Subfamily 2. Lithopterida, Haeckel

Definition.—Quadrilonchida with two opposite transverse apophyses either on all twenty spines or only on a part of them.

Genus 338. Quadrilonche, n. gen.

Definition.—Quadrilonchida with two simple opposite apophyses either on each radial spine or only on a part of the twenty spines.

The genus Quadrilonche is the ancestral form of the Lithopterida, or of those Quadrilonchida which bear two opposite apophyses or transverse processes. In Quadrilonche these apophyses are simple, whilst they are branched in Xiphoptera and fenestrated in Lithoptera. Each of these three genera may be divided into three subgenera; in the first only the four equatorial spines are provided with apophyses, in the second twelve spines (four equatorial and eight tropical), in the third subgenus all twenty spines.

Subgenus 1. Quadriloncharium, Haeckel.

Definition.—Four large equatorial spines provided with transverse apophyses; sixteen other smaller spines simple, without apophyses.

1. Quadrilonche tetrastaura, n. sp.

Four equatorial spines very large, compressed, two-edged, each crossed in the distal third by two opposite simple apophyses. Sixteen other spines also compressed, linear, somewhat shorter than the former and only half as broad, without apophyses.

Dimensions.—Length of the four major spines 0.12, breadth 0.02; length of the sixteen minor spines 0.08, breadth 0.01.

Habitat.—Central Pacific, Station 266, surface.

2. Quadrilonche platystaura, n. sp. (Pl. , fig. 2).

Four equatorial spines lanceolate, compressed, with two opposite triangular simple apophyses in the broadest middle part. Sixteen other spines also lanceolate, much smaller, of about half the length, but only of one-fourth the breadth, without apophyses.

Dimensions.—Length of the four major spines 0.2, breadth 0.018; length of the sixteen minor spines 0.1, breadth 0.004.

Habitat.—North Pacific, Station 235, surface.

Subgenus 2. Quadrilonchidium, Haeckel.

Definition.—All twenty spines provided with transverse apophyses.

3. Quadrilonche mesostaura, n. sp. (Pl. , fig. 1).

Four equatorial spines almost of the some form and length as the sixteen others, but of double or triple the breadth; each spine in its middle third with two opposite broad triangular apophyses, in the basal third rectangular, compressed, in the distal third isosceles triangular, with simple apex.

Dimensions.—Length of the four major spines 0.16, breadth 0.01 to 0.015; length of the sixteen minor spines 0.12, breadth 0.005.

Habitat.—Tropical Atlantic, Station 345, surface.

4. Quadrilonche telostaura, n. sp.

Four equatorial spines one and a half times as long and three times as broad as the sixteen others; all twenty spines cylindrical, of equal breadth throughout their whole length, with simple conical apex; each spine crossed in the distal third by two opposite, simple, conical apophyses.

Dimensions.—Length of the four major spines 0.3, breadth 0.012; length of the sixteen minor spines 0.2, breadth 0.004.

Habitat.—South Atlantic, Station 325, surface.

Genus 339. Xiphoptera, Haeckel, 1881, Prodromus, p. 466.

Definition.—Quadrilonchida with two opposite branched (but not latticed) apophyses, either on each radial spine or only on a part of the twenty spines.

The genus Xiphoptera differs from the preceding ancestral genus Quadrilonche in the ramification of the apophyses, which bear perpendicular branches on their distal side. These are therefore parallel to the spine itself. If the branches become united by transverse beams then we get Lithoptera.

1. Xiphoptera tessaractena, n. sp.

Four equatorial spines in the outer third crossed by two opposite transverse apophyses, each of which bears on its distal side two to three branches, perpendicular to the apophysis and parallel to the spine itself. Sixteen other spines much smaller, in the outer third crossed by two simple opposite transverse apophyses.

Dimensions.—Length of the four major spines 0.18, of the sixteen minor 0.05 to 0.1.

Habitat.—North Pacific, Station 238, surface.

2. Xiphoptera dodecactena, n. sp. (Pl. , fig. 3).

Four equatorial spines one and a half times to twice as long and broad as the eight tropical spines. These twelve spines have the same form and are crossed in their distal third by two large opposite transverse apophyses, each of which bears on its distal side two to four branches, perpendicular to the apophysis and parallel to the spine. Eight polar spines much smaller than the twelve others, simple, without apophyses. The central capsule of this species exhibited a conical protuberance around the base of each individual spine.

Dimensions.—Length of the twelve larger spines 0.1 to 0.2, of the eight smaller 0.02 to 0.06.

Habitat.—Central Pacific, Station 272, surface.

3. Xiphoptera icosactena, n. sp.

Four equatorial spines about twice as long and four times as broad as the sixteen other spines. All twenty spines crossed in the outer third by two large opposite transverse apophyses, each of which bears on its distal side two to four branches perpendicular to the apophysis and parallel to the spine itself.

Dimensions.—Length of the four equatorial spines 0.26, of the sixteen smaller 0.11 to 0.14.

Habitat.—South Pacific, Station 288, surface.

Genus 340. Lithoptera, J. Müller, 1858, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 155.

Definition.—Quadrilonchida with two opposite branched and latticed apophyses, either on each radial spine or only on a part of the twenty spines.

The genus Lithoptera, founded by Johannes Müller in 1858 for the first observed Mediterranean species, Lithoptera fenestrata, differs from all other Quadrilonchida in the fenestrated form of the apophyses, which he compared to the sails of a windmill. This peculiar fenestration is effected by two to four parallel pairs of opposite apophyses, which are crossed by perpendicular branches, parallel to the spine itself. Therefore the wings or lattice-plates have quadrangular meshes and lie in one meridian plane of the spine, not in a tangential plane (as in the Acanthophracta). Commonly the lateral ends of the four broad equatorial wings are so crossed that one lateral corner of each wing lies on the upper, the other corner on the under side of both its neighbours; but sometimes the meeting corners have grown together.

Subgenus 1. Lithopteranna, Haeckel.

Definition.—Four equatorial spines with transverse apophyses; sixteen others (eight tropical and eight polar spines) simple, without apophyses.

1. Lithoptera tetraptera, n. sp. (Pl. , fig. 9).

Four equatorial spines spindle-shaped, with latticed apophyses, each crossed by two transverse beams which are connected at equal distances by four rods parallel to the spine (therefore each wing with four square meshes in a single row). Lateral corners of the neighbouring wings not meeting. Sixteen smaller spines (eight tropical and eight polar) simple, conical, without apophyses.

Dimensions.—Diagonal of the square body 0.24; length of the inner square 0.16.

Habitat.—Tropical Atlantic, Station 348, surface.

2. Lithoptera mülleri, Haeckel.

Lithoptera mülleri, Haeckel, 1862, Monogr. d. Radiol., p. 398, Taf. xx. figs. 1, 2.

Four equatorial spines four-edged, with large latticed apophyses, each crossed by three transverse beams, which are connected at irregular distances by eight to twelve rods parallel to the spine (therefore each wing with two rows of rectangular meshes). The wings are placed not perfectly in the equatorial plane, but a little obliquely, so that each wing lies with one lateral corner on the upper, with the other corner on the under side of its neighbours. Sixteen smaller spines simple, thin, cylindrical, without apophyses.

Dimensions.—Diagonal of the square body 0.3; length of the inner square 0.17.

Habitat.—Mediterranean (Messina), surface.

3. Lithoptera lamarckii, n. sp.

Four equatorial spines four-edged, with large latticed apophyses; each crossed by three transverse beams, which are connected at short distances by twelve to sixteen rods parallel to the spine (therefore each wing with two rows of hexagonal or nearly elliptical meshes). Wings placed as in Lithoptera mülleri. Sixteen smaller spines simple, thin, prismatic, without apophyses.

Dimensions.—Diagonal of the square body 0.35; length of the inner square 0.2.

Habitat.—Central Pacific, Station 271, surface.

4. Lithoptera tetragona, n. sp.

Four equatorial spines compressed, four-edged, with large latticed apophyses, each crossed by four transverse beams, which are connected at regular distances by eight to twelve rods parallel to the spine. (Therefore each wing with three rows of square meshes.) Wings placed in the equatorial plane and grown together by their meeting lateral ends, forming a square equatorial girdle of lattice-work. Sixteen smaller spines simple, thin, prismatic, without apophyses.

Dimensions.—Diameter of the square body 0.4; length of the inner square 0.22.

Habitat.—North Pacific, Station 244, surface.

Subgenus 2. Lithopterella, Haeckel.

Definition.—Twelve spines (four equatorial and eight tropical) with transverse apophyses; the eight polar spines simple, without apophyses.

5. Lithoptera quadrata, n. sp. (Pl. , fig. 10).

Twelve spines with transverse apophyses; eight (polar) spines simple, small, without apophyses. Four equatorial spines very large and stout, compressed, each crossed by four transverse beams, which are connected by eight to ten rods parallel to the spine (therefore each wing with three rows of irregular rectangular meshes). Wings placed in the equatorial plane and grown together by their meeting lateral ends, forming a square equatorial girdle of lattice-work. Eight tropical spines thin, crossed by a long and thin transverse beam, which bears on its distal side eight to ten rods parallel to the spine.

Dimensions.—Diagonal of the square body 0.35; length of the inner square 0.18.

Habitat.—South Atlantic, Station 326, surface.

6. Lithoptera dodecaptera, n. sp.

Twelve spines with transverse apophyses; eight (polar) spines simple, small, without apophyses. Four equatorial spines very large, quadrangular; each crossed by three transverse beams, which are connected by ten to twelve rods parallel to the spine (therefore each wing with two rows of square meshes). Wings placed as in Lithoptera mülleri. Eight tropical spines much thinner, crossed each by two transverse beams, which are connected by six to eight rods parallel to the spine (therefore each wing with one row of rectangular meshes).

Dimensions.—Diagonal of the square body 0.4; length of the inner square 0.25.

Habitat.—Central Pacific, Station 271, surface.

Subgenus 3. Lithopteromma, Haeckel.

Definition.—All twenty spines with transverse apophyses.

7. Lithoptera darwinii, Haeckel.

Lithoptera darwinii, Haeckel, 1879, Natürl. Schöpfungsgesch., Aufl. vii. p. 706, Taf. xvi. fig. 12.

All twenty spines with transverse apophyses; these are quite simple in the eight small cross-shaped polar spines; also simple, but bearing some perpendicular rods, in the eight thin tropical spines. Four equatorial spines very large and stout, each crossed by four transverse beams, which are connected by eight to ten rods parallel to the spine (therefore each wing with three rows of irregular rectangular meshes). Wings placed in the equatorial plane and grown partly together by their meeting lateral ends.

Dimensions.—Diagonal of the square body 0.4; length of the inner square 0.2.

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

8. Lithoptera icosaptera, n. sp.

All twenty spines with transverse apophyses, bearing one to three rows of rectangular meshes; eight polar spines small, each with a single row; eight tropical spines long and thin, each with two parallel rows. Four equatorial spines much larger and thicker, each with three parallel transverse rows of meshes. All twenty wings free, not grown together by their lateral ends.

Dimensions.—Diagonal of the square body 0.48; length of the inner square 0.24.

Habitat.—Indian Ocean, Belligemma, Ceylon (Haeckel), surface.

9. Lithoptera fenestrata, J. Müller.

Lithoptera fenestrata, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 154, Taf. xi. fig. 13.

All twenty spines with transverse apophyses, bearing one to three rows of irregular, rectangular meshes; eight polar and eight tropical spines small, each with a single row of meshes (between two parallel transverse beams). Four equatorial spines little larger, each with two rows (between three parallel transverse beams). Central capsule filled up with green pigment.

Dimensions.—Diagonal of the square body 0.3; length of the inner square 0.2.

Habitat.—Mediterranean (Saint Tropez, Nice).