Subfamily 2. Trematodiscida, Haeckel, 1862, Monogr. d. Radiol., p. 491 ( sensu emendato et restricto )

Definition.—Porodiscida without radial appendages of the disk (solid spines or chambered arms on the margin), and without peculiar oscula on the margin of the disk, which is composed of two to four or more concentric rings.

Genus 214. Porodiscus, Haeckel, 1881, Prodromus, p. 459.

Definition.—Porodiscida with simple circular disk, composed of several rings (without radial appendages or peculiar oscula on the margin of the disk).

The genus Porodiscus is, next to its ancestral form, Archidiscus, the simplest and most primitive form of the Porodiscida, from which all other genera of this family can be derived. The disk is quite simple, without any marginal appendages, composed of a variable number of rings, commonly of circular form, sometimes more or less polygonal, elliptical, or irregular. In my Monograph (1862, pp. 491, 513) I had separated the species, here united in Porodiscus, into two different genera: Trematodiscus with concentric rings, and Discospira with spiral rings. But the extended study of these very common forms in a great number of specimens in the Challenger collection has convinced me that the separation of those two genera cannot be maintained. In one and the same locality, where one single characteristic disk-form is very common, we find intermingled quite regular disks with only concentric, circular rings (Trematodiscus), and other disks with one single perfect spiral ring (Discospira); and between these a smaller number of specimens, in which the rings of the disk are partly concentric, partly spiral; either the rings of the central part of the disk are concentric, the outer spiral (Perispira), or the proportion is inverse (Centrospira); and sometimes the whole disposition of the concentric and spiral rings is irregular, and the rings often interrupted (Atactodiscus). Therefore it appears more natural to give to all these different forms only the value of subgenera of Porodiscus, as I have already proposed in my Prodromus (1881, p. 459). Even the numerous species of Porodiscus (mainly characterised by the equal or different breadth of the rings, and by the number, form, and size of the connecting radial beams and of the superficial pores) are for the most part very variable and hard to distinguish, as all those characters are not constant. Porodiscus is a quite "transformistic genus."

Subgenus 1. Trematodiscus, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 841.

Definition.—All rings of the disk concentric (commonly circular, rarely a little elliptical or polygonal).

1. Porodiscus orbiculatus, Haeckel.

Trematodiscus orbiculatus, Haeckel, 1862, Monogr. d. Radiol., p. 492, Taf. xxix. fig. 1.

Trematodiscus orbiculatus, Stöhr, 1880, Palæontogr., vol. xxvi. p. 108.

All rings of the disk circular, concentric, of equal breadth, connected by numerous alternating radial beams. Chambers differing little in size, about as large as the central chamber. Pores regular, circular, two to two and a half on the breadth of each ring.

Dimensions.—Diameter of the disk (with nine rings) 0.18; breadth of each ring 0.01; pores 0.003.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface; also fossil in Tertiary rocks of Barbados, Sicily, and Nicobar.

2. Porodiscus concentricus, Haeckel.

Trematodiscus concentricus, Haeckel, 1862, Monogr. d. Radiol., p. 493.

Trematodiscus concentricus, Stöhr, 1880, Palæontogr., vol. xxvi. p. 108.

Flustrella concentrica, Ehrenberg, 1838, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 132; Ibid., 1875, p. 72, Taf. xxii. fig. 13.

? Flustrella concentrica, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 61, Taf. xx. fig. 42, Taf. xxi. fig. 51, Taf. xxxvi. fig. 29.

All rings of the disk circular, concentric, of equal breadth, connected by numerous piercing radial beams. Chambers different in size, increasing from the centre towards the periphery. Pores regular, circular, one and half to two on the breadth of each ring.

Dimensions.—Diameter of the disk (with eight rings) 0.16; breadth of each ring 0.01; pores 0.003.

Habitat.—Fossil in many Tertiary rocks—Barbados, Sicily, Greece, &c.

Porodiscus haeckelii = Trematodiscus haeckelii, Bütschli, 1882, L. N. , Taf. xxiv. figs. 5a, 5b.

3. Porodiscus flustrella, n. sp. (Pl. , fig. 1).

Trematodiscus flustrella, Haeckel, 1866, MS. Canar. Ins.

All rings of the disk circular, concentric, of equal breadth, connected by numerous piercing radial beams. Chambers different in size, increasing from the centre towards the periphery. Pores very irregular, polygonal, or roundish, one to three on the breadth of each ring.

Dimensions.—Diameter of the disk (with six rings) 0.12; breadth of each ring 0.01; pores 0.002 to 0.006.

Habitat.—Cosmopolitan; Atlantic, Pacific, &c., many Stations, surface.

4. Porodiscus sorites, Haeckel.

Trematodiscus sorites, Haeckel, 1862, Monogr. d. Radiol., p. 492, Taf. xxix. fig. 2.

All rings of the disk circular, concentric, of equal breadth, connected by numerous alternating radial beams. Chambers different in size, increasing from the centre. Pores regular, circular, one to one and a half on the breadth of each ring.

Dimensions.—Diameter of the disk (with six rings) 0.12; breadth of each ring 0.01; pores 0.006.

Habitat.—Mediterranean (Messina), surface.

5. Porodiscus macroporus, Haeckel.

Trematodiscus macroporus, Haeckel, 1879, MS.

Flustrella macropora, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 160.

All rings of the disk circular, concentric, of equal breadth, connected by numerous piercing radial beams. Chambers of different breadth, increasing from the centre. Pores regular, very large, nearly square, one single pore on the breadth of each ring.

Dimensions.—Diameter of the disk (with five rings) 0.11; breadth of each ring 0.01; pores 0.005.

Habitat.—Fossil in the Tertiary rocks of Barbados.

6. Porodiscus microporus, Haeckel.

Trematodiscus microporus, Stöhr, 1880, Palæontogr., vol xxvi. p. 108, Taf. iv. fig. 17.

All rings of the disk concentric, either circular or a little elliptical; the innermost rings of the same breadth as the central chamber, the third ring much broader. Radial beams between them alternating; chambers of different size. Pores very small, subregular, everywhere of the same size, four to five pores on the breadth of each ring.

Dimensions.—Diameter of the disk (with three rings) 0.15; breadth of the inner rings 0.02, of the outer 0.03; pores 0.0016.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

7. Porodiscus ellipticus, Haeckel.

Trematodiscus ellipticus, Stöhr, 1880, Palæontogr., vol. xxvi. p. 108, Taf. iv. fig. 16.

All rings of the disk concentric, either circular or a little elliptical, connected by eight piercing radial beams; central chamber elliptical, of the same breadth as the first ring, broader than the following rings, the breadth of which decreases towards the periphery. Pores irregular, in the inner rings twice as broad as in the outer (third) ring, four to five on the breadth of each ring.

Dimensions.—Diameter of the disk (with three rings) 0.18; breadth of the inner rings 0.03, of the outer 0.02; pores 0.003 to 0.006.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

8. Porodiscus heterocyclus, Haeckel.

Trematodiscus heterocyclus, Haeckel, 1862, Monogr. d. Radiol., p. 493, Taf. xxix. fig. 3.

? Flustrella cyclia, Harting, 1863, Fauna Banda-Zee, p. 11, pl. i. fig. 19.

Trematodiscus heterocyclus, Stöhr, 1880, Palæontogr., vol. xxvi. p. 108.

All rings of the disk concentric, circular, connected by numerous radial beams, which are partly piercing, partly alternating. The breadth of the rings increases gradually from the centre towards the periphery, corresponding also to the size of the pores; two to three circular pores on the breadth of each ring.

Dimensions.—Diameter of the disk (with six rings) 0.17; breadth of the second ring 0.007, of the sixth 0.02; pores 0.002 to 0.006.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface; also fossil in Tertiary rocks of Barbados and the Mediterranean.

9. Porodiscus quadrigatus, n. sp. (Pl. , fig. 3).

All rings of the disk concentric, of nearly equal breadth, connected by four interradial beams, perpendicular one to another. The first ring (surrounding the central chamber) with eight chambers, the second only with four (alternating with the four radial beams). Size of the four chambers of each ring increases much towards the periphery. Pores regular, circular, about two on the breadth of each ring.

Dimensions.—Diameter of the disk (with six rings) 0.18; breadth of each ring 0.05; pores 0.004.

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

Subgenus 2. Perispira, Haeckel, 1881, Prodromus, p. 459.

Definition.—The inner rings of the disk concentric (commonly circular); the outer rings spirally convoluted.

10. Porodiscus perispira, n. sp. (Pl. , fig. 2).

Perispira perforata, Haeckel, 1881, Prodromus.

Inner rings of the disk (two or three) concentric, outer rings (three or four) spirally convoluted, spiral line simple. All rings nearly of the same breadth, connected by alternating irregular radial beams. Pores irregular, two to three on the breadth of each ring.

Dimensions.—Diameter of the disk (with six rings) 0.17; breadth of each ring 0.016; pores 0.003 to 0.005.

Habitat.—Pacific, central area, Stations 272 to 274, surface.

11. Porodiscus radiatus, n. sp.

Perispira radiata, Haeckel, 1881, Prodromus.

Inner rings of the disk (four or five) concentric, outer rings (three or four) spirally convoluted, spiral line simple. All rings connected by piercing radial beams (eight in the inner half, sixteen in the outer half). Breadth of the rings and of the pores increasing from the centre towards the periphery, three to four pores on the breadth of each ring.

Dimensions.—Diameter of the disk (with eight rings) 0.18; breadth of the second ring 0.006, of the eighth ring 0.02; pores 0.002 to 0.006.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Subgenus 3. Centrospira, Haeckel, 1881, Prodromus, p. 459.

Definition.—The inner rings of the disk spirally convoluted, the outer rings concentric (commonly circular).

12. Porodiscus centrospira, n. sp. (Pl. , fig. 6).

Centrospira perispongidium, Haeckel, 1881, Prodromus.

Inner rings of the disk (two or three) spirally convoluted (with simple or double spiral line), outer rings (three or four) concentric, subcircular. All rings nearly of the same breadth, connected by alternating radial beams. Pores subregular, two to three on the breadth of each ring. Lattice-work in the periphery of the disk a little spongy (as in Pl. , fig. 11).

Dimensions.—Diameter of the disk (with five rings) 0.15; breadth of each ring 0.015; pores 0.003.

Habitat.—Pacific, central area, Station 267, depth 2700 fathoms.

Subgenus 4. Discospira, Haeckel, 1862, Monogr. d. Radiol., p. 513.

Definition.—All rings of the disk spirally convoluted, forming parts of a simple or double spiral turning.

13. Porodiscus helicoides, Haeckel.

Discospira helicoides, Haeckel, 1862, Monogr. d. Radiol., p. 514, Taf. xxix. fig. 7.

Trematodiscus helicoides, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 841.

All rings of the disk spirally convoluted around the central chamber; spiral line regular, simple. All rings nearly of the same breadth, connected by numerous alternating radial beams. Chambers little different in size, little longer than broad. Pores of equal size, regular, two on the breadth of each ring.

Dimensions.—Diameter of the disk (with ten rings) 0.2; breadth of each ring 0.01; pores 0.0025.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific; also fossil in the Tertiary rocks of the Mediterranean, Sicily, Oran, &c.

14. Porodiscus spiralis, Haeckel.

Flustrella spiralis, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 210; Mikrogeol., 1854, Taf. xix. fig. 62.

Discospira spiralis, Haeckel, 1862, Monogr. d. Radiol., p. 513.

All rings of the disk spirally convoluted around the central chamber; spiral line regular, simple. All rings nearly of the same breadth, connected by numerous (twelve to sixteen) piercing radial beams. Chambers increasing in size from the centre towards the periphery. Pores irregular, of different size, one and a half to two on the breadth of each ring.

Dimensions.—Diameter of the disk (with eight rings) 0.16; breadth of each ring 0.01; pores 0.004.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; also fossil in the Tertiary rocks of Barbados, Sicily, Greece, &c.

15. Porodiscus operculina, Haeckel.

Discospira operculina, Haeckel, 1862, Monogr. d. Radiol., p. 514, Taf. xxix. fig. 8.

All rings of the disk spirally convoluted around the central chamber, spiral line regular, simple. Breadth of the rings and length of the chambers increasing in size from the centre towards the periphery. Most part of chambers twice as long as broad. Pores irregular, of very different sizes, two to three on the breadth of each ring.

Dimensions.—Diameter of the disk (with six rings) 0.16; breadth of the rings 0.012 to 0.016; pores 0.002 to 0.006.

Habitat.—Mediterranean (Messina), surface.

16. Porodiscus bilix, Haeckel.

Discospira bilix, Stöhr, 1880, Palæontogr., vol. xxvi. p. 113, Taf. vi. fig. 3.

All rings of the disk spirally convoluted around the large elliptical central chamber. Spiral convolutions of the inner rings simple, of the outer rings double; the latter twice as broad as the former. Pores regular, circular, in the inner rings one pore on the breadth, in the outer rings two to three pores. Radial beams piercing, numerous, on the margin prominent.

Dimensions.—Diameter of the disk (with six rings) 0.14; breadth of the inner rings 0.007, of the outer 0.013; pores 0.0017.

Habitat.—Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.

17. Porodiscus bispiralis, Haeckel.

Stylodictya bispiralis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 160. Taf. xxiv. fig. 1.

All rings of the disk spirally convoluted, in a perfect double spiral, with increasing breadth of the rings; the fourth ring twice as broad as the first. Pores regular, circular; in the inner rings one pore on the breadth, in the outer rings two to three pores. Radial beams piercing, numerous, prominent on the margin.

Dimensions.—Diameter of the disk (with four rings) 0.1; breadth of the inner rings 0.006, of the outer 0.012; pores 0.0015.

Habitat.—Fossil in the rocks of Barbados; living in the depths of the Central Pacific, Station 268, depth 2900 fathoms.

18. Porodiscus duplex, Haeckel.

Discospira duplex, Stöhr, 1880, Palæontogr., vol. xxvi. p. 114, Taf. vi. fig. 4.

All rings of the disk spirally convoluted, in a perfect double spiral, with increasing breadth of the broad rings. Pores regular, circular; in the inner rings two to three, in the outer four to five on the breadth. Radial beams interrupted. Margin of the rings thorny.

Dimensions.—Diameter of the disk (with three rings) 0.15; breadth of the rings 0.02 to 0.04; pores 0.007.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

19. Porodiscus semispiralis, n. sp. (Pl. , fig. 4).

All rings of the disk spirally convoluted, divided by four radial, perpendicularly crossed and zigzag shaped beams into four quadrants; the quarter rings of each quadrant halving the rings of each adjacent quarter. Half spiral line often irregular or partly interrupted. Breadth of all rings nearly equal. Pores irregular, roundish, two on the breadth of each ring. Margin of the disk dentated.

Dimensions.—Diameter of the disk (with nine rings) 0.22; breadth of each ring 0.012; pores 0.002 to 0.006.

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

Subgenus 5. Atactodiscus, Haeckel, 1881, Prodromus, p. 459.

Definition.—Rings of the disk more or less irregular, partly concentric, partly spirally convoluted, often interrupted.

20. Porodiscus deformis, Haeckel.

Discospira deformis, Stöhr, 1880, Palæontogr., vol. xxvi. p. 114, Taf. vi. fig. 6.

Rings of the disk irregular, partly concentric, partly spiral, often interrupted, increasing in breadth from the centre. Radial beams not piercing; pores regular, circular, two to six on the breadth of the different rings. (Very variable and irregular, sometimes more spiral, at other times more concentric, but always with equal pores.)

Dimensions.—Diameter of the disk (with four rings) 0.18; breadth of the first ring 0.014, of the second 0.03, of the fourth 0.06; pores 0.005.

Habitat.—Fossil in the Tertiary rocks of Barbados and Sicily; living in the Central Pacific, Stations 266 to 268, depths 2700 to 2900 fathoms.

21. Porodiscus irregularis, n. sp. (Pl. , fig. 7).

Atactodiscus irregularis, Haeckel, 1881, Prodromus, p. 459.

Perispongidium irregulare, Haeckel, 1878, MS. et Atlas (pl. xli. fig. 7).

Rings of the disk irregular, partly concentric, partly spiral, often interrupted, with nearly equal breadth. Radial beams not piercing; pores irregular, roundish, two to four on the breadth of each ring; network in the periphery of the disk spongy. (Very variable and irregular, sometimes more spiral, at other times more concentric; disk in the peripheral part often more or less spongy. Differs from the preceding by the equal breadth of the rings and the different size of the pores.)

Dimensions.—Diameter of the disk (with six rings) 0.15; breadth of each ring 0.011; pores 0.002 to 0.004.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface; also fossil in Barbados.

Genus 215. Perichlamydium, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Porodiscida with a simple circular disk (without radial spines and chambered arms), surrounded on the margin by a thin porous (but not chambered) equatorial girdle.

The genus Perichlamydium differs from Porodiscus only in the development of a thin, porous, equatorial girdle, which surrounds the circular margin of the chambered disk. This girdle lies in the equatorial plane of the lenticular disk, and represents a very delicate siliceous plate, perforated by numerous small pores. Sometimes the proximal part of the girdle is ribbed by thin radial beams, the distal prolongations of the radial rods of the central disk. If these ribs reach the margin of the girdle and are prominent over it, Perichlamydium passes over into Stylochlamydium.

1. Perichlamydium praetextum, Ehrenberg.

Perichlamydium praetextum, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 21 (non 20).

Perichlamydium praetextum, Haeckel, 1862, Monogr. d. Radiol., p. 495.

All rings of the disk (three to four) concentric, circular, of equal breadth, with interrupted (not piercing) radial beams. Equatorial girdle without radial beams, nearly as broad as the disk; its circular pores of the same size as those of the disk; about two pores on the breadth of each ring.

Dimensions.—Diameter of the disk (without the girdle, with four rings) 0.11; breadth of each ring 0.012; breadth of the girdle 0.06 to 0.1; pores 0.004.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, surface; also fossil in the Tertiary rocks of Barbados and Sicily.

2. Perichlamydium saturnus, n. sp. (Pl. , fig. 5).

All rings of the disk (three to four) concentric, circular (sometimes partly concentric, circular, partly spiral, or irregular), with interrupted (not piercing) radial beams. Equatorial girdle without radial beams, about half as broad as the disk; its circular pores very small, scarcely half as large as those of the disk; about three pores on the breadth of each ring. (Very variable in the ring-form, differs from the preceding in the small pores of the girdle.)

Dimensions.—Diameter of the disk (without the girdle, with three rings) 0.11; breadth of each ring 0.02, pores 0.004, breadth of the girdle 0.05, pores 0.002.

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

3. Perichlamydium accrescens, Haeckel.

Discospira accrescens, Stöhr, 1880, Palæontogr., vol. xxvi. p. 114, Taf. vi. fig. 5.

All rings of the disk (six to seven) not concentric, convoluted in a simple spiral, of nearly equal breadth, with interrupted (not piercing) radial beams. Equatorial girdle in the proximal part with numerous radial beams, which do not reach its margin; its pores half as large as those of the disk, where one to two pores arise on the breadth of each ring. (The girdle becomes twice to three times as broad as in the figure of Stöhr.)

Dimensions.—Diameter of the disk (with seven rings, without the girdle) 0.13; breadth of each ring 0.007 to 0.01; pores 0.0036; breadth of the girdle 0.05, pores of it 0.0017.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte (Stöhr), Caltanisetta (Haeckel); living in the Central Pacific, Station 266, depth 2750 fathoms.

4. Perichlamydium spirale, Ehrenberg.

Perichlamydium spirale, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. xxii. fig. 12.

All rings of the disk (three to four) not concentric, convoluted in a simple spiral, of increasing breadth from the centre; connected by numerous piercing radial beams. Equatorial girdle about half as broad as the disk, without radial beams; its pores of the same size as those of the disk, regular, circular; three pores on the breadth of the first ring, six pores of the fourth ring.

Dimensions.—Diameter of the disk (with four rings, without the girdle) 0.12; breadth of the first ring 0.01, of the fourth 0.02; breadth of the girdle 0.05; pores 0.003.

Habitat.—Fossil in the rocks of Barbados.