very stout, straight, three-sided pyramidal, half as long as the shell.

Dimensions.—Length of the shell 0.16, greatest breadth 0.12; length of the polar spines 0.08, basal thickness 0.025.

Habitat.—Pacific, central area. Station 266, depth 2750 fathoms.

Subgenus 2. Stylartura, Haeckel.

Definition.—On each pole of the main axis a bunch of several spines.

3. Stylartus palatus, n. sp.

Shell thick walled, thorny, with irregular, roundish pores, twice to three times as broad as the bars; fifteen to eighteen on the half equator of each chamber. On each pole of the main axis a large conical spine, surrounded by a group of ten to fifteen smaller spines, one-third to two-thirds as long as the breadth of the deep equatorial stricture.

Dimensions.—Length of the shell 0.14, greatest breadth 0.09; length of the polar spines 0.03 to 0.06, basal breadth 0.005 to 0.015.

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

4. Stylartus penicillus, n. sp.

Shell thin walled, smooth, with irregular, roundish pores, three to four times as broad as the bars; ten to twelve on the half equator of each chamber. On each pole of the main axis a brush-like bunch of twenty to thirty thin conical radial spines, half as long as the shell.

Dimensions.—Length of the shell 0.15, greatest breadth 0.1; length of the polar spines 0.08, basal breadth 0.005.

Habitat.—Equatorial Atlantic, Station 347, surface.

Genus 154. Cannartus, Haeckel, 1881, Prodromus, p. 462.

Definition.—Artiscida with two hollow polar tubes (fenestrated cylindrical or conical tubuli, opposite on the two poles of the main axis).

The genus Cannartus differs from Artiscus by the production of two opposite hollow tubes on both poles of the main axis. The cavity of the conical or cylindrical fenestrated tubes communicates freely with that of the shell; the network in both is the same. The distal end of the tubes is nearly always broken off, sometimes closed, with a conical apex. Cannartus can be derived either from Pipettella by a transverse equatorial constriction, or from Cannartiscus by the loss of the medullary shell, or from Artiscus by the production of the polar tubes.

1. Cannartus violina, n. sp. (Pl. , fig. 10).

Pores of the shell subregular, circular, twice to three times as broad as the bars; eighteen to twenty on the half meridian, fourteen to sixteen on the half equator. Shell-wall in the "tropical zone" of both halves thickened. Polar tubes nearly cylindrical, about as long as the main axis, distal ends broken off.

Dimensions.—Main axis 0.14, equatorial axis 0.09; meshes 0.008, bars 0.003; length of the polar tubes 0.12, breadth 0.02 to 0.03.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

2. Cannartus bitubulus, n. sp.

Pores of the shell regular, circular, hexagonally framed, of the same breadth as the bars; fourteen to sixteen on the half meridian, ten to twelve on the half equator. Polar tubes cylindrical, longer than the main axis, sulcated, distal ends broken off. (Similar to Pipetta tuba, Pl. , fig. 7, but with equatorial stricture and without medullary shell.)

Dimensions.—Main axis 0.16, equatorial axis 0.12; meshes and bars 0.006; length of the polar tubes 0.2, breadth 0.025.

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

3. Cannartus biscottus, n. sp.

Pores of the shell irregular, roundish, twice to three times as broad as the bars; ten to twelve on the half meridian, six to eight on the half equator. Polar tubes conical, shorter than the main axis, with closed apex. (Similar to Cannartidium bicinctum, Pl. , fig. 18, but without enclosed medullary shell.)

Dimensions.—Main axis 0.11, equatorial axis 0.07; meshes 0.005 to 0.01, bars 0.003; length of the polar tubes 0.08, breadth on the base 0.03.

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