Subfamily 2. Larcospirida, Haeckel

Definition.—Lithelida with double, trizonal, or Larnacilla-shaped medullary shell.

Genus 306. Larcospira, n. gen.

Definition.—Lithelida with double, trizonal, or Larnacilla-shaped medullary shell; cortical shell subspherical or lentelliptical, constructed of a simple or double spiral of the transverse girdle (or primary cortical girdle); the spiral lamella revolving around the principal axis.

The genus Larcospira begins the interesting series of the Larcospirida, or of those Lithelida in which the medullary shell is formed by a trizonal or Larnacilla-shaped lattice-shell, and the cortical shell by spiral turnings of one of the three girdles, which compose the cortical shell of the Pylonida. In Larcospira, as the oldest and most simple form of Larcospirida, the spiral is formed by the transverse girdle, or the first girdle of the Diplozonaria, the only cortical girdle of Amphipyle. If in this genus one of both wings of the transverse girdle grow stronger than the other and overgrow the latter, turning around the principal axis, we reach the characteristic form of Larcospirema, the first subgenus of Larcospira; but if afterwards the second wing follow the example of the first, and overgrow it from the other side, we reach the typical form of the second subgenus, Larcospironium. In this latter subgenus the spiral becomes double, whilst in the former it remains simple.

Subgenus 1. Larcospirema, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell simple; only one single wing of the transverse girdle turning around the principal axis.

1. Larcospira lentelliptica, n. sp.

Cortical shell with smooth surface, four times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a half times as long as broad, without constrictions. One lateral wing of the transverse girdle is more strongly developed and turns around the other in two to three simple spiral turns.

Dimensions.—Length of the cortical shell 0.2, breadth 0.16; length of the medullary shell 0.05, breadth 0.04.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

2. Larcospira quadrangula, n. sp. (Pl. , fig. 3).

Cortical shell with thorny surface, three times as long as the lentelliptical medullary shell. Perimeter of the lateral plane nearly quadrangular, with four rounded corners (on the poles of two crossed diagonal axes), one and a third times as long as broad, with one sagittal constriction at the poles of the principal axis. One lateral wing of the transverse girdle turns around the other in one and a half to two simple spiral turns.

Dimensions.—Length of the cortical shell 0.18, breadth 0.14; length of the medullary shell 0.06, breadth 0.04.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

3. Larcospira sexangula, n. sp.

Cortical shell with spiny surface, four times as long as the hexagonal medullary shell. Perimeter of the lateral plane nearly hexagonal, one and a half times as long as broad, with six rounded corners (two on the poles of the principal axis, four on the poles of two crossed diagonal axes), with three slight ring-like constrictions. One lateral wing of the transverse girdle turns around the other in two to two and a half simple spiral turns.

Dimensions.—Length of the cortical shell 0.24, breadth 0.16; length of the medullary shell 0.06, breadth 0.04.

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

Subgenus 2. Larcospironium, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell double; both wings of the transverse girdle turning around the principal axis.

4. Larcospira oliva, n. sp.

Cortical shell with smooth surface, six times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a fourth times as long as broad, without constrictions. Both lateral wings of the transverse girdle turn round one another and form one and a half to two double spiral turns.

Dimensions.—Length of the cortical shell 0.25, breadth 0.2; length of the medullary shell 0.04, breadth 0.035.

Habitat.—Antarctic Ocean, Station 157, depth 1950 fathoms.

Genus 307. Pylospira, n. gen.

Definition.—Lithelida with double, trizonal or Larnacilla-shaped medullary shell; cortical shell subspherical or lentelliptical, constructed of a single or double spiral of the lateral girdle (or second cortical girdle); the spiral lamella revolving round the sagittal axis.

The genus Pylospira follows after Larcospira as the second genus of Larcospirida; but in this latter the spiral of the cortical shell is formed by the transverse girdle (or the first lattice-girdle of the Diplozonaria), whilst in Pylospira it is produced by the lateral girdle, or the second lattice-girdle of that group. Therefore Pylospira may be derived phylogenetically from Tetrapyle in the same manner as Larcospira from Amphipyle. Whilst in this latter the first cause of the spiral turning, the unequal growth of both girdle-wings, proceeds from the transverse girdle, in Pylospira it proceeds from the lateral girdle. One of its wings overgrows the other, turning around the sagittal axis. If the second wing do not become developed, the spiral remains simple and represents the subgenus Pylospirema; but if afterwards the second wing follow the example of the first and overgrow it from the other side, we reach the typical form of the second subgenus, Pylospironium, with a double spiral.

Subgenus 1. Pylospirema, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell simple, only one single wing of the lateral girdle turning around the sagittal axis.

1. Pylospira tetrapyle, n. sp.

Cortical shell with thorny surface, five times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a half times as long as broad. Four internal gates (as in Tetrapyle, between the complete lateral wings of the transverse girdle) kidney-shaped. One principal wing of the lateral girdle turns around the other in one and a half to two simple spiral turns.

Dimensions.—Length of the cortical shell 0.21, breadth 0.15; length of the medullary shell 0.04, breadth 0.03.

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

2. Pylospira octopyle, n. sp. (Pl. , fig. 4).

Cortical shell with thorny surface, three times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical or nearly hexagonal, with four rounded corners (on the poles of two crossed diagonal axes), one and a third times as long as broad. Eight internal egg-shaped gates (as in Octopyle), between the complete lateral wings of the transverse girdle, and two axial beams in the principal axis. One single wing of the lateral girdle turns around the other in two to three simple spiral turns.

Dimensions.—Length of the cortical shell 0.18, breadth 0.14; length of the medullary shell 0.06, breadth 0.035.

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

Subgenus 2. Pylospironium, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell double; both wings of the lateral girdle turning around the sagittal axis.

3. Pylospira cymbium, n. sp.

Cortical shell with smooth surface, seven times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a third times as long as broad. Four internal kidney-shaped gates between the complete lateral wings of the transverse girdle (as in Tetrapyle). Both principal wings of the lateral girdle turn round one another in two to two and a half double spiral turns.

Dimensions.—Length of the cortical shell 0.22, breadth 0.17; length of the medullary shell 0.03, breadth 0.025.

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

Genus 308. Tholospira, n. gen.

Definition.—Lithelida with double, trizonal or Larnacilla-shaped medullary shell; cortical shell subspherical or lentelliptical constructed of a simple or double spiral of the sagittal girdle (or third cortical girdle); the spiral lamella revolving around the transverse axis.

The genus Tholospira represents the third genus of Larcospirida. Whilst the spiral growth of the cortical shell is produced in Larcospira by the first (transverse) girdle of the Diplozonaria, in Pylospira by the second (lateral) girdle, in Tholospira it is effected by the third or sagittal girdle, which we found complete in Pylonium. If in this genus one wing of the sagittal girdle overgrow the other remaining one and turn around the transverse axis, we get Tholospirema, the first subgenus of our genus, with simple spiral; but if afterwards the second wing follow the example of the first, and overgrow it from the other side, we get Tholospironium, with double spiral.

Subgenus 1. Tholospirema, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell simple, only one single wing of the sagittal girdle turning around the transverse axis.

1. Tholospira nautiloides, n. sp.

Cortical shell with smooth surface, five times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a half times as long as broad. Four internal kidney-shaped gates (between the lateral wings of the transverse girdle, as in Tetrapyle). One wing of the sagittal girdle turns around the other in two to two and a half simple spiral turns.

Dimensions.—Length of the cortical shell 0.24, breadth 0.18; length of the medullary shell 0.05, breadth 0.04.

Habitat.—Indian Ocean, between Ceylon and Socotra, Haeckel, surface.

2. Tholospira spinosa, n. sp.

Cortical shell covered with numerous (sixty to eighty or more) simple, bristle-like radial spines, about the length of the shell. Perimeter of the lateral plane nearly quadrangular, with four rounded corners (on the poles of two crossed diagonal axes), one and a half times as long as broad. Eight internal egg-shaped gates (between the lateral wings of the transverse girdle and two axial beams in the principal axes, as in Octopyle). One wing of the sagittal girdle turns around the other in two to three simple spiral turns.

Dimensions.—Length of the cortical shell 0.27, breadth 0.18; length of the medullary shell 0.04, breadth 0.03.

Habitat.—South Pacific, Station 288, surface.

3. Tholospira dendrophora, n. sp. (Pl. , fig. 6).

Cortical shell covered with numerous (forty to fifty or more) branched radial spines, about half as long as the shell; each spine with two to six dichotomous branches. Perimeter of the lateral plane elliptical, one and a third times as long as broad. Eight internal egg-shaped gates, as in the foregoing species. One single wing of the sagittal girdle turns around the other in three to four spiral turns.

Dimensions.—Length of the cortical shell 0.22, breadth 0.17; length of the medullary shell 0.05, breadth 0.04.

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

Subgenus 2. Tholospironium, Haeckel.

Definition.—Spiral convolutions of the cortical shell double; both wings of the sagittal girdle turning around the transverse axis.

4. Tholospira hystrix, n. sp.

Cortical shell covered with numerous (sixty to eighty or more) simple conical spines, about half as long as the shell. Perimeter of the lateral plane hexagonal, one and a half times as long as broad. Four internal kidney-shaped gates, as in Tetrapyle. Both wings of the sagittal girdle turn round one another in two to two and a half double spiral turns.

Dimensions.—Length of the cortical shell 0.21, breadth 0.14; length of the medullary shell 0.04, breadth 0.03.

Habitat.—North Atlantic, Station 354, surface.

5. Tholospira cervicornis, n. sp. (Pl. , fig. 5).

Cortical shell covered with numerous (forty to fifty or more) branched radial spines; each spine antler-shaped, about as long as the medullary Larnacilla-shell, with eight to twelve dichotomous branches (similar to Cromyodrymus abietinus, Pl. , fig. 6). Perimeter of the lateral plane elliptical, one and a third times as long as broad. Four internal kidney-shaped gates, as in Tetrapyle. Both wings of the sagittal girdle turn round one another in one and a half to two double spiral turns.

Dimensions.—Length of the cortical shell 0.2, breadth 0.15; length of the medullary shell 0.03, breadth 0.025.

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

Genus 309. Spironium, n. gen.

Definition.—Lithelida with double, trizonal or Larnacilla-shaped medullary shell; cortical shell subspherical or lentelliptical, constructed of two crossed spirals, which arise from both lateral wings of one girdle (commonly the lateral girdle) and revolve in an opposite diagonal direction around the principal axis.

The genus Spironium differs in a very remarkable manner from all foregoing Lithelida, and is distinguished by a quite peculiar mode of growth. It is most nearly allied to Larcopyle, and may, like this, be derived from Amphipyle (or rather from Larnacilla, beginning to transform into Amphipyle). But whilst in Larcopyle one of the two wings of the lateral girdle overgrows the other in the direction of the transverse axis (turning around the principal axis), here in Spironium both lateral wings begin at the same time to grow out from the lateral sides of the Larnacilla-shaped medullary shell; the most remarkable thing is, however, that the direction of growth in the wings is diverse from the beginning: the left wing grows downwards and turns around the lower (aboral) pole of the principal axis, the right wing grows upwards and turns around the upper (oral) pole of the same axis. Thus both wings of the lateral girdle are crossed in diagonal axes, and with increasing growth one overgrows the other in the direction of these diagonals, so as to resemble the figure 8 in shape. The open gates remaining between the turnings of the girdle become afterwards closed on the surface by irregular lattice-work, and so the whole cortical shell assumes finally a spherical, ellipsoidal, or lentelliptical form. Its surface sometimes becomes covered with simple or branched radial spines. In the interior the eight characteristic egg-shaped gates of Octopyle are commonly (or constantly?) visible, two strong radial beams in the principal axis arising from the poles of the lentelliptical medullary shell.

Subgenus 1. Spironetta, Haeckel.

Definition.—Surface of the shell smooth or rough, but not with radial spines.

1. Spironium octonium, n. sp. (Pl. , fig. 7).

Cortical shell lentelliptical, its breadth (or transverse axis) surpassing considerably the length (or the principal axis). Surface thorny and somewhat hump-backed. The spiral wings of the transverse girdle have about the same breadth as the eight internal gates between them and the axial beams.

Dimensions.—Length of the cortical shell (or principal axis) 0.15, breadth (or transverse axis) 0.2; length of the medullary shell 0.05, breadth 0.04.

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

2. Spironium diagonale, n. sp.

Cortical shell nearly spherical, four times as great as the subspherical medullary shell. Surface rough. The spiral wings of the transverse girdle about half as broad as the eight internal gates between them and the axial beams.

Dimensions.—Diameter of the cortical shell 0.16, of the medullary shell 0.04.

Habitat.—Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms.

Subgenus 2. Spironilla, Haeckel.

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

3. Spironium spinosum, n. sp.

Cortical shell subspherical, five times as great as the subspherical medullary shell. Surface covered with numerous (sixty to eighty or more) simple, bristle-like radial spines, longer than the shell. The spiral wings of the transverse girdle of about the same breadth as the eight internal gates between them and the axial beams.

Dimensions.—Diameter of the cortical shell 0.2, of the medullary shell 0.04.

Habitat.—Pacific, central area, Station 274, surface.

4. Spironium arbustum, n. sp.

Cortical shell lentelliptical, its breadth surpassing its length considerably. Surface covered with numerous (forty to sixty or more) thin radial spines, about as long as the greatest diameter of the shell; each spine with two to six lateral branches, which are either simple or again branched (similar to Cromyodrymus abietinus, Pl. , fig. 6). The spiral wings of the transverse girdle only half as broad as the eight internal gates between them and the strong beams of the principal axis.

Dimensions.—Length of the cortical shell 0.12, breadth 0.15; length of the hexagonal medullary shell 0.05, breadth 0.04.

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