Subfamily 1. Acasthostaurida, Haeckel, 1881, Prodromus, p. 466

Definition.—Quadrilonchida with simple radial spines, without apophyses.

Genus 334. Acanthostaurus, Haeckel, 1862, Monogr. d. Radiol., p. 395.

Definition.—Quadrilonchida with four equatorial spines of equal size and form, which are much larger than the sixteen other spines. Eight tropical and eight polar spines nearly equal. No apophyses.

The genus Acanthostaurus is the most simple and primitive form of the Quadrilonchida, and the common ancestral genus of this family; it is at the same time its most common and widely distributed form. Some species appear in astonishing numbers in different seas. It has been derived from Acanthometron by stronger development of the four equatorial spines, which are all of equal size and much larger than the sixteen others.

Subgenus 1. Acostaurus, Haeckel.

Definition.—All twenty spines separated, in the centre united only by the triangular faces or the meeting leaf-shaped edges of their pyramidal bases.

1. Acanthostaurus aequatorialis, n. sp.

Spines cylindrical, of nearly equal breadth throughout their whole length. Apex simple conical. Base with a large leaf-cross. Four equatorial spines of the same form as the sixteen others, but much longer and about three times as broad.

Dimensions.—Length of the four major spines 0.2 to 0.25, breadth 0.008; length of the sixteen minor spines 0.01 to 0.15, breadth 0.003.

Habitat.—Equatorial Pacific, Station 271, surface.

2. Acanthostaurus bipennis, n. sp.

Spines linear, sword-shaped, strongly compressed, two edged; of nearly equal breadth in their whole length. Apex bifid. Base with a small leaf-cross. Four equatorial spines of the same form as the sixteen others, but twice as long and as broad.

Dimensions.—Length of the four major spines 0.4 to 0.5, of the sixteen minor 0.2 to 0.3; breadth of the former 0.02, of the latter 0.01.

Habitat.—North Pacific, Station 244, surface.

3. Acanthostaurus conacanthus, n. sp.

Spines conical, short, gradually tapering from the thick base towards the simple apex. Base with large leaf-cross. Four equatorial spines more cylindrical, twice to three times as long and as broad as the sixteen others.

Dimensions.—Length of the four major spines 0.15 to 0.2, of the sixteen minor 0.05 to 0.08; basal breadth of the former 0.03, of the latter 0.012.

Habitat.—South Atlantic, Station 332, surface.

4. Acanthostaurus purpurascens, Haeckel.

Acanthostaurus purpurascens, Haeckel, 1862, Monogr. d. Radiol., p. 395, Taf. xix. figs. 1, 2.

Acanthostaurus purpurascens, R. Hertwig, 1879, Organism. d. Radiol., Taf. i. figs. 8, 9, Taf. iii. figs. 13, 15.

Acanthometra purpurascens, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 809.

Spines nearly cylindrical, with four blunt (often scarcely visible) edges, tapering slightly from the central to the distal end. Apex bifid, with two short parallel teeth. Base with a broad leaf-cross. Four equatorial spines one and a half times to twice as long and broad as the sixteen others. Central capsule cruciate, with four arms (enveloping the basal part of the four large spines); filled up with yellow bodies and purple granules. Calymma large, with a network of purple granules. The four main spines are constantly much larger than the sixteen others, but in variable proportion. The eight polar spines are sometimes rudimentary.

Dimensions.—Length of the four major spines 0.3 to 0.4, of the sixteen minor 0.15 to 0.3; breadth of the former 0.012, of the later 0.008 or less.

Habitat.—Mediterranean (Messina); Atlantic, Stations 348 to 354, surface.

5. Acanthostaurus pallidus, Haeckel.

Acanthostaurus pallidus, Haeckel, 1862, Monogr. d. Radiol., p. 396.

Acanthometra pallida, Claparède et Lachmann, 1858, Études sur les Infusoires, &c., p. 461, Taf. xxiv. fig. 6.

Spines four-sided prismatic, with four blunt edges, of nearly equal breadth throughout their whole length. Apex bifid. Base with a small leaf-cross. Four equatorial spines much larger than the sixteen others. Central capsule spherical, transparent, containing some yellow bodies.

Dimensions.—Length of the four main spines 0.12 to 0.2, of the sixteen others 0.04 to 0.08; breadth of the former 0.01, of the latter 0.004.

Habitat.—North Atlantic, west coast of Norway, Claparède; Færöe Channel, John Murray.

6. Acanthostaurus forceps, Haeckel.

Acanthostaurus forceps, Haeckel, 1862, Monogr. d. Radiol., p. 396, Taf. xix. figs. 3, 4.

Acanthometra forceps, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 809.

Spines pincer-shaped, linear, compressed, cleft nearly throughout their whole length into two parallel thin, straight branches, which are united only at the pyramidal base and by means of a small bridge in the middle part. Four main spines twice as long and as broad as the sixteen others. Central capsule square, filled up with red pigment, and containing yellow bodies. The diagonals of the square are the two equatorial axes.

Dimensions.—Length of the four main spines 0.1, of the sixteen others 0.05; breadth of the former 0.01, of the latter 0.005.

Habitat.—Mediterranean (Messina); North Atlantic, Canary Islands, Station 354, surface.

7. Acanthostaurus hastatus, Haeckel.

Acanthostaurus hastatus, Haeckel, 1862, Monogr. d. Radiol., p. 397, Taf. xix. fig. 5.

Acanthometra hastata, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 809.

Spines of very different size and form; four equatorial spines cylindrical in the basal half, spear-shaped or lanceolate in the distal half, with thin edges, little longer, but five to eight times as broad as the sixteen smaller spines, which are cylindrical, of equal breadth throughout their whole length, with bifid apex. Base of all twenty spines pyramidal, without leaf-cross. Central capsule yellow, spherical, or lenticular.

Dimensions.—Length of the four major spines 0.066, breadth in the middle 0.005, on the apex 0.008; length of the sixteen smaller spines 0.054, breadth 0.001.

Habitat.—Mediterranean (Messina), surface.

Subgenus 2. Staurolithium, Haeckel, 1862, Monogr. d. Radiol., p. 401.

Definition.—All twenty spines in the centre melted and grown together, forming one single, star-like piece of acanthin.

8. Acanthostaurus cruciatus, Haeckel.

Staurolithium cruciatum, Haeckel, 1862, Monogr. d. Radiol., p. 401, Taf. xx. fig. 6.

Astrolithium cruciatum, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 811.

Spines cylindrical, of equal breadth throughout their whole length. Apex simple conical. Four equatorial spines twice as long and broad as the sixteen other spines. All twenty spines in the centre melted and grown together, forming a single piece of acanthin. Central capsule spherical, red-brown, opaque.

Dimensions.—Length of the four equatorial spines 0.12, breadth 0.006; length of the sixteen smaller spines 0.06, breadth 0.003.

Habitat.—Mediterranean (Messina), surface.

Genus 335. Belonostaurus, n. gen.

Definition.—Quadrilonchida with four equatorial spines of equal size and form, which are much larger than the sixteen other spines. Eight tropical and eight polar spines very different. No apophyses.

The genus Belonostaurus differs from the preceding Acanthostaurus in the unequal size and form of the eight tropical and the eight polar spines; the latter are much smaller than the former and often quite rudimentary, so that the skeleton appears composed only of twelve spines, four larger equatorial and eight smaller tropical spines. The central bases of the polar spines are constantly preserved. The central capsule is a flattened square disk.

1. Belonostaurus quadratus, n. sp.

Four equatorial spines little compressed, almost cylindrical in the basal half, lanceolate, broader, with simple apex in the distal half. Eight tropical spines a little shorter, but only half as broad, sword-shaped, two-edged, of equal breadth, with simple apex. Eight polar spines very short, conical, also with simple apex. Base without leaf-cross, a simple pyramid.

Dimensions.—Length of the four equatorial spines 0.18, of the eight tropical spines 0.14, of the eight polar spines 0.04.

Habitat.—Central Pacific, Station 271, surface.

2. Belonostaurus bicuspis, n. sp.

Four equatorial spines compressed, almost lanceolate in the basal half, bifid, with two large, bent, little divergent horns in the distal half. Eight tropical spines nearly of the same form, but only half as large, with much smaller horns. Eight polar spines rudimentary, very short, conical, with simple apex. Base with a large leaf-cross.

Dimensions.—Length of the four equatorial spines 0.2, of the eight tropical spines 0.1, of the eight polar spines 0.02.

Habitat.—Central Pacific, Station 263, surface.

Genus 336. Lonchostaurus, Haeckel, 1862, Monogr. d. Radiol., p. 397 (sensu emendato).

Definition.—Quadrilonchida with four equatorial spines of unequal size and form; the principal spines (in the longitudinal axis) larger than the lateral spines (in the transverse axis); both opposite spines of each pair equal. Sixteen other spines much smaller (often the eight tropical larger than the eight rudimentary polar spines). No apophyses.

The genus Lonchostaurus differs from the two preceding genera in the unequal size and shape of both equatorial pairs of spines, whilst the two opposite spines of each pair are equal. Therefore the equatorial plane is here a rhombus, not a square, as in the preceding genera. We encounter here for the first time the differentiation of the two equatorial axes, the longitudinal (or hydrotomical) and the transverse (or geotomical) axis. The sixteen other spines are constantly smaller (often also the eight polar more or less rudimentary).

1. Lonchostaurus rhomboides, n. sp. (Pl. , fig. 6).

Four equatorial spines cylindrical, twice to three times as broad as the sixteen smaller spines, conical at the distal apex; the two opposite spines of the longitudinal axis twice as long as those of the transverse axis. Sixteen smaller spines conical at the base, with simple bristle-shaped apex. The surface of the rhombical calymma, including the spines, was covered in the figured specimen with small plates like those of Sphærocapsa.

Dimensions.—Length of the cross (longitudinal axis) 0.24, breadth (transverse axis) 0.12.

Habitat.—South Pacific, Station 302, depth 1450 fathoms.

2. Lonchostaurus lanceolatus, n. sp.

Four equatorial spines compressed, lanceolate, tapering equally from the middle towards the two ends; the two opposite spines of the longitudinal axis one and a half times as long as those of the transverse axis. Sixteen smaller spines compressed, linear, two-edged, half as long and only one-fourth as broad as the two longitudinal spines.

Dimensions.—Length of the equatorial cross 0.3, breadth 0.2.

Habitat.—Central Pacific, Station 272, surface.

3. Lonchostaurus bifidus, n. sp.

Four equatorial spines compressed, nearly rectangular, forked, with two long and thin, bent, little divergent horns; the two opposite spines of the longitudinal axis about one-third longer and broader than those of the transverse axis. Sixteen smaller spines of the same form, also forked, but the eight tropical only half as large, and the eight polar spines scarcely one-fourth as large as the two longitudinal spines.

Dimensions.—Length of the equatorial cross 0.36, breadth 0.26.

Habitat.—South-west Pacific, Station 166, surface.

4. Lonchostaurus bifurcus, n. sp. (Pl. , fig. 4).

Four equatorial spines nearly rhomboidal, about one and a half times as large as the eight tropical and three times as large as the eight polar spines; the two opposite spines of the longitudinal axis only with two large divergent straight horns; the two spines of the transverse axis somewhat shorter, with four short horns (the two outer horns longer than the two inner). Eight tropical spines doubly forked, each with four thin bristle-shaped horns. Eight polar spines very short, each with two thin bristle-shaped, much divergent horns.

Dimensions.—Length of the equatorial cross 0.34, breadth 0.28.

Habitat.—North-west Pacific, Station 236, surface.

5. Lonchostaurus rhombicus, n. sp.

Four equatorial spines nearly rhomboidal, tapering from the broader middle towards the two ends. Leaf-cross of their base very large. The two opposite spines of the longitudinal axis about one-third larger than the two spines of the transverse axis. Eight tropical spines of the same form, but only half as large. Eight polar spines rudimentary, very short, conical.

Dimensions.—Length of the equatorial cross 0.4, breadth 0.3.

Habitat.—North Pacific, Station 253, surface.

6. Lonchostaurus crystallinus, n. sp. (Pl. , fig. 5).

Four equatorial spines lanceolate or rhomboidal, with broad leaf-cross at the base, of a peculiar crystalline structure and a lamellated surface, both opposite spines of the longitudinal axis twice as large as the two spines of the transverse axis. Eight tropical spines of similar form, but only half as large, and with a very large, extremely prominent, lamellated leaf-cross. Eight polar spines quite rudimentary, scarcely prominent.

Dimensions.—Length 0.36, breadth 0.2.

Habitat.—Central Pacific, Station 271, surface.

Genus 337. Zygostaurus, n. gen.

Definition.—Quadrilonchida with four equatorial spines of unequal size and form; both lateral spines (in the transverse axis) equal; but both principal spines (in the longitudinal axis) very different, the frontal larger than the caudal. Sixteen other spines much smaller (often the eight tropical larger than the eight rudimentary polar spines). No apophyses.

The genus Zygostaurus differs from all other Staurolonchida in the peculiar differentiation of the four equatorial spines; the two opposite spines of the hydrotomical or longitudinal axis being very different in size and form (the frontal spine forked, the caudal spine simple); whilst the two opposite spines of the geotomical or lateral axis (perpendicular to the former) are equal, forked, but different in shape from the former. Therefore the geometrical fundamental form of the body in this remarkable genus becomes "amphithect" or "bilateral" in the widest signification of this term (comp. my General Morphology, vol. i. pp. 480, 482). Of the three different dimensive axes one (the longitudinal) exhibits unequal poles, whilst the two other (the sagittal and lateral) axes exhibit equal poles.

1. Zygostaurus amphithectus, n. sp. (Pl. , fig. 7).

Frontal spine (c1) little different from the two lateral spines; each with two divergent curved horns, which are equal and of about the same length as the simple broad basal part. Caudal spine (c3) simple, spindle-shaped, about as long as the frontal spine. Tropical spines little smaller than the three former, and of the same symmetrical forked form. Eight polar spines much smaller, but also forked, with thin bristle-shaped branches.

Dimensions.—Length of the cross (longitudinal axis) 0.5, breadth (lateral axis) 0.4.

Habitat.—Central Pacific, Station 272, surface.

2. Zygostaurus longicornis, n. sp.

Frontal spine (c1) little different from the two lateral spines, each with two divergent curved horns, which are equal and of about the same length as the simple broad basal part. Caudal spine (c3) simple, lanceolate, shorter than the frontal spine. Eight tropical spines in the basal part smaller than the three former, but with much longer fork-branches, which are prolonged into very thin and long bristles. Eight polar spines rudimentary, very short.

Dimensions.—Length of the equatorial cross 0.4, breadth 0.3.

Habitat.—South Pacific, Station 295, surface.

3. Zygostaurus cornutus, n. sp.

Frontal spine (c1) little different from the two lateral spines, each with two divergent straight horns, which are shorter than the basal part. Caudal spine (c3) simple, triangular, shorter than the three former. Eight tropical spines of equal size and form, doubly forked, each with four thin, bristle-shaped, little divergent teeth. Eight polar spines short, simply forked.

Dimensions.—Length of the equatorial cross 0.5, breadth 0.4.

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

4. Zygostaurus caudatus, n. sp.

Frontal spine (c1) very different from the others, pincer-shaped, with two long, nearly parallel slightly bent horns. Lateral spines (c2 and c4) only half as long, with two short, nearly parallel horns. Caudal spine (c3) very long and stout, spindle-shaped, about twice as long as the frontal spine. Eight tropical spines of equal size and form, symmetrical, with two long and thin, divergent horns. Eight polar spines short and stout, with two divergent horns.

Dimensions.—Length of the equatorial cross 0.8, breadth 0.3.

Habitat.—Central Pacific, Station 265, surface.

5. Zygostaurus frontalis, n. sp.

Frontal spine (c1) very different from the others, with two very long, divergent, stout branches. Lateral spines (c2 and c4) only half as long, each with two stout, nearly parallel horns of equal length. Caudal spine (c3) simple, sword-like, shorter than the three former. Eight tropical spines of equal size and form, symmetrical, of the same shape as the two lateral, but only half as large. Eight polar spines very small, rudimentary, each with two short teeth.

Dimensions.—Length of the equatorial cross 0.7, breadth 0.5.

Habitat.—Central Pacific, Station 274, surface.

6. Zygostaurus sagittalis, n. sp. (Pl. , fig. 8).

Frontal spine (c1) very different from the others, with two equal, strongly divergent, bent horns. Lateral spines (c2 and c4) little smaller, but with two very unequal horns (the anterior shorter than the posterior). Caudal spine (c3) simple, sword-like or triangular, two-edged, longer than the frontal spine. Eight tropical spines different, the four anterior (b1, b4, d1, d4) smaller, with longer horns; the four posterior (b2, b3, d2, d3) broader, with shorter horns; the anterior horn of each tropical spine is longer than the posterior. Eight polar spines rudimentary, simple, very short.

Dimensions.—Length of the equatorial spine-cross 0.6, breadth 0.4.

Habitat.—Central Pacific, Station 271, surface.