Subfamily 2. Diplozonaria, Haeckel
Definition.—Pylonida with two concentric systems of fenestrated girdles, lying in two concentric lentelliptical faces (every one system with one to three girdles, lying in one lentelliptical face).
Genus 282. Amphipyle, Haeckel, 1881, Prodromus, p. 463.
Definition.—Pylonida with trizonal lentelliptical medullary shell, surrounded by one single (transverse) latticed cortical girdle.
The genus Amphipyle opens the large series of Diplozonaria, comprising all Pylonida, the shell of which is composed of two concentric systems of latticed girdles; the first system constituting the characteristic "trizonal medullary shell" or "Larnacilla-shell;" the second system composed of one to three girdles of the second order. The first system lies inside, the second outside the central capsule. In Amphipyle only the first (transverse) girdle of the second system becomes developed, and therefore on both poles of the principal axis are two large open gates. Amphipyle repeats the two-winged form of Monozonium; but whilst the medullary shell in this latter is a simple central chamber, it is here a trizonal Larnacilla-shell.
Subgenus 1. Amphipylissa, Haeckel.
Definition.—Cortical shell smooth or thorny, but without large, symmetrically disposed spines.
1. Amphipyle aceros, n. sp.
Cortical shell quite smooth, without any spines or thorns. Both lateral wings (or opposite half girdles) semilunar, with convex lateral crest, three times as long as broad; twice as broad as the trizonal lentelliptical medullary shell.
Dimensions.—Length of the medullary shell 0.05, breadth 0.03; length of each lateral wing (or principal dimension of the latticed girdle) 0.18, breadth of it (or transverse dimension of each girdle-tube) 0.06.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
2. Amphipyle stenoptera, n. sp.
Cortical shell smooth, without spines. Both lateral wings of the same breadth as the lentelliptical medullary shell, but five times as long as broad, prolonged on both ends into cylindrical latticed tubes, with rectilinear lateral crest.
Dimensions.—Length of the medullary shell 0.06, breadth 0.04; length of each cylindrical lateral wing 0.2, breadth 0.04.
Habitat.—South Atlantic, off Ascension Island, Station 343, surface.
3. Amphipyle platyptera, n. sp.
Cortical shell thorny, but without larger spines. Both lateral wings nearly triangular, very broad and short, four times as broad as the medullary shell between them, and only twice as long as broad, with rectilinear lateral crest.
Dimensions.—Length of the medullary shell 0.05, breadth 0.25; length of each lateral wing 0.18, breadth 0.09.
Habitat.—Indian Ocean, Ceylon, Haeckel, surface.
Subgenus 2. Amphipylura, Haeckel.
Definition.—Cortical shell armed with large, symmetrically disposed spines.
4. Amphipyle amphiceros, n. sp.
Cortical shell with two conical spines on the poles of the longitudinal axis (of the lentelliptical medullary shell), without other large spines, but with small thorns on the surface; two to three longitudinal rows of irregular, roundish pores on each half wing of the cortical girdle.
Dimensions.—Length of the medullary shell (or principal axis) 0.06, breadth (or transverse axis) 0.04; length of each lateral wing 0.2, breadth of it 0.05.
Habitat.—Western Tropical Pacific, Station 222, surface.
5. Amphipyle tetraceros, n. sp. (Pl. , fig. 5).
Cortical shell with smooth surface, and with four strong conical spines in the lateral plane, opposite in pairs on the ends of the concave lateral crests (one pair on the end-points of the lateral line of each wing); four to five longitudinal rows of irregular, roundish pores on each half wing of the cortical girdle. Surface of the medullary shell spiny.
Dimensions.—Length of the medullary shell 0.08, breadth of the same 0.05; length of each lateral wing 0.16, breadth 0.04.
Habitat.—Pacific, central area, Station 271, surface.
6. Amphipyle stauroceros, n. sp.
Cortical shell with four strong conical spines, two on the poles of the longitudinal axis, two opposite on the poles of the transverse axis (perpendicular to the former). Three to four longitudinal rows of irregular, roundish pores on each half wing of the cortical girdle, about six pores in the longest row. Lateral crest convex.
Dimensions.—Length of the medullary shell 0.05, breadth 0.03; length of each lateral wing 0.15, breadth 0.08.
Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.
7. Amphipyle amphiptera, n. sp. (Pl. , fig. 7).
Cortical shell with six strong conical spines, lying in the lateral plane in three parallel longitudinal lines; two on the poles of the longitudinal axis, two others on the poles of the wing axes, which are parallel to the former. Two to three longitudinal rows of irregular, roundish pores on each half wing of the cortical girdle, about eight pores in the longest row. Lateral crest convex, thorny.
Dimensions.—Length of the medullary shell 0.06, breadth 0.045; length of each lateral wing 0.09, breadth 0.035.
Habitat.—Western Tropical Pacific, Station 224, surface.
8. Amphipyle hexaceros, n. sp.
Cortical shell thorny, with six strong conical spines lying in the lateral plane; two on the poles of the lateral axis (in the central point of each wing), two on the end-points of the triangular crest of each wing (on both poles of the longitudinal wing-axis).
Dimensions.—Length of the medullary shell 0.06, breadth 0.04; length of each lateral wing 0.13, breadth 0.07.
Habitat.—South Pacific, Station 291, surface.
9. Amphipyle octoceros, n. sp.
Cortical shell thorny, with eight long radial spines, lying in two crossed diagonal planes, opposite in pairs. These eight horns are the prolongations of the anterior and posterior edges of each wing, on both sides of its lateral plane; they are of great importance, as appearing (by heredity) in many other Pylonida (e.g., in Tetrapyle octacantha). Lateral crest of each wing without spines, slightly convex.
Dimensions.—Length of the medullary shell 0.07, breadth 0.05; length of each lateral wing 0.15, breadth 0.06.
Habitat.—Pacific, central area, Stations 270 to 274, surface.
10. Amphipyle cladoceros, n. sp.
Cortical shell spiny, with eight strong ramified radial spines, lying in the same two crossed diagonal planes as in the preceding species. It differs from this in the ramification of the eight horns, which bear six to nine irregular lateral branches, partly simple, partly bifurcate. Lateral crest of each wing spiny, convex.
Dimensions.—Length of the medullary shell 0.06, breadth 0.045; length of each lateral wing (without spines) 0.2, breadth 0.09.
Habitat.—Indian Ocean, surface, Madagascar, Rabbe.
11. Amphipyle decaceros, n. sp.
Cortical shell spiny, with ten strong conical spines; eight lying in two crossed diagonal planes, in the same disposition (opposite in pairs) as in both preceding species; two others opposite on the poles of the principal axis, arising from both poles of the medullary shell (columella-beams). Spiny crest of the wings convex, semilunar.
Dimensions.—Length of the medullary shell 0.04, breadth 0.03; length of each lateral wing 0.12, breadth 0.04.
Habitat.—North Atlantic, Station 354, surface.
12. Amphipyle dodecaceros, n. sp.
Cortical shell thorny, with twelve large cylindrical spines; eight lying in two crossed diagonal planes, in the same disposition (opposite in pairs) as in the three preceding species; four others crossed at right angles in the lateral plane, two opposite on the poles of the principal, two on the poles of the lateral axis (the latter shorter). Both lateral wings nearly rhombic.
Dimensions.—Length of the medullary shell 0.06, breadth 0.04; length of the lateral wings 0.15, breadth 0.05.
Habitat.—South Atlantic, coast of Brazil, Rabbe, surface.
13. Amphipyle callizona, n. sp. (Pl. , fig. 6).
Cortical shell smooth, with sixteen strong and short conical spines, lying opposite in pairs in two crossed diagonal planes; each lateral wing four-sided prismatic, its lateral face concave, both ends truncated, and each end provided with four divergent spines. Length of the wings somewhat greater, but breadth smaller, than that of the medullary shell.
Dimensions.—Length of the medullary shell 0.07, breadth 0.05; length of the lateral wings 0.09, breadth 0.03.
Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.
Genus 283. Tetrapyle, J. Müller, 1858, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 154.
Definition.—Pylonida with trizonal lentelliptical medullary shell, surrounded by two crossed latticed cortical girdles, one smaller (primary) transverse, and one larger (secondary) lateral girdle. Four gates between the two cortical girdles simple, without a sagittal septum.
The genus Tetrapyle, till 1881 the only known genus of the whole family, was founded by Johannes Müller in 1858, and clearly illustrated by the Mediterranean (and common cosmopolitan) Tetrapyle octacantha, hitherto the best known type of this family. Afterwards (1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 832) Ehrenberg founded the genus Schizomma for a nearly allied form, which exhibits only slight specific differences (compare my Monograph, 1862, p. 434). Some good remarks on the structure of this typical genus and its relations to other Pylonida are to be found in Richard Hertwig's Organismus, &c., 1879, p. 52, but the true trizonal structure of the medullary shell in this genus was not recognised by him, so that his description agrees more with Dizonium. We confine here the genus Tetrapyle to those Pylonida for which Tetrapyle octacantha of J. Müller remains the determining type; the cortical shell is composed only of two perfect lattice-girdles (the transverse and lateral), between which four wide gates remain open. This structure is similar to that of Dizonium; but whilst here the medullary shell is a simple central chamber, in Tetrapyle it is a complete trizonal or Larnacilla-shell.
Subgenus 1. Tetrapylissa, Haeckel.
Definition.—Cortical shell smooth or thorny, but without large, symmetrically disposed spines.
1. Tetrapyle circularis, n. sp. (Pl. , fig. 8).
Cortical shell rough, without radial spines. Lateral girdle circular, therefore the longitudinal axis is equal to the transverse. Four gates kidney-shaped, twice as broad as high. In each half wing of the transverse girdle six to seven longitudinal rows of irregular, roundish pores.
Dimensions.—Medullary shell 0.05 long, 0.04 broad; cortical shell 0.15 long and broad; gates 0.04 high, 0.08 broad.
Habitat.—Pacific, central area, Station 263, surface.
2. Tetrapyle circopyle, n. sp.
Cortical shell smooth, without radial spines. Lateral girdle elliptical, one and a half times as long as broad. Four gates nearly circular. On each half wing of the transverse girdle four to five rows of subregular, circular pores. (Similar to Tetrapyle pleuracantha, Pl. , fig. 9, but without lateral spines.)
Dimensions.—Medullary shell 0.04 long, 0.03 broad; cortical shell 0.16 long, 0.11 broad; gates 0.05 high and broad.
Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.
3. Tetrapyle quadriloba, Haeckel.
Tetrapyle quadriloba, Haeckel, 1862, Monogr. d. Radiol., p. 436.
Schizomma quadrilobum, Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 815; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. x. figs. 12-14.
Cortical shell thorny, without regular, radial spines. Lateral girdle elliptical, one and a half times as long as broad. Four gates nearly circular. On each half wing of the transverse girdle three to four rows of irregular, roundish pores.
Dimensions.—Medullary shell 0.06 long, 0.04 broad; cortical shell 0.16 long, 0.1 broad; diameter of the gates 0.05.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian Ocean, Pacific, surface.
4. Tetrapyle nephropyle, n. sp.
Cortical shell thorny, without radial spines. Lateral girdle elliptical, one and a third times as long as broad. Four gates kidney-shaped, nearly twice as broad as high, with two prominent polar spines on the poles of the longitudinal axis of the medullary shell. On each half wing of the transverse girdle three to four longitudinal rows of large roundish pores.
Dimensions.—Medullary shell 0.06 long, 0.04 broad; cortical shell 0.24 long, 0.18 broad; gates 0.05 high, 0.08 broad.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
5. Tetrapyle cardiopyle, n. sp.
Cortical shell rough, without radial spines. Lateral girdle with hexagonal contour, nearly cylindrical in the middle part, conical at both ends, twice as long as broad. Four gates heart-shaped, about as high as broad. On each half wing of the transverse girdle three to four longitudinal rows of subregular, polygonal pores.
Dimensions.—Medullary shell 0.04 long, 0.02 broad; cortical shell 0.14 long, 0.07 broad; gates 0.05 high and broad.
Habitat.—Eastern Tropical Atlantic, Station 348, depth (2450) fathoms.
Subgenus 2. Tetrapylura, Haeckel.
Definition.—Cortical shell armed with large, symmetrically disposed spines.
6. Tetrapyle fusiformis, n. sp.
Cortical shell rough, with two strong conical spines on the poles of the longitudinal axis. Lateral girdle spindle-shaped, one and a half times as long as broad. Four gates kidney-shaped, twice as broad as high. On each half wing of the transverse girdle four to five longitudinal rows of irregular, roundish pores.
Dimensions.—Medullary shell 0.07 long, 0.05 broad; cortical shell 0.18 long, 0.12 broad; gates 0.04 high, 0.08 broad.
Habitat.—Western Tropical Atlantic, Mexican Gulf Stream, depth 1500 fathoms, Schaffner.
7. Tetrapyle pleuracantha, n. sp. (Pl. , fig. 9).
Cortical shell rough, with two strong conical spines on the poles of the transverse axis. Lateral girdle elliptical, one and half times as long as broad. Four gates subcircular or nearly hexagonal, about as high as broad. On each half wing of the transverse girdle three to four longitudinal rows of very irregular pores.
Dimensions.—Medullary shell 0.045 long, 0.035 broad; cortical shell 0.16 long, 0.11 broad; gates 0.045 high and broad.
Habitat.—Western Tropical Pacific, off New Guinea, Stations 222 to 224, depths 1850 to 2450 fathoms.
8. Tetrapyle transversa, n. sp.
Cortical shell thorny, with two strong conical lateral spines on the poles of the transverse axis. Lateral girdle elliptical, only four-fifths as long as broad. Four gates elliptical, twice as broad as high, with two prominent spines on the poles of the longitudinal axis of the medullary shell. On each half wing of the transverse girdle five to six longitudinal rows of subregular, roundish pores. (Similar to Octopyle transversa, but without sagittal septum and with stronger lateral spines.)
Dimensions.—Medullary shell 0.05 long, 0.035 broad; cortical shell 0.12 long, 0.15 broad; gates 0.03 high, 0.06 broad.
Habitat.—Southern Pacific, Station 290, surface.
9. Tetrapyle cruciata, n. sp.
Cortical shell smooth, with four strong radial spines, two on the poles of the longitudinal axis, two on the poles of the transverse axis. Lateral girdle nearly circular, quite as long as broad. Four gates kidney-shaped, twice as broad as high. On each half wing of the transverse girdle five to six rows of subregular, circular pores.
Dimensions.—Medullary shell 0.06 long, 0.05 broad; cortical shell 0.16 long and broad; gates 0.05 high, 0.09 broad.
Habitat.—South Atlantic, Station 330, surface.
10. Tetrapyle staurophora, n. sp.
Cortical shell thorny, with four strong radial spines, two on the poles of the longitudinal axis, two on the poles of the transverse axis. Lateral girdle elliptical, one and a half times as long as broad. Four gates nearly hexagonal, quite as high as broad. On each half wing of the transverse girdle three to four longitudinal rows of irregular, roundish pores.
Dimensions.—Medullary shell 0.06 long, 0.04 broad; cortical shell 0.18 long, 0.12 broad; gates 0.08 high and broad.
Habitat.—Western Tropical Atlantic, coast of Brazil, Rabbe, surface.
11. Tetrapyle quadricornis, n. sp.
Cortical shell thorny, with four strong horn-like curved spines, lying in the lateral plane and converging in pairs towards the poles of the transverse axis. Lateral girdle elliptical, one and a third times as long as broad. Four gates kidney-shaped, twice as broad as high. On each half wing of the transverse girdle four to five rows of irregular, roundish pores. (May be only the young form of Pylonium quadricorne, Pl. , fig. 14.)
Dimensions.—Medullary shell 0.05 long, 0.04 broad; cortical shell 0.16 long, 0.12 broad; gates 0.03 high, 0.07 broad.
Habitat.—Pacific, central area, Stations 270 to 274, surface.
12. Tetrapyle tetracantha, n. sp.
Cortical shell thorny, with four strong radial spines lying in the lateral plane and in pairs in its two crossed diagonal axes. Lateral girdle elliptical, constricted in the middle, nearly twice as long as broad. Four gates kidney-shaped, one and a half times as broad as high. On each half wing of the transverse girdle three to four longitudinal rows of large, irregular, roundish pores. (Similar to Tetrapylonium quadrangulare, Pl. , fig. 15, but without a sagittal girdle and with stronger lateral spines.)
Dimensions.—Medullary shell 0.06 long, 0.04 broad; cortical shell 0.18 long, 0.1 broad; gates 0.007 high, 0.01 broad.
Habitat.—North Atlantic, Canary Islands, Station 353, surface.
13. Tetrapyle quadrigata, n. sp.
Cortical shell thorny, with four brush-like groups of radial spines on the four diagonal corners of the lateral plane, opposite in pairs in diagonal axes. Lateral girdle nearly square, somewhat broader than long. Four gates kidney-shaped, twice as broad as high. On each half wing of the transverse girdle five to six longitudinal rows of irregular, roundish pores.
Dimensions.—Medullary shell 0.06 long, 0.04 broad; cortical shell 0.14 long, 0.15 broad; gates 0.03 high, 0.07 broad.
Habitat.—Pacific, central area, Station 270, surface.
14. Tetrapyle octacantha, J. Müller.
Tetrapyle octacantha, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 33, Taf. ii. figs. 1-6.
Tetrapyle octacantha, Haeckel, 1862, Monogr. d. Radiol., p. 435.
Tetrapyle octacantha, R. Hertwig, 1879, Organismus d. Radiol., p. 52, Taf. iv. fig. 7, Taf. vi. figs. 2, 5, 5a.
Cortical shell thorny, with eight long and thin, cylindrical radial spines, lying in two crossed diagonal planes, opposite in pairs. These eight characteristic diagonal spines (or "angular spines") are the same as in Amphipyle octoceros and many other Pylonida, and arise as prolongations of the proximal edges of the four gates (or of the lateral wings on the eight points, where they are intersected by the edges of the lateral ring). This cosmopolitan, widely distributed and very variable species was a long time the only known species of all the Pylonida, and very accurately first described (1858) by Johannes Müller, afterwards (1879) by R. Hertwig. But in the descriptions of these authors also some different species (such as the following) may be confounded with the true typical Tetrapyle octacantha. The four gates of this species are transverse-elliptical or almost triangular, nearly twice as broad as high.
Dimensions.—Length of the medullary shell 0.04, breadth 0.03; length of the cortical shell 0.18, breadth 0.13; height of the gates 0.05, breadth 0.08.
Habitat.—Cosmopolitan; very common in all warmer seas, Mediterranean, Atlantic, Indian, Pacific, surface.
15. Tetrapyle cladacantha, n. sp.
Cortical shell thorny, with eight strong ramified radial spines, lying opposite in pairs in two crossed diagonal planes, as in the preceding species. It differs from this by the peculiar ramification of the eight spines, which bear two to eight simple or furcate lateral branches arising under right angles (already commencing in a transitional variety of Tetrapyle octacantha, J. Müller, loc. cit., Taf. ii. figs. 5, 6). Four gates transverse-elliptical, one and a half times as broad as high.
Dimensions.—Medullary shell 0.05 long, 0.04 broad; cortical shell 0.16 long, 0.13 broad; gates 0.05 high, 0.08 broad.
Habitat.—Mediterranean (Corfu), Haeckel, surface.
16. Tetrapyle pluteus, Haeckel.
Tetrapyle octacantha, var., J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. iii. figs. 7-12.
Cortical shell thorny, with eight strong radial spines, lying opposite in pairs, as in the two foregoing species. On the distal edge each of the four triangular gates is protected by a prominent roof of lattice-work (or "pluteus"), which arises from the distal part of the lateral girdle and connects the two angular diagonal spines of each gate. Therefore the shell assumes the characteristic form very well represented by J. Müller in his fig. 11 (seen from the lateral side) and fig. 7 (seen from the pole of the principal axis).
Dimensions.—Medullary shell 0.04 long, 0.03 broad; cortical shell 0.15 long, 0.11 broad; gates 0.045 high, 0.07 broad.
Habitat.—Mediterranean, Atlantic, Stations 348 to 353, &c., surface.
17. Tetrapyle turrita, n. sp. (Pl. , fig. 10).
Cortical shell smooth, but with ten strong conical spines, two on the poles of the principal axis, eight others symmetrically distributed on both sides of the distal edge of the four roundish gates, and directed towards the transverse axis. Lateral girdle lanceolate, twice as long as broad.
Dimensions.—Medullary shell 0.05 long, 0.04 broad; cortical shell 0.2 long, 0.1 broad; gates 0.05 high, 0.07 broad.
Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.
18. Tetrapyle dodecaceros, n. sp.
Cortical shell thorny, with twelve stronger conical spines, eight diagonal spines in two crossed planes (as in Tetrapyle octacantha), and four others in the lateral plane, in pairs on both sides of a deep sagittal constriction of the quadrangular lateral girdle. Four gates kidney-shaped, twice as broad as high. On each half wing of the transverse girdle five to six longitudinal rows of irregular, roundish pores.
Dimensions.—Medullary shell 0.06 long, 0.04 broad; cortical shell 0.18 long, 0.14 broad; gates 0.04 high, 0.08 broad.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
Genus 284. Octopyle, Haeckel, 1881, Prodromus, p. 464.
Definition.—Pylonida with trizonal lentelliptical medullary shell, surrounded by two crossed, latticed, cortical girdles; one smaller (primary) transverse, and one larger (secondary) lateral girdle. Four gates between the two cortical girdles divided by a sagittal septum into eight gates.
The genus Octopyle comprises those Pylonida which are distinguished from the nearly allied Tetrapyle by the development of a sagittal septum, dividing the four gates of the latter into eight separate gates. The septum begins with the formation of two axial rods or columellæ, which afterwards become branched; the branches communicating one with another and with the middle parts of the lateral girdle (on the poles of the principal axis), there is formed a latticed septum in the sagittal plane, which separates more or less incompletely the right and left halves of the shell. The four gates of Tetrapyle become halved by this septum, and their number doubled.
Subgenus 1. Octopylissa, Haeckel.
Definition.—Cortical shell smooth or thorny, but without larger symmetrically disposed spines.
1. Octopyle ovulina, n. sp.
Cortical shell lentelliptical, smooth, without thorns. Lateral girdle elliptical, one and a third times as long as broad. Transverse girdle narrow, with two pores on the isthmus (or on the narrowest part of each quadrant). Sagittal septum as long as the elliptical medullary shell. Eight gates egg-shaped.
Dimensions.—Length of the medullary shell 0.05, breadth 0.035; length of the cortical shell 0.16, breadth 0.12.
Habitat.—Pacific, central area, Station 274, surface.
2. Octopyle quadrata, n. sp.
Cortical shell thorny, nearly square, of equal length and breadth. Lateral girdle quadrangular, with rounded edges, of equal length and breadth. Transverse girdle narrow, with three pores on the isthmus. Sagittal septum of the same length as the subspherical medullary shell. Eight gates nearly circular.
Dimensions.—Diameter of the medullary shell 0.04, of the cortical shell 0.14.
Habitat.—Northern Pacific, Station 244, depth 2900 fathoms.
3. Octopyle subglobosa, n. sp.
Cortical shell nearly spherical, thorny, of equal length and breadth. Lateral girdle broad, nearly circular. Transverse girdle broad, with four pores on the isthmus. Sagittal septum shorter than the subspherical medullary shell. Eight gates egg-shaped.
Dimensions.—Diameter of the medullary shell 0.05, of the cortical shell 0.13.
Habitat.—Southern Pacific, Station 300, depth 1375 fathoms.
4. Octopyle transversaria, n. sp.
Cortical shell thorny, transverse-elliptical. Lateral girdle very broad, one and a third times as broad as long. Transverse girdle also very broad, with five pores on the isthmus. Sagittal septum shorter than the elliptical medullary shell. Eight gates small, roundish.
Dimensions.—Length of the medullary shell 0.05, breadth 0.04; length of the cortical shell 0.11, breadth 0.15.
Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.
Subgenus 2. Octopylura, Haeckel.
Definition.—Cortical shell armed with large, symmetrically disposed spines.
5. Octopyle amphistyle, n. sp.
Cortical shell smooth, nearly spindle-shaped, about twice as long as broad. Transverse girdle broad, with four large pores on the isthmus. Lateral girdle lanceolate. Sagittal septa about as long as the medullary shell, prolonged at both poles of the principal axis into two opposite, strong, angular spines. Eight gates obliquely quadrangular.
Dimensions.—Length of the medullary shell 0.07, breadth 0.05; length of the cortical shell 0.2, breadth 0.12.
Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.
6. Octopyle staurostyle, n. sp.
Cortical shell nearly rhombic, smooth, one and a half times as long as broad, with four strong, conical, radial spines, two on the poles of the principal axis (as prolongations of the sagittal septa), two others on the poles of the transverse axis. Transverse girdle narrow, with two pores on the isthmus. Sagittal septa longer than the medullary shell. Eight gates triangular.
Dimensions.—Length of the medullary shell 0.04, breadth 0.03; length of the cortical shell 0.18, breadth 0.12.
Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.
7. Octopyle tetrastyle, n. sp.
Cortical shell lentelliptical, with rough surface and four angular radial spines in the lateral plane, opposite in pairs in two crossed diagonals. Lateral girdle nearly rectangular (each angle with one spine), one and a third times as long as broad. Sagittal septum longer than the hexagonal medullary shell. Eight gates egg-shaped.
Dimensions.—Length of the medullary shell 0.05, breadth 0.03; length of the cortical shell 0.16, breadth 0.12.
Habitat.—North Atlantic, Station 354, surface.
8. Octopyle tetraptera, n. sp.
Cortical shell quadrangular, with thorny surface and four latticed wing-like prolongations on the corners of the quadrangle, opposite in pairs in two crossed diagonals, each wing supported by a strong radial spine. Lateral girdle quadrangular, one and a half times as long as broad. On the isthmus of the transverse girdle four pores. Sagittal septum longer than the hexagonal medullary shell. Eight gates triangular.
Dimensions.—Length of the medullary shell 0.07, breadth 0.04; length of the cortical shell 0.24, breadth 0.16.
Habitat.—Pacific, central area, Station 271, surface.
9. Octopyle stenozona, n. sp. (Pl. , fig. 11).
Cortical shell quadrangular, with thorny surface, and four conical spines in the lateral plane, on the points, where both cortical girdles are crossed. Lateral girdle very narrow, nearly square, with rounded corners, of equal length and breadth. On the isthmus of the narrow transverse girdle only one pore. Sagittal septum of the same length as the subspherical medullary shell. Eight gates irregular roundish or nearly circular.
Dimensions.—Diameter of the medullary shell 0.04, of the cortical shell 0.14.
Habitat.—Tropical Atlantic, Station 338, depth 1990 fathoms.
10. Octopyle euryzona, n. sp.
Cortical shell nearly quadrangular, very thorny, with four bunches of stronger radial spines on the four corners. Lateral girdle broad, with rounded edges of the quadrangle, little longer than broad. On the isthmus of the broad transverse girdle four pores. Sagittal septum of the same length as the elliptical medullary shell, with many radial beams. Eight gates nearly square.
Dimensions.—Length of the medullary shell 0.05, breadth 0.035; length of the cortical shell 0.16, breadth 0.14.
Habitat.—Southern Atlantic, Station 332, depth 2200 fathoms.
11. Octopyle hexastyle, n. sp.
Cortical shell nearly rectangular, thorny, with six strong radial spines in the lateral plane, two opposite on the poles of the principal axis (prolongations of the principal beam at the sagittal septum), four others on the truncate corners of the quadrangular lateral girdle, which is one and a half times as long as broad. On the isthmus of the broad transverse girdle three pores. Sagittal septum longer than the hexagonal medullary shell. Eight egg-shaped gates.
Dimensions.—Length of the medullary shell 0.05, breadth 0.04; length of the cortical shell 0.18, breadth 0.12.
Habitat.—Northern Atlantic, surface; Canary Islands, Station 9, depth 3150 fathoms.
12. Octopyle sexangulata, n. sp. (Pl. , fig. 12).
Cortical shell thorny, hexagonal, with six strong conical radial spines on the six corners of the lateral girdle, lying in the lateral plane, two opposite on the poles of the transverse axis, four others in pairs on both sides of the annular sagittal constriction, which is only twice as long as the elliptical medullary shell. Transverse girdle broad, with five pores on the isthmus. Eight gates roundish, smaller than the medullary shell.
Dimensions.—Length of the medullary shell 0.045, breadth 0.035; length of the cortical shell 0.11, breadth 0.13.
Habitat.—Pacific, central area, Station 270, surface.
13. Octopyle octostyle, n. sp.
Cortical shell elliptical, thorny, with eight long cylindrical radial spines, lying in two crossed diagonal planes, opposite in pairs, quite as in the nearly related Tetrapyle octacantha. It differs from this species by the perfect, latticed, vertical sagittal septum, which divides every gate into two triangular halves. Lateral girdle elliptical, one and a third times as long as broad. Transverse girdle on the isthmus with three pores. Septum longer than the elliptical medullary shell.
Dimensions.—Length of the medullary shell 0.06, breadth 0.045; length of the cortical shell 0.16, breadth 0.12.
Habitat.—South Pacific, Station 288, surface.
14. Octopyle obtecta, n. sp.
Cortical shell quadrangular, thorny, with eight strong diagonal spines, lying in two crossed planes, and arising from the proximal edges of the gates in the same way as in the foregoing species. It differs from this by four prominent latticed roofs, which arise from the distal edge of the gates and connect the diagonal spines of one gate. Octopyle obtecta bears therefore the same relation to Octopyle octostyle that Tetrapyle pluteus does to Tetrapyle octacantha.
Dimensions.—Length of the medullary shell 0.055, breadth 0.04; length of the cortical shell 0.16, breadth 0.12.
Habitat.—Indian Ocean, surface, Madagascar, Rabbe.
15. Octopyle decastyle, n. sp. (Pl. , fig. 13).
Cortical shell thorny, nearly quadrangular, with ten stronger radial spines, two opposite on the poles of the principal axis (as prolongations of the axial beams), eight others opposite in pairs in two diagonal planes (as in the foregoing species). Lateral girdle nearly square, with slightly convex lateral faces, slightly concave principal faces. Transverse girdle broad, with four pores on the isthmus. Sagittal septum of the same length as the hexagonal medullary shell. Eight gates elliptical or irregular roundish.
Dimensions.—Length of the medullary shell 0.05, breadth 0.032; diameter of the cortical shell 0.15.
Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.
Genus 285. Pylonium, Haeckel, 1881, Prodromus, p. 464.
Definition.—Pylonida with trizonal lentelliptical medullary shell surrounded by three crossed latticed cortical girdles, one smaller (primary) transverse, one larger (secondary) lateral, and one (tertiary) sagittal girdle.
The genus Pylonium is the most highly developed among the Diplozonaria, with six complete latticed girdles, three on the medullary shell, three on the cortical shell, the latter corresponding to the former. In each of the two systems the transverse girdle is smaller than the lateral; the sagittal girdle may be smaller or larger than the lateral girdle. Pylonium repeats the typical form of Trizonium; but whilst in this latter the medullary centre of the shell is a simple spherical chamber, here in Pylonium it is a true trizonal or Larnacilla-shaped medullary shell.
Subgenus 1. Pylonissa, Haeckel.
Definition.—Cortical shell smooth or thorny, but without large, symmetrically disposed spines.
1. Pylonium circozonium, n. sp.
Cortical shell thorny, without radial spines; all its three girdles nearly of the same size, subcircular, very narrow, only with one to two rows of pores. Four gates subcircular.
Dimensions.—Principal axis 0.12, transverse axis 0.11; diameter of the subspherical medullary shell 0.05.
Habitat.—North Pacific, Station 244, depth 2900 fathoms.
2. Pylonium hexazonium, n. sp.
Cortical shell smooth, without symmetrical radial spines. Transverse girdle elliptical, one and a half times as long as broad. Lateral and sagittal girdles nearly circular. Four gates egg-shaped.
Dimensions.—Principal axis 0.16, transverse axis 0.15; diameter of the subspherical medullary shell 0.04.
Habitat.—South Pacific, Station 295, depth 1500 fathoms.
3. Pylonium nephropylium, n. sp.
Cortical shell thorny, without radial spines. All its three girdles elliptical, one and a third times as long as broad. Four gates kidney-shaped, nearly twice as broad as high.
Dimensions.—Principal axis 0.17, transverse axis 0.13; length of the lentelliptical medullary shell 0.04, breadth 0.03.
Habitat.—Pacific, central area, Station 273, depth 2350 fathoms.
Subgenus 2. Pylonura, Haeckel.
Definition.—Cortical shell armed with large, symmetrically disposed spines.
4. Pylonium quadricorne, n. sp. (Pl. , fig. 14).
Cortical shell thorny, with four strong horn-like curved spines in the lateral plane. All its three girdles elliptical, one and a third times as long as broad. Four gates kidney-shaped, twice as broad as high. (This species is a further developmental stage of Tetrapyle quadricornis, with perfect sagittal girdle.)
Dimensions.—Principal axis 0.16, transverse axis 0.12; length of the medullary shell 0.05, breadth 0.04.
Habitat.—Pacific, central area, Stations 270 to 274, surface; Indian Ocean, Madagascar, Rabbe, surface.
5. Pylonium octacanthum, n. sp.
Cortical shell thorny, with eight long and thin cylindrical radial spines, lying in two crossed diagonal planes, opposite in pairs, and arising from the eight points where the transverse girdle is crossed by the lateral girdle. All three girdles elliptical, one and a half times as long as broad; four gates triangular. (This species is a further developmental stage of Tetrapyle octacantha, with perfect sagittal girdle.)
Dimensions.—Principal axis 0.18, transverse axis 0.13; length of the medullary shell 0.03 to 0.04.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
6. Pylonium stenozonium, n. sp.
Cortical shell thorny, with eight short conical radial spines, lying in two crossed diagonal planes (as in the foregoing species). All three girdles nearly of the same size, subcircular, very narrow, only with one to two rows of pores. Four gates kidney-shaped.
Dimensions.—Principal axis 0.15, transverse axis 0.14; diameter of the quadrangular medullary shell 0.04.
Habitat.—Equatorial Atlantic, Station 347, surface.