Chapter XI: Literature and History (31)

Commonly between the embracing spiral turnings or convolutions a great number of radial beams is developed, irregularly disposed and often branching; they support the {691}thin spiral lamellæ and give to the whole shell more solidity. Often these beams form imperfect radial septa, by which the spiral cavity of the turnings is divided into a variable number of chambers. But these chambers never become so regular and perfect as in the analogous nautiloid Polythalamia.

In many Lithelida the growth of the shell reaches a certain limit, concluding with the formation of a superficial latticed lamella of lentelliptical or nearly spherical form. In many other forms of the family this seems not to be the case; but these may possibly be younger forms, afterwards reaching the same limit.

The network of the shell in the Lithelida is commonly quite irregular, and so variable that its special conformation has usually no value in the determination of the species. The surface of the shell is often covered with radial spines, which are sometimes arborescent.

The central capsule seems always to preserve the same lentelliptical form (or triaxial ellipsoid) as in all other #Larcoidea#. With the increase of growth it encloses successively a larger part of the spiral cortical shell, but on the outside is constantly protected by the last turnings of the spiral, or by the lattice-lamella of the surface.

_Synopsis of the Genera of Lithelida._

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I. Subfamily Spiremida.
Central medullary shell simple, spherical or lentelliptical.
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Surface of the cortical shell smooth or thorny,
without radial spines, 304. _Spirema_.

Surface of the cortical shell covered with numerous
simple or branched radial spines, 305. _Lithelius_.
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II. Subfamily Larcospirida.
Central medullary shell double, trizonal or _Larnacilla_-shaped.
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The transverse girdle turns around the principal axis, 306. _Larcospira_.

The lateral girdle turns around the sagittal axis, 307. _Pylospira_.

The sagittal girdle turns around the transverse axis, 308. _Tholospira_.

Both wings of the transverse girdle turn around the
principal axis in an opposite diagonal direction, 309. _Spironium_.

Subfamily 1. SPIREMIDA, Haeckel, 1881, Prodromus, p. 464.

_Definition._--#Lithelida# with simple, spherical or subspherical, medullary shell.

Genus 304. _Spirema_,[344] Haeckel, 1881, Prodromus, p. 464.

_Definition._--#Lithelida# with simple, spherical or subspherical, medullary shell, and lentelliptical or subspherical, spirally constructed cortical shell; surface smooth or thorny, without radial spines.

{692}The genus _Spirema_ begins the series of the Spiremida, or of those Lithelida in which the medullary shell presents a simple latticed sphere or ellipsoid, never composed of a double, trizonal or _Larnacilla_-shaped shell. In the present state of our knowledge we cannot say whether this simple medullary shell be a primary formation, or effected by secondary means, by reduction of a double _Larnacilla_-shaped medullary shell, which is constantly found in the Larcospirida. The species of this genus (as of all Lithelida) are difficult to distinguish, are transformistic, and incline very much to variations and abnormalities. The spiral may be simple or double.

Subgenus 1. _Spiremarium_, Haeckel.

_Definition._--Spiral convolutions of the cortical shell simple.

1. _Spirema lentellipsis_, n. sp.

Cortical shell lentelliptical, with smooth surface; proportion of its three dimensive axes = 4 : 5 : 6. In the median plane are visible four perfect turnings of the simple spiral, the breadth of which gradually increases towards the third convolution, finally decreasing; the broadest (third) turning three times as broad as the simple spherical medullary shell.

_Dimensions._--Length of the lentelliptical cortical shell 0.18, breadth 0.15, height 0.12; diameter of the spherical medullary shell 0.02.

_Habitat._--North Atlantic, Station 353, surface.

2. _Spirema melonia_, n. sp. (Pl. 49, fig. 1).

Cortical shell nearly spherical, with smooth surface; proportion of its three dimensive axes = 1.4 : 1.5 : 1.6. In the median plane are visible three perfect turnings of the simple spiral, all of the same breadth as the simple spherical medullary shell; the breadth of each convolution somewhat greater at the poles of the principal than at the poles of the sagittal axis.

_Dimensions._--Length of the shell 0.16, breadth 0.15, height 0.14; medullary shell 0.018.

_Habitat._--Pacific, central area, Station 271, surface.

3. _Spirema flustrella_, Haeckel.

_Flustrella haliomma_, Ehrenberg (1861), Abhandl. d. k. Akad. d. Wiss.
Berlin, 1872, p. 293, Taf. ii. fig. 6.

Cortical shell egg-shaped, with thorny surface; proportion of its three axes = 4 : 5 : 6. In the median plane are visible three perfect turnings of the simple spiral, the first and second of about the same breadth as the simple spherical medullary shell, the third suddenly increasing, and finally three to four times as broad. Network of the surface irregular, with roundish pores.

_Dimensions._--Length of the shell 0.2, breadth 0.17, height 0.14; medullary shell 0.013.

_Habitat._--North Atlantic, Greenland, 1000 fathoms, Ehrenberg; Færöe Channel, John Murray.

{693}Subgenus 2. _Spiremidium_, Haeckel.

_Definition._--Spiral convolutions of the cortical shell double.

4. _Spirema diplospira_, n. sp.

Cortical shell lentelliptical, with smooth surface; proportion of its three dimensive axes = 6 : 7 : 8. In the median plane are visible three perfect turnings of a double spiral, the breadth of which gradually increases; the broadest (third) convolution three times as broad as the simple lentelliptical medullary shell.

_Dimensions._--Length of the shell 0.24, breadth 0.21, height 0.18; medullary shell 0.02.

_Habitat._--Tropical Pacific, Philippines, Station 200, depth 250 fathoms.

5. _Spirema subglobosum_, n. sp.

Cortical shell nearly spherical, with thorny surface; proportion of its three axes = 2 : 2.1 : 2.2. In the median plane are visible two perfect turnings of a double spiral, the breadth of which in the second convolution is four times as great as that of the first convolution and the simple spherical medullary shell.

_Dimensions._--Length of the shell 0.22, breadth 0.21, height 0.2; medullary shell 0.02.

_Habitat._--Tropical Atlantic, off Sierra Leone, Station 348, depth (2450) fathoms.

Genus 305. _Lithelius_,[345] Haeckel, 1862, Monogr. d. Radiol., p. 519.

_Definition._--#Lithelida# with simple, spherical or subspherical, medullary shell, and lentelliptical or subspherical, spirally constructed cortical shell; surface covered with numerous, simple or branched, radial spines.

The genus _Lithelius_, founded by me in 1862, and represented by two Mediterranean species, was at that time the only known form of this family, which now contains six genera and twenty-seven species. It differs from the foregoing _Spirema_ in the possession of numerous radial spines on the surface. These may be either simple or branched. The spiral may be simple or double, and according to this latter modification we distinguish two different subgenera.

Subgenus 1. _Lithospira_, Haeckel.

_Definition._--Spiral convolutions of the cortical shell simple.

1. _Lithelius spiralis_, Haeckel.

_Lithelius spiralis, Haeckel_, 1862, Monogr. d. Radiol., p. 519, Taf.
xxvii. figs. 6, 7.

Cortical shell lentelliptical, one and a third times as long as broad, covered with very numerous (one hundred to one hundred and fifty or more) simple, bristle-shaped radial spines, about as long {694}as the shell. Spiral turnings simple, all nearly of the same breadth and scarcely broader than the simple spherical medullary shell.

_Dimensions._--Length of the cortical shell (with six spiral convolutions) 0.15, breadth 0.13; diameter of the medullary shell 0.012.

_Habitat._--Mediterranean, Messina, Haeckel, surface; Atlantic, Stations 348 to 353, surface.

2. _Lithelius primordialis_, R. Hertwig.

_Lithelius primordialis_, R. Hertwig, 1879, Organism. d. Radiol., p. 54,
Taf. vi. figs. 4, 4_a_.

Cortical shell subspherical, covered with numerous simple, bristle-shaped radial spines, longer than the shell. Spiral turnings simple, with gradually increasing breadth, so that the beginning of the third spiral is twice as broad as the first and as the simple spherical medullary shell.

_Dimensions._--Diameter of the cortical shell (with two spiral convolutions) 0.12; diameter of the medullary shell 0.02.

_Habitat._--Mediterranean, Messina, R. Hertwig, surface.

3. _Lithelius alveolina_, Haeckel, 1862.

_Lithelius alveolina_, Haeckel, 1862, Monogr. d. Radiol., p. 520, Taf.
xxvii. figs. 8, 9.

Cortical shell spherical, covered with simple, very numerous (two hundred to three hundred or more), short, bristle-shaped radial spines, scarcely half as long as the radius of the shell. Spiral turnings simple, with gradually increasing breadth, so that the beginning of the third spiral is three times as broad as the first and as the simple spherical medullary shell.

_Dimensions._--Diameter of the cortical shell (with four spiral convolutions) 0.2; diameter of the medullary shell 0.01.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, on many Stations, surface.

4. _Lithelius capreolus_, n. sp.

Cortical shell lentelliptical, one and a fourth times as long as broad, covered with numerous (eighty to one hundred and twenty or more) short, branched radial spines, about half as long as the radius of the shell; each spine once or twice dichotomous, with curved divergent branches. Spiral turnings simple, with gradually increasing breadth, so that the beginning of the third spiral is twice as broad as the first, and as the simple spherical medullary shell.

_Dimensions._--Length of the cortical shell (with four spiral convolutions) 0.18, breadth 0.14; diameter of the medullary shell 0.015.

_Habitat._--Pacific, central area, Station 274, surface.

Subgenus 2. _Drymospira_, Haeckel, 1881, Prodromus, p. 464.

_Definition._--Spiral convolutions of the cortical shell double.

{695}5. _Lithelius solaris_, n. sp. (Pl. 49, fig. 2).

Cortical shell spherical, covered with simple, very numerous (two hundred to three hundred) bristle-shaped radial spines, longer than the diameter of the shell. Spiral turnings double, both of the same breadth, gradually increasing with the growth of the shell and several times surpassing the diameter of the simple spherical medullary shell. (Pl. 49, fig. 2, exhibits only the first convolutions in the centre of the shell.)

_Dimensions._--Diameter of the cortical shell (with four spiral convolutions) 0.18; diameter of the medullary shell 0.02.

_Habitat._--Pacific, central area, Stations 266 to 272, surface and in various depths.

6. _Lithelius arborescens_, n. sp.

Cortical shell lentelliptical, one and a half times as long as broad, covered with numerous (fifty to eighty or more) branched radial spines, about as long as the greatest diameter of the shell; each spine with two to four lateral branches, which are again branched or dichotomous. Spiral turnings double, both of little different breadth, which increases considerably with the growth of the shell, so that the third turn is four times as broad as the simple spherical medullary shell.

_Dimensions._--Length of the cortical shell (with three spiral convolutions) 0.18, breadth 0.12; diameter of the medullary shell 0.01.

_Habitat._--North Atlantic, Færöe Channel, surface, John Murray.

Subfamily 2. LARCOSPIRIDA, Haeckel.

_Definition._--#Lithelida# with double, trizonal, or _Larnacilla_-shaped medullary shell.

Genus 306. _Larcospira_,[346] 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 {696}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. 49, 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.

{697}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_,[347] 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.

{698}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. 49, 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.

{699}Genus 308. _Tholospira_,[348] 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 {700}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. 49, 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. 49, 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. 30, 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.

{701}Genus 309. _Spironium_,[349] 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. 49, 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.

{702}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. 30, 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.

Family XXX. #STREBLONIDA#, n. fam. (Pl. 49, figs. 8, 9).

_Definition._--#Larcoidea# with asymmetrical, spiral, polythalamous shell, composed of a variable number of roundish chambers, which form together an ascending spiral; both halves of the shell unequal. Primordial chamber either simple or _Larnacilla_-shaped.

The family #Streblonida# comprises those #Larcoidea# in which a number of chambers is arranged in an ascending spiral, round a simple or trizonal primordial chamber, like winding stairs. They show the same spiral structure as in the foregoing {703}family, but whilst in the Lithelida the spiral line lies in one plane (as in _Nautilus_), in the Streblonida it ascends like a screw (as in _Helix_). Therefore the former have the same relation, regarding the spiral structure, to the nautiloid Polythalamia as the latter to the turbinoid Foraminifera. Indeed the single forms of Streblemida repeat in their special structure the characteristic genera of Turbinoida, such as _Globigerina_, _Rosalina_, _Pulvinulina_, _Hastigerina_, &c. As in these calcareous turbinoid Foraminifera, so also in the analogous siliceous Streblonida the distinction of species is very difficult and open to many objections.

The number of species in this family is very small; all are rare and for the most part very opaque and difficult to understand, so that the following distinction of a dozen species can have only a provisional value. To get a complete idea of their peculiar structure, the shell must be turned and observed from different sides, and thus their full study requires yet much time and work. There are to be found evident transitional forms between them and the Lithelida on the one hand and the Soreumida on the other. Besides this, most species of Streblonida seem to have more inclination to individual varieties and abnormalities than the majority of the other Radiolaria.

The general form of the whole shell is in the Streblonida sometimes more egg-shaped or even subspherical, at other times more top-like or conical, sometimes nearly discoidal. The height of the shell (or the vertical axis of the ascending spiral) is occasionally larger, at other times smaller than the breadth (or the greatest horizontal diameter, perpendicular to the height). Some very flat forms seem to approach the Lithelida. With regard to the internal screw-formation, the shell of all Streblonida is asymmetrical.

The number of the aggregated incomplete chambers is commonly between ten and twenty, but ascends sometimes to thirty, forty, or more. Sometimes the size of all the chambers is nearly the same, sometimes they increase gradually, occasionally also very rapidly. The primordial chamber (or the first and oldest) seems to be commonly the smallest, and inversely, the last and youngest chamber, the largest. But sometimes (in _Streblopyle_) also the contrary may be the case. The form of the single chambers is very variable, from the spherical or hemispherical through all transitions leading to irregular roundish or longish forms. The network is commonly irregular, with small roundish pores of different sizes, but sometimes also regular, circular. The surface of the shell is commonly smooth or rough, rarely covered with radial spines. In most species the reticulation and particularly the separation of the chambers is more or less incomplete.

As in the Lithelida, so also in the Streblonida we can distinguish two subfamilies. In the Streblacanthida (_Streblonia_, _Streblacantha_) the primordial chamber is a simple, spherical, subspherical, or lentelliptical latticed shell. In the Streblopylida (_Streblopyle_) the primordial chamber is trizonal or _Larnacilla_-shaped, as in the greater number of #Larcoidea#, composed of three elliptical latticed girdles of unequal size, perpendicular one to another, and surrounding a simple central chamber. As in the Lithelida, so also {704}here we cannot certainly say whether the former have originated from the latter by reduction of the _Larnacilla_-shell, or whether both groups be of different origin. The latter is perhaps more probable. This family as well as the foregoing requires a much more careful study than I could give to it.

_Synopsis of the Genera of Streblonida._

-------------------------------------------------------------------------
I. Subfamily Streblacanthida.
Primordial chamber simple, spherical or lentelliptical.
-------------------------------------------------------------------------
Shell without radial spines, 310. _Streblonia_.

Shell with radial spines, 311. _Streblacantha_.
-------------------------------------------------------------------------
II. Subfamily Streblopylida.
Primordial chamber trizonal or _Larnacilla_-shaped.
-------------------------------------------------------------------------
Shell without radial spines, 312. _Streblopyle_.

Genus 310. _Streblonia_,[350] n. gen.

_Definition._--#Streblonida# with simple, spherical, subspherical, or lentelliptical primordial chamber, beginning the screw-like series of spirally ascending chambers. Surface smooth or thorny, without radial spines.

The genus _Streblonia_ contains those Streblonida in which a variable number of roundish, subspherical, or longish chambers form a screw-like aggregate, beginning with a quite simple primordial chamber. The special order of the complex spiral offers interesting resemblances to different genera of the calcareous Foraminifera, from which I have taken the corresponding name of the species. The whole form of the shell is sometimes more egg-shaped or subspherical, at other times more top-like or conical, occasionally very flat. Its surface is smooth or rough, but not covered with radial spines.

1. _Streblonia globigerina_, n. sp.

Shell subspherical, thick walled, clustered, with eight to ten nearly spherical chambers, of rapidly increasing size, the tenth chamber about twelve times as broad as the first. Breadth of the shell nearly equal to the height. Pores subregular, circular, hexagonally formed, of about the same breadth as the bars; about sixteen on the breadth of the tenth chamber. (Resembles very much the common _Globigerina_.)

_Dimensions._--Breadth of the shell 0.18, height 0.16.

_Habitat._--North Pacific, Station 253, depth 3125 fathoms.

2. _Streblonia uvigerina_, n. sp.

Shell nearly egg-shaped, clustered, with eight to eleven subspherical chambers of gradually increasing size, the tenth chamber about six times as broad as the first. Breadth of the shell about {705}half its height. Pores of the shell subregular, circular, about twice as broad as the bars; about twenty on the breadth of the tenth chamber. (Resembles some species of _Uvigerina_.)

_Dimensions._--Breadth of the shell 0.11, height 0.23.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

3. _Streblonia polymorphina_, n. sp.

Shell egg-shaped, thin walled, with twelve to fourteen roundish chambers of rapidly increasing size, the tenth chamber about seven times as broad as the first. Breadth of the shell about two-thirds of the height. Pores irregular roundish, twice as broad as the bars; about twenty on the tenth chamber. (Resembles certain forms of _Polymorphina_.)

_Dimensions._--Breadth of shell 0.22, height 0.14.

_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms.

4. _Streblonia bulimina_, n. sp.

Shell nearly egg-shaped, thick walled, clustered, with fourteen to eighteen egg-shaped chambers of rapidly increasing size, the tenth chamber about eight times as broad as the first. Breadth of the shell about two-thirds of the height. Pores irregular, roundish, half as broad as the bars; about twelve on the breadth of the tenth chamber. (Resembles closely _Bulimina_.)

_Dimensions._--Breadth of the shell 0.17, height 0.24.

_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.

5. _Streblonia rosalina_, n. sp.

Shell top-shaped or flatly conical, with twelve to sixteen chambers of gradually increasing size, the tenth chamber about four times as broad as the first. Breadth of the shell twice as large as the height. Pores subregular, circular, very small, of the same breadth as the bars; about twelve on the breadth of the tenth chamber. (Resembles some forms of _Rosalina_.)

_Dimensions._--Breadth of the shell 0.27, height 0.13.

_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms.

6. _Streblonia planorbulina_, n. sp.

Shell very flatly conical, nearly lenticular or discoidal, with twenty to twenty-five chambers of nearly equal size, the tenth chamber a little broader than the first. Breadth of the shell exceeds five to six times the height. Pores subregular, circular, very small, half as broad as the bars; about eight on the breadth of the tenth chamber. (Resembles closely _Planorbulina_.)

_Dimensions._--Breadth of the shell 0.3 to 0.4, height 0.06 to 0.07.

_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms.

{706}7. _Streblonia pulvinulina_, n. sp.

Shell top-shaped or flatly conical, with thirty to forty chambers of slowly increasing size, the tenth chamber about three times as broad as the first. Breadth of the shell exceeds three times the height. Pores circular, subregular, very small, about one-third as broad as the bars; about thirty in the breadth of the tenth chamber. (Resembles closely _Pulvinulina_.)

_Dimensions._--Breadth of the shell 0.25, height 0.08.

_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms.

Genus 311. _Streblacantha_,[351] n. gen.

_Definition._--#Streblonida# with simple, spherical, subspherical, or lentelliptical primordial chamber, beginning the screw-like series of spirally ascending chambers. Surface covered with radial spines.

The genus _Streblacantha_ differs from the nearly allied _Streblonia_ only in the covering of radial spines, and bears therefore the same relation to it as _Hastigerina_ has to _Globigerina_ amongst the similar calcareous Polythalamia.

1. _Streblacantha siderolina_, n. sp. (Pl. 49, figs. 8, 8_a_).

_Streblonia siderolina_, Haeckel, 1883, MS.

Shell flatly conical, with fourteen to sixteen nearly hemispherical chambers of gradually increasing size, the tenth chamber about six times as broad as the first. Breadth of the shell nearly equal to the height. Pores subregular, circular, hexagonally framed, twice as broad as the bars; about nine pores on the breadth of the tenth chamber. Surface covered with numerous short conical radial spines, one-fourth to one-sixth as long as the diameter of the shell.

_Dimensions._--Breadth of the shell 0.15, height 0.17.

_Habitat._--South Pacific, Station 298, depth 2225 fathoms.

2. _Streblacantha calcarina_, n. sp.

Shell conical, with sixteen to eighteen roundish chambers of gradually increasing size, the tenth chamber about three times as broad as the first. Breadth of the shell about one and a half times the height. Pores irregular, roundish. Surface covered with numerous strong conical radial spines, about half as long as the diameter of the shell.

_Dimensions._--Breadth of the shell 0.24, height 0.17.

_Habitat._--South Pacific, Station 285, depth 2375 fathoms.

{707}3. _Streblacantha hastigerina_, n. sp.

Shell nearly spherical, clustered, with nine to eleven nearly spherical chambers of rapidly increasing size, the tenth chamber about six times as broad as the first. Breadth of the shell nearly equal to the height. Pores subregular, circular, of about the same breadth as the bars. Surface bristly, covered with numerous very thin and long, needle-shaped radial spines, longer than the diameter of the shell. (Resembles closely _Hastigerina_.)

_Dimensions._--Breadth of the shell 0.18, height 0.15.

_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms.

Genus 312. _Streblopyle_,[352] n. gen.

_Definition_.--#Streblonida# with trizonal lentelliptical medullary shell (composed like _Larnacilla_ of three elliptical dimensive girdles surrounding one simple central primordial chamber). From this begins a screw-like series of spirally ascending chambers. Surface smooth or thorny, without radial spines.

The genus _Streblopyle_ presents externally the same appearance and contour as _Streblonia_, and is composed like this of a variable number of chambers, ascending screw-like around the axis of the spiral shell. The first or primordial chamber, however, in which the growth begins, is in _Streblonia_ a simple spherical shell, but in _Streblopyle_ a trizonal shell or _Larnacilla_-shell (compare above, p. 600). The chambers are very incompletely separated, and comparatively much larger, their number much smaller than in _Streblonia_. The structure in the species of this genus is difficult to understand.

1. _Streblopyle helicina_, n. sp. (Pl. 49, fig. 9).

Shell helicoid, one and a third times as high as broad, with eight to twelve incomplete semizonal chambers, ascending spirally from the lateral half girdle of the lentelliptical medullary shell, octopyle-shaped, and enveloping it in three to four spiral turnings. The height of the whole cortical shell equals nearly five times the height of the trizonal medullary shell. Pores irregular, roundish. Surface of the shell rough or nearly smooth. (This species seems to be nearly allied to _Spironium octonium_.)

_Dimensions._--Breadth of the spiral cortical shell 0.18, height 0.24; breadth of the medullary shell 0.04, height 0.05.

_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms.

2. _Streblopyle spirulina_, n. sp.

Shell egg-shaped or nearly spherical, about as high as broad, with eight to nine semizonal chambers, ascending spirally from the subspherical trizonal medullary shell, and enveloping it in {708}four to five turnings. The sixth chamber twice as broad as the trizonal medullary shell. Pores irregular, roundish. Surface of the shell thorny.

_Dimensions._--Breadth of the spiral cortical shell 0.27, height 0.25; breadth of the medullary shell 0.05, height 0.06.

_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.

Family XXXI. #PHORTICIDA#, Haeckel (Pl. 49, figs. 10, 11).

_Phorticida_, Haeckel, 1881, Prodromus, p. 464.

_Definition._--#Larcoidea# with quite irregular monothalamous shell, representing irregular modifications of an original lentelliptical latticed shell; the irregular cortical shell encloses a regular or subregular, lentelliptical or trizonal medullary shell.

The family Phorticida comprises a small number of #Larcoidea# in which a subregular, trizonal, lentelliptical medullary shell is enclosed by an irregular simple or spongy cortical shell. The lattice-work of the latter is sometimes simple and complete, at other times incomplete, with open gates (as in the Pylonida), sometimes also spongy. Its form is always more or less irregular, roundish, often dimply or tuberous; different from most other #Larcoidea#.

The medullary shell is constantly a regular or subregular _Larnacilla_-shell, composed of three elliptical latticed girdles of different sizes, perpendicular one to another. This leaves no doubt that the Phorticida are true #Larcoidea#. The connection of it with the cortical shell is rarely effected by radial beams, commonly by two opposite latticed wings, which are identical with the lateral halves of the transverse girdle in the Pylonida diplozonaria (_Amphipyle_, _Tetrapyle_). Often also between this transverse and a second (lateral) girdle there remain large open gates, so that the affinity between these Phorticida and the Pylonida cannot be doubted. In other cases these gates become closed, so that they more nearly approach the Larnacida. From both families they differ by the irregularity of the papillate or tuberous cortical shell. The network is more or less irregular, its surface often thorny, but never covered with symmetrically disposed radial spines.

The central capsule is lentelliptical, encloses the medullary shell, and is enveloped by the cortical shell, as in the nearly allied Pylonida and Larnacida, of which the Phorticida may be regarded as irregular aberrant forms.

_Synopsis of the Genera of Phorticida._

Cortical shell simply latticed, 313. _Phorticium_.

Cortical shell spongy, 314. _Spongophortis_.

{709}Genus 313. _Phorticium_,[353] Haeckel, 1881, Prodromus, p. 464.

_Definition._--#Phorticida# with irregular cortical shell of simple lattice-work, enclosing a lentelliptical _Larnacilla_-shaped medullary shell.

The genus _Phorticium_ comprises all Phorticida in which the irregular cortical shell is formed by simple lattice-work, not by spongy framework. We can divide this genus into two subgenera: in _Phortopyle_ (as in the _Pylonida_) the lattice-work of the cortical shell exhibits large openings or gates; in _Phortolarcus_ these gates are perfectly closed by network; the former may be regarded as abnormal or irregular Pylonida, the latter as modifications of Larnacida.

Subgenus 1. _Phortopyle_, Haeckel.

_Definition._--Lattice-work of the irregular cortical shell incomplete, with large openings or gates.

1. _Phorticium pylonium_, n. sp. (Pl. 49, fig. 10).

Cortical shell irregular, roundish, about three times as large as the enclosed lentelliptical, regular, _Larnacilla_-shell, connected with it by some radial beams and irregularly latticed girdles; between these remain four to eight large open gates of irregular roundish form and size; and these gates are the same as in _Tetrapyle_ and _Octopyle_. This very variable species may be regarded as a monstrosity of those genera of Pylonida; it is very common, but all individuals are more or less unequal; some specimens approach to some common species of _Tetrapyle_. The surface of the shell is more or less spiny.

_Dimensions._--Diameter of the irregular cortical shell 0.12 to 0.18; length of the lentelliptical medullary shell 0.05 to 0.06, breadth 0.035 to 0.045.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, &c., common, surface and in various depths.

2. _Phorticium spironium_, n. sp.

Cortical shell irregular, roundish, tuberous, about four times as large as the enclosed subregular _Larnacilla_-shell, connected with it by some irregular radial beams, and by opposite, spirally begining, irregularly latticed girdles, comparable to those of _Spironium_; between them remain six to twelve large open gates of irregular size and form. Surface rough. The resemblance to some forms of _Spironium_ makes it probable that this species is a deformity or monstrosity of that genus.

_Dimensions._--Diameter of the irregular cortical shell 0.12 to 0.2, of the lentelliptical medullary shell 0.03 to 0.06.

_Habitat._--Pacific, central area, Stations 270 to 274, surface, and in various depths.

{710}Subgenus 2. _Phortolarcus_, Haeckel.

_Definition._--Lattice-work of the irregular cortical shell complete, without large openings or gates.

3. _Phorticium deforme_, n. sp.

Cortical shell irregular, roundish or longish, three times as large as the enclosed subregular, lentelliptical _Larnacilla_-shell, connected with it by two opposite latticed wings (the halves of the transverse girdle of _Tetrapyle_). Network of the cortical shell irregular, dense, perfectly closed, without larger openings or gates. Surface thorny. (May be regarded as a monstrous form of _Larnacalpis_.)

_Dimensions._--Diameter of the irregular cortical shell 0.15 to 0.18, of the medullary shell 0.04 to 0.06.

_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.

4. _Phorticium abnorme_, n. sp.

Cortical shell irregular, roundish, tuberous, with five to ten quite irregular or nearly hemispherical protuberances, which resemble the cupolas of Zonarida. The regular lentelliptical _Larnacilla_-shell is one-third to one-fourth as large as the enclosing cortical shell, and is connected with it by some irregular radial beams. Lattice-work completely closed, without gates. Surface spiny. (May be regarded as an anomalous form of _Zonidium_; as in the other species of this variable genus, the individuals are very unequal.)

_Dimensions._--Diameter of the irregular cortical shell 0.12 to 0.2, of the medullary shell 0.03 to 0.05.

_Habitat._--Atlantic and Pacific, tropical zone, surface, and at various depths.

Genus 314. _Spongophortis_,[354] Haeckel, 1881, Prodromus, p. 464.

_Definition._--#Phorticida# with irregular cortical shell of spongy framework, enclosing a lentelliptical _Larnacilla_-shaped medullary shell.

The genus _Spongophortis_ differs from _Phorticium_ in the spongy framework of the cortical shell. This encloses the inner _Larnacilla_-shaped medullary shell either directly, or both shells are separated by a hollow interval, and connected either by radial beams or by latticed lamellæ. Perhaps both these subgenera might be better separated as genera.

{711}Subgenus 1. _Stypophorticium_, Haeckel.

_Definition._--Spongy cortical shell immediately enclosing the lentelliptical medullary shell, without hollow interval.

1. _Spongophortis spongiosa_, n. sp.

Cortical shell irregular, roundish, rough or tuberous, composed of loose spongy framework, which immediately envelops the lentelliptical central _Larnacilla_-shell; the diameter of the former becomes about five to six times as large as that of the latter.

_Dimensions._--Diameter of the spongy cortical shell 0.15 to 0.25, of the trizonal medullary shell 0.03 to 0.04.

_Habitat._--Pacific, central area, Station 274, surface.

Subgenus 2. _Spongophorticium_, Haeckel.

_Definition._--Spongy cortical shell separated by a hollow interval from the lentelliptical medullary shell.

2. _Spongophortis radiosa_, n. sp.

Cortical shell irregular, roundish, four to five times as large as the enclosed lentelliptical _Larnacilla_-shell, with which it is connected by ten to twenty irregularly disposed radial beams. Spongy framework compact, about as thick as the medullary shell. Surface covered with numerous short, bristle-shaped, radial spines.

_Dimensions._--Diameter of the spongy cortical shell 0.15 to 0.2, of the trizonal medullary shell 0.035 to 0.045.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

3. _Spongophortis larnacilla_, n. sp. (Pl. 49, figs. 11_a_-11_d_).

Cortical shell irregular, roundish, tuberous, three to four times as large as the enclosed lentelliptical _Larnacilla_-shell, connected with it by two opposite latticed wings (the halves of the transverse girdle of _Tetrapyle_). Spongy framework compact, about half as thick as the medullary shell. Surface rough. (May be regarded as an abnormal _Tetrapyle_ or _Larnacalpis_, with an irregular spongy cortical shell.)

_Dimensions._--Diameter of the spongy cortical shell 0.16 to 0.2, of the trizonal medullary shell 0.04 to 0.06.

_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms.

{712}Family XXXII. #SOREUMIDA#, Haeckel (Pl. 49, figs. 12, 13).

_Soreumida_, Haeckel, 1881, Prodromus, p. 464.

_Definition._--#Larcoidea# with quite irregular polythalamous shell, composed of a variable number of chambers, aggregated without any definite order. Primordial chamber either simple or _Larnacilla_-shaped.

The family #Soreumida# contains a small number of #Larcoidea#, different from most other #Sphærellaria# in the complete irregularity of the polythalamous shell, which is composed of a variable number of roundish chambers or subspherical latticed shells, aggregated in the form of an irregular heap. We can distinguish in this family only two genera, with very different structure of the central medullary shell or the first chamber beginning the growth; and these correspond to the two subfamilies of the nearly allied Streblonida (p. 704). In _Soreuma_ (as in _Streblonia_) the first or primordial chamber, from which the growth begins, is like the others, a simple spherical or irregular roundish lattice-shell. In _Sorolarcus_, however (as in _Streblopyle_), the first or primordial chamber is a trizonal or _Larnacilla_-shell. It is not improbable that the former originated phylogenetically from _Streblonia_, the latter from _Streblopyle_, by loss of the original spiral order of growth. But it is also possible that these groups have no nearer relation. Among the calcareous Foraminifera a very similar form is represented by _Acervulina_ and its allies.

The general form of the whole shell in the Soreumida is sometimes more egg-shaped or lentelliptical, at other times even subspherical, occasionally quite irregular, tuberous, or clustered. The number of the aggregated chambers is very variable, in _Sorolarcus_ between ten and thirty, in _Soreuma_ ascending to fifty to eighty, sometimes from one hundred to one hundred and fifty and more. Their size is sometimes nearly equal, at other times very different, their form commonly very irregular, roundish, but sometimes also subspherical or egg-shaped. The network of the shell is also commonly irregular, with roundish pores of different sizes. The surface is usually smooth or rough, rarely covered with radial spines.

The central capsule is not known, as I observed only a few skeletons of this family.

_Synopsis of the Genera of Soreumida._

Primordial chamber of the shell simple, subspherical
or roundish, 315. _Soreuma_.

Primordial chamber of the shell trizonal or
_Larnacilla_-shaped, 316. _Sorolarcus_.

Genus 315. _Soreuma_,[355] Haeckel, 1881, Prodromus, p. 464.

_Definition._--#Soreumida# with numerous chambers, aggregated without any regularity around one simple, spherical or subspherical, central chamber.

{713}The genus _Soreuma_ contains those Soreumida in which no trace of any regular structure is found, but all the chambers of the irregular shell are without any order, aggregated around a simple spherical or subspherical central chamber or medullary shell. _Soreuma_ may have originated either from _Sorolarcus_ by loss of the central _Larnacilla_-shell or from _Cenolarcus_ by irregular apposition of new chambers around the lentelliptical central chamber or simple Larcoid-shell. Some species seem to exhibit a transition to _Sorolarcus_. Owing to the absolute irregularity of the polythalamous shell _Soreuma_ resembles _Acervulina_ among the Foraminifera.

Subgenus 1. _Soreumium_, Haeckel.

_Definition._--Shell without radial spines.

1. _Soreuma irregulare_, n. sp. (Pl. 49, fig. 12).

Shell irregular, clustered, or tuberous, composed of a large number (one hundred and twenty to one hundred and fifty or more) of irregular, roundish chambers of very different sizes, the largest four to five times as broad as the smallest. Network very delicate, with very small roundish pores, to five times as broad as the bars. Surface thorny.

_Dimensions._--Diameter of the shell 0.3, of the single chambers 0.02 to 0.08.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.

2. _Soreuma acinosum_, n. sp.

Shell irregularly lentelliptical, with different growth in the three dimensions, composed of a large number (forty to sixty or more) of irregular, roundish chambers of very different sizes, the largest six to eight times as broad as the smallest. Pores subregular, circular, twice as broad as the bars. Surface smooth.

_Dimensions._--Length of the shell 0.21, breadth 0.17, height 0.13; diameter of the largest chambers 0.03, of the smallest 0.004.

_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms.

3. _Soreuma subglobosum_, n. sp.

Shell nearly spherical, composed of a variable number (twelve to fifteen or more) of irregularly aggregated subspherical chambers of nearly equal size. Pores subregular, circular, twice as broad as the bars. Surface thorny.

_Dimensions._--Diameter of the shell 0.25, of the largest chambers 0.04, of the smallest 0.005.

_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms.

{714}4. _Soreuma acervulina_, n. sp.

Shell quite irregular, cloddy, or tuberous, composed of twenty to thirty (or more) roundish chambers of almost uniform size, the largest twice to three times as broad as the smallest. Pores irregular, roundish. Surface smooth.

_Dimensions._--Diameter of the shell 0.18 to 0.24, of the largest chambers 0.06, of the smallest 0.02.

_Habitat._--South Pacific, Station 295, depth 1500 fathoms.

Subgenus 2. _Soreumidium_, Haeckel.

_Definition._--Shell with radial spines.

5. _Soreuma spinosum_, n. sp.

Shell quite irregular, cloddy, or tuberous, composed of thirty to forty subspherical chambers of nearly the same size. Pores subregular, circular, twice as broad as the bars; on the equator of each chamber six to eight pores. Surface thorny, covered with irregularly scattered conical radial spines, about as long as the diameter of the chambers.

_Dimensions._--Diameter of the shell 0.17 to 0.25, of the chambers 0.04.

_Habitat._--North Pacific, Station 241, depth 2300 fathoms.

6. _Soreuma setosum_, n. sp.

Shell nearly spherical, composed of sixty to seventy (or more) irregular, roundish chambers of very different sizes, the largest five to six times as broad as the smallest. Pores irregular, roundish. Surface bristly, covered with very numerous, long and thin, bristle-shaped radial spines, about as long as the diameter of the shell.

_Dimensions._--Diameter of the shell 0.28, of the chambers 0.005 to 0.03.

_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms.

Genus 316. _Sorolarcus_,[356] n. gen.

_Definition._--#Soreumida# with numerous chambers, aggregated irregularly around a trizonal medullary shell or _Larnacilla_-shell.

The genus _Sorolarcus_ comprises those Soreumida in which the heap of irregularly aggregated chambers encloses a central trizonal medullary shell, by which they demonstrate clearly their descent from Larnacida or Pylonida. The lentelliptical medullary {715}shell exhibits quite the same characteristic structure as that of _Larnacilla_, being composed of three elliptical latticed girdles, perpendicular one to another. In some species also the beginning of a second system of girdles is clearly indicated, so that there can be no doubt as to their derivation from _Amphipyle_ or _Tetrapyle_.

Subgenus 1. _Sorolarcium_, Haeckel.

_Definition._--Shell without radial spines.

1. _Sorolarcus larnacillifer_, n. sp. (Pl. 49, fig. 13).

Shell irregular, clustered, or tuberous, composed of twenty to thirty irregular, roundish chambers of very different size, the largest four to eight times as broad as the smallest, aggregated without order around a central, lentelliptical, _Larnacilla_-shaped medullary shell. Pores irregular, roundish, twice to four times as broad as the bars. Surface smooth or a little spiny.

_Dimensions._--Diameter of the whole shell 0.18, of the central _Larnacilla_-shell 0.05.

_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms.

2. _Sorolarcus tetrapylifer_, n. sp.

Shell irregularly roundish, clustered, composed of ten to twelve irregular rather long chambers of almost uniform size, the largest twice as broad as the smallest, aggregated without order around a central shell of the structure of _Tetrapyle_, which encloses an inner trizonal _Larnacilla_-shell of half the size. Pores irregular, roundish, twice to four times as broad as the bars. Surface spiny.

_Dimensions._--Diameter of the whole shell 0.25, of the outer (_Tetrapyle_-like) medullary shell 0.12, of the inner (_Larnacilla_-like) shell 0.06.

_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.

Subgenus 2. _Sorolarcidium_, Haeckel.

_Definition._--Shell with radial spines.

3. _Sorolarcus terminalis_, n. sp.

Shell nearly spherical, composed of fifteen to eighteen irregularly aggregated roundish chambers of nearly equal size; in the centre a lentelliptical _Larnacilla_-shell. Surface covered with numerous thin, bristle-like radial spines, somewhat longer than the shell.

_Dimensions._--Diameter of the whole shell 0.21, of the central _Larnacilla_-shell 0.05.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.

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LEGION II. #ACANTHARIA#,

VEL ACTIPYLEA, VEL ACANTHOMETREA (PLS. 129-140).

_Acantharia_, Haeckel, 1881.
_Actipylea_, Haeckel, 1882.
_Acanthometrea_, Hertwig, 1879.
_Panacantha_, Haeckel, 1878.

_Definition._--Radiolaria with simple membrane bounding the central capsule, which is everywhere perforated by innumerable fine pores (disposed either equally or symmetrically). Extracapsulum without phæodium. Skeleton centrogenous (its growth proceeding from the centre), acanthinic (organic, not siliceous). Fundamental form originally spherical.

The legion ACANTHARIA vel ACTIPYLEA, to the extent here defined, was constituted by me, 1878, in my Protistenreich (p. 102) under the name "PANACANTHA." A more accurate definition of this group was given in 1879 by Hertwig under the name ACANTHOMETREA. Both names were replaced by me, 1881, in my Prodromus (pp. 421, 465) by the more convenient name ACANTHARIA. This legion comprises all those Radiolaria which were first described by Johannes Müller, 1858, as _Acanthometrae_, and also an important part of his _Haliomma_. In my Monograph (1862, pp. 371-424) I disposed them in three families, Acanthometrida, Diploconida, and Dorataspida.