Family XXXII. Soreumida, Haeckel (Pl. , 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. ). 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, Haeckel, 1881, Prodromus, p. 464.

Definition.—Soreumida with numerous chambers, aggregated without any regularity around one simple, spherical or subspherical, central chamber.

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. , 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.

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, 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 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. , 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.