Cortical shell thick walled, smooth, with subregular, circular, polygonally framed pores, quite as broad as the bars; ten to twelve on the half equator. Polar spines three-sided pyramidal, about as long as the half main axis, three times as broad at the base as the pores. (Much resembles Amphisphæra neptunus, p. 142, but differs from it by the prolongation of the main axis, which equals one and a half or one and a fourth the equatorial axis, and by the somewhat irregular formation of the cortical hexagonal network. Sometimes also, as in the figured specimen, the length of both polar spines is somewhat different.)

Dimensions.—Major axis of the cortical shell 0.15, minor axis 0.12; pores and bars 0.007; main axes of both ellipsoidal medullary shells 0.08 and 0.05; length of the polar spines 0.08 to 0.1, basal breadth 0.02.

Habitat.—Pacific, central area, Stations 266 to 268, depth 2700 to 2900 fathoms.

2. Stylatractus fusiformis, n. sp.

Cortical shell thick walled, smooth, with regular, simple, circular pores, quite as broad as the bars; fourteen to sixteen on the half equator. Polar spines three-sided pyramidal, half as long as the main axis, as broad at the base as the inner medullary shell. (Resembles very nearly Xiphatractus armadillo, Pl. 17, fig. 11, but differs in the regular form and equal length of the polar spines.)

Dimensions.—Major axis 0.17, minor axis 0.13; pores and bars 0.007; main axes of both ellipsoidal medullary shells 0.09 and 0.05; length of the polar spines 0.08, basal breadth 0.04.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, at various depths.

3. Stylatractus compactus, n. sp. (Pl. 17, fig. 4).

Cortical shell thick walled, smooth, with subregular, circular, double-contoured pores, smaller than the bars; sixteen to eighteen on the half equator. The thickness of the shell-wall equals the radius of the inner medullary shell. Polar spines short, three-sided pyramidal; their length and basal thickness variable, but commonly equal to the diameter of the inner medullary shell.

Dimensions.—Major axis 0.16, minor axis 0.13; pores 0.007, bars 0.01; main axes of both ellipsoidal medullary shells 0.09 and 0.04; length and basal breadth of the polar spines 0.04 to 0.05.

Habitat.—Pacific, central area, Stations 270 to 272, depth 2425 to 2925 fathoms.

Subgenus 2. Stylatractylis, Haeckel.

Definition.—Network of the outer shell regular, with meshes of equal size and similar form; surface thorny or papillose, covered with small spinules or tubercles.

4. Stylatractus giganteus, n. sp. (Pl. 17, fig. 1).

Cortical shell papillose, very thick walled, with regular network; pores circular, with double margin, about twice as broad as the bars; ten to twelve on the half equator. The cortical shell is connected with the outer medullary shell by numerous strong beams, and the inner prolongations of both polar spines are much stronger. The circular pores of the outer medullary shell are three times as large as those of the inner, and equal to those of the cortical shell, but the bars are much thinner. Polar spines very strong, three-sided pyramidal, with spirally contorted edges, as long as the main axis, as broad at the base as the inner medullary shell.

Dimensions.—Major axis of the cortical shell 0.3, minor axis 0.22; pores 0.02, bars 0.01; main axes of the ellipsoidal medullary shells 0.14 and 0.07; length of the polar spines 0.3, basal thickness 0.06.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

5. Stylatractus carduus, Haeckel.

Cortical shell thin walled, spiny, with regular, circular pores, five times as broad as the bars; ten to twelve on the half equator. Polar spines conical, half as long as the main axis, at the base broader than the pores. (The cortical shell is ellipsoidal as well as both medullary shells; the figure of Ehrenberg, as is generally the case, is more correct than his description. This interesting species occurs in the Barbados rocks, with double as well as with simple medullary shell, and may in the latter case be distinguished as Lithatractus carduelis.)

Dimensions.—Major axis of the cortical shell 0.12 to 0.16, minor 0.1 to 0.14; pores 0.01 to 0.02, bars 0.002 to 0.005; main axes of the ellipsoidal medullary shells 0.05 and 0.03; length of the polar spines 0.06, basal breadth 0.02.

Habitat.—Fossil in the Tertiary rocks of Barbados.

Subgenus 3. Stylatractona, Haeckel.

Definition.—Network of the outer shell irregular, with meshes of different size or form; surface smooth, without thorns or papillæ.

6. Stylatractus variabilis, n. sp.

Cortical shell thin walled, smooth, with irregular, roundish pores, twice to six times as broad as the bars; twelve to sixteen on the half equator. Polar spines conical, about half as long as the main axis, and as broad at the base as the inner medullary shell. (The size and form of the pores and of the polar spines in this species are very variable, so that the proportions given are to be understood as averages.)

Dimensions.—Major axis 0.13, minor axis 0.11; pores 0.004 to 0.012, bars 0.002; main axes of the ellipsoidal medullary shells 0.07 and 0.04; length of the polar spines 0.06, basal breadth 0.03.

Habitat.—Pacific, central area. Stations 272 to 274, depth 2350 to 2750 fathoms.

7. Stylatractus sethoporus, n. sp. (Pl. 17, figs. 2, 3).

Cortical shell thick walled, smooth, with large irregular, roundish pores, twice to four times as broad as the bars; seven to eight on the half equator. At the bottom of each pore a thin lamella of silex, perforated by four to six irregular, roundish, double-contoured porules. Medullary shells resemble those of Stylatractus giganteus. Polar spines three-sided pyramidal; their length and basal thickness scarcely equal the diameter of the inner medullary shell.

Dimensions.—Major axis 0.15, minor axis 0.13; pores 0.02, bars 0.005, porules 0.01; length of the polar spines 0.04.

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

Subgenus 4. Stylatractium, Haeckel.

Definition.—Network of the outer shell irregular, with meshes of different size and form; surface thorny or papillose, covered with small spinules or tubercles.

8. Stylatractus papillosus, n. sp.

Cortical shell thin walled, with papillose surface, and irregular, simple, roundish pores, ten to sixteen on the half equator, twice to three times as broad as the bars. Conical papillæ of the surface irregularly scattered. Polar spines conical, about as long as the main axis, at the base half as broad as the inner medullary shell.

Dimensions.—Major axis 0.12, minor 0.1; pores 0.006 to 0.01, bars 0.003; main axes of the medullary shells 0.09 and 0.06; length of the polar spines 0.13, basal breadth 0.04.

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

9. Stylatractus disetanius, n. sp.

Cortical shell thin walled, with spiny surface, and irregular, roundish pores, eight to ten on the half equator, twice to three times as broad as the bars. Every pore is divided by thinner bars into four to six small roundish porules. Polar spines three-sided pyramidal, nearly as long as the main axis, as broad at the base as the inner medullary shell. (Resembles Xiphatractus glyptodon, Pl. 17, figs. 9, 10, but differs from it by the irregular network and the equal size of both polar spines.)

Dimensions.—Major axis 0.14, minor 0.1; pores 0.02, bars 0.008, porules 0.007; main axes of the two medullary shells 0.08 and 0.05; length of the polar spines 0.13, basal breadth 0.04.

Habitat.—South Pacific, near New Zealand, Station 169, surface.

Genus 140. Xiphatractus,^[179] n. gen.

Definition.—Druppulida with a simple ellipsoidal cortical shell and double medullary shell, in the main axis with two large opposite polar spines of different size or form.

The genus Xiphatractus differs from the nearly related Stylatractus in the differentiation of two polar spines (in the same manner as Druppatractus differs from Lithatractus). From the spherical Amphistylus it differs in the ellipsoidal form of the cortical shell.

Subgenus 1. Xiphatractara, Haeckel.

Definition.—Network of the cortical shell regular or subregular, with meshes of nearly equal size and similar form; surface smooth, without thorns or papillæ.

1. Xiphatractus armadillo, n. sp. (Pl. 17, fig. 11).

Cortical shell thick walled, smooth, with regular, circular pores, about as broad as the bars; fifteen to sixteen on the half equator. Polar spines three-sided pyramidal, with thick, prominent edges, of irregular form; the longer about as long as the main axis, the shorter scarcely one-third as long; their basal breadth equals the diameter of the inner medullary shell.

Dimensions.—Major axis of the cortical shell 0.13, minor axis 0.1, thickness of its wall 0.01; pores and bars 0.005; main axes of the two medullary shells 0.07 and 0.03; length of the major polar spine 0.12, of the minor 0.04, basal thickness 0.04.

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

2. Xiphatractus euphractus, n. sp.

Cortical shell thick walled, smooth, with regular, circular pores, twice as broad as the bars; eight to nine on the half equator. Each pore has six to nine excisions (commonly eight), elegantly lobed, flower-like (as in Xiphostylus phasianus, Pl. 13, fig. 9). Polar spines strong, angulate; the major pyramidal, longer than the main axis, the shorter elegantly pommel-like, scarcely one-third as long.

Dimensions.—Major axis 0.15, minor 0.12; pores 0.014, bars 0.007; main axes of the two medullary shells 0.09 and 0.05; length of the larger polar spine 0.16, of the shorter 0.05, greatest thickness 0.03.

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

Subgenus 2. Xiphatractylis, Haeckel.

Definition.—Network of the cortical shell regular or subregular, with meshes of nearly equal size and similar form; surface thorny or papillose.

3. Xiphatractus spinulosus, Haeckel.

Cortical shell thin walled, with spiny surface, and large, regular, circular pores, four times as broad as the bars; seven to eight on the half equator. Spines between the pores of the same size, conical. Polar spines also conical, but much larger; the major about as long as the main axis, the minor scarcely half as long; their basal thickness equals the largest pores.

Dimensions.—Major axis 0.1, minor 0.08; pores 0.012, bars 0.003; diameter of the spherical medullary shells 0.06 and 0.03; length of the major polar spine 0.09, of the minor 0.04, basal thickness 0.02.

Habitat.—Fossil in the Tertiary rocks of Barbados.

4. Xiphatractus sulcatus, Haeckel.

Cortical shell thick walled, with thorny surface, and regular, circular pores, quite as broad as the bars; nine to ten on the half equator. Polar spines cylindrical, with longitudinal basal furrows and conical apex, three times as broad as the pores; the larger about as long as the main axis, the shorter only one-half or two-thirds as long.

Dimensions.—Major axis 0.01, minor 0.08; pores and bars 0.007; main axes of the two medullary shells 0.08 and 0.04; length of the major polar spine 0.1, of the minor 0.06, breadth of them 0.02.

Habitat.—Fossil in the Barbados deposits.

5. Xiphatractus dasypus, n. sp.

Cortical shell thick walled, with spiny surface, and regular, elegant network; pores circular, hexagonally framed, about as broad as the bars; from every corner of the network (between three pores) arises a short bristle-like spine. Polar spines three-sided prismatic, as broad as one hexagon; the major once to twice as long as the main axis, the minor only one-half to one-fourth as long. (The cortical shell much resembles Ellipsoxiphus elegans, Pl. 14, fig. 7.)

Dimensions.—Major axis 0.15, minor 0.13; pores and bars 0.01; main axes of the two medullary shells 0.1 and 0.06; length of the major polar spine 0.1 to 0.3, of the minor 0.05 to 0.1, thickness 0.01.

Habitat.—Tropical Western Pacific, Station 222, surface.

Subgenus 3. Xiphatractona, Haeckel.

Definition.—Network of the cortical shell irregular, with meshes of different size or form; surface smooth, without thorns or papillæ.

6. Xiphatractus chlamydophorus, n. sp.

Cortical shell thin walled, smooth, with irregular, roundish pores, twice to four times as broad as the bars; eight to twelve on the half equator. Polar spines angular, irregularly curved or contorted; the larger once to twice as long as the main axis, the shorter and thicker pommel-shaped, only one-third to one-half as long; their basal breadth equals two pores.

Dimensions.—Major axis 0.14, minor 0.1; pores 0.006 to 0.012, bars 0.003; main axis of the two ellipsoidal medullary shells 0.09 and 0.04; length of the major polar spine 0.1 to 0.2, of the minor 0.05 to 0.08, breadth 0.02.

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

Subgenus 4. Xiphatractium, Haeckel.

Definition.—Network of the cortical shell irregular, with meshes of unequal size or dissimilar form; surface thorny or papillose.

7. Xiphatractus radiosus, Haeckel.

Cortical shell very thick walled, with thorny surface, and irregular, roundish pores, once to three times as broad as the bars; nine and ten on the half equator. Polar spines conical, on the base about as broad as the largest pores; the larger as long as the main axis, the smaller scarcely one-fourth as long. (The radial striation, figured by Ehrenberg and applied to the name of this species, is produced by the contours of the funnel-shaped pores in the thick walls seen in optical section; the ellipsoidal cortical shell is double.)

Dimensions.—Major axis 0.13, minor 0.09; pores 0.003 to 0.01, bars 0.003; main axes of the two medullary shells 0.05 and 0.03; length of the major polar spine 0.12, of the minor 0.03, basal breadth 0.01.

Habitat.—Fossil in the Tertiary rocks of Barbados.

8. Xiphatractus glyptodon, n. sp. (Pl. 17, figs. 9, 10).

Cortical shell thick walled, covered with radial spines of the size of the pores; on the half equator eight to ten irregular or subregular roundish pores, twice to four times as broad as the bars. In the bottom of each pore a thin lamella of silex, perforated by four to six smaller roundish pores. Both medullary shells (fig. 10) spherical, with smaller, regular, circular pores. Larger polar spine three-sided pyramidal, in length equals the main axis; shorter spine only half as long, but twice as thick, of elegant pommel-form (fig. 9), with nine prominent edges.

Dimensions.—Major axis 0.12, minor, 0.1; pores and spines 0.01 to 0.02, bars and porules 0.005; diameter of the two medullary shells 0.05 and 0.02; length of the major polar spine 0.1, of the minor 0.06, greatest thickness 0.04.

Habitat.—Pacific, central area, Station 263, surface.

Genus 141. Cromyatractus,^[180] n. gen.

Definition.—Druppulida with four or more concentric shells (two medullary shells and two or more cortical shells), in the main axis with two large opposite polar spines of equal size and similar form.

The genus Cromyatractus is very nearly allied to all the foregoing genera, which bear two equal spines opposite to one another on the poles of the main axis; it differs from them in the multiplication of the cortical shell, and may be considered as the most highly developed form of this amphistylous series, which proceeds from Ellipsoxiphus to Lithatractus and Stylatractus.

Subgenus 1. Cromyatractium, Haeckel.

Definition.—Shell composed of two medullary shells and two cortical shells.

1. Cromyatractus tetraphractus, n. sp. (Pl. 15, fig. 2).

Proportion of the main axes of the four concentric shells about = 1 : 3 : 5 : 7. Network of all four shells nearly of the same structure, subregular, with circular pores of equal size (in one and the same shell). The absolute size of the pores increases gradually from the innermost to the outermost shell. The bars between the pores are smaller and quite smooth. Surface of the outermost shell smooth. Polar spines cylindrical, with conical apex, of variable length, nearly as broad as the innermost shell.

Dimensions.—Main axes of the four shells—(A) inner medullary shell 0.03, (B) outer medullary shell 0.08, (C) inner cortical shell 0.15, (D) outer cortical shell 0.2; equatorial axes of them—(A) 0.025, (B) 0.06, (C) 0.12, (D) 0.15; pores of (A) 0.004, (B) 0.007, (C) 0.01, (D) 0.013, bars 0.002 to 0.004; length of the polar spines 0.1 to 0.3 (and more), breadth 0.015.

Habitat.—Antarctic (Indian) Ocean, Station 157, depth 1950 fathoms.

2. Cromyatractus tetralepas, n. sp.

Proportion of the main axes of the four concentric shells about = 1 : 2 : 4 : 6. Network of the two medullary shells regular, with small circular pores, little larger than the bars. Network of the two cortical shells irregular, with much larger polygonal pores, three to nine times as broad as the thin bars. (Somewhat similar to Cromyatractus ceparius, Pl. 15, fig. 4.) Surface of the outermost shell smooth or a little thorny. Polar spines cylindrical, very large, twice to three times as long as the main axis of the outermost shell, about as broad as the innermost shell, with conical apex; smooth or a little thorny.

Dimensions.—Main axes of the four shells—(A) 0.03, (B) 0.05, (C) 0.13, (D) 0.18; equatorial axes of them—(A) 0.2, (B) 0.45, (C) 0.11, (D) 0.14; pores of the two medullary shells 0.004 and 0.006, of both cortical shells 0.01 to 0.03, bars 0.003.

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

3. Cromyatractus tetracelyphus, n. sp. (Pl. 15, figs. 1, 1a).

Proportion of the main axes of the four concentric shells about = 1 : 3 : 10 : 11. Network of the two spherical medullary shells (fig. 1a) regular, with small circular pores, twice as broad as the bars. Network of the inner cortical shell regular with circular, hexagonally-framed pores, twice as broad as the bars. From every corner of the hexagons (between three pores) arises a very thin, hair-like, short radial spinule. These spinules communicate with one another by tangential branches (at equal distances from the inner cortical shell), and form thereby an outer, delicate cortical network, with large polygonal meshes and very thin bars. Polar spines very strong, pyramidal, with prominent edges, as long as the main radius of the cortical shell, and half as broad at the base.

Dimensions.—Main axes of the four shells—(A) 0.02, (B) 0.06, (C) 0.2, (D) 0.22; equatorial axes of them—(A) 0.02, (B) 0.06, (C) 0.13, (D) 0.15; pores of the four shells—(A) 0.002, (B) 0.004, (C) 0.008, (D) 0.02; bars 0.001 to 0.003; length of the polar spines 0.1, basal breadth 0.05.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

Subgenus 2. Caryatractus, Haeckel.

Definition.—Shell composed of two medullary shells and three or more cortical shells.

4. Cromyatractus cepicius, n. sp. (Pl. 15, fig. 3).

Proportion of the main axes of the five concentric shells about = 1 : 2 : 5 : 7 : 8. Network of both spherical medullary shells regular, with small circular pores, about as broad as the bars. Network of the three ellipsoidal cortical shells irregular, with large polygonal meshes, five to ten times as broad as the thin bars. Surface of the outermost shell smooth. Polar spines cylindrical, thorny, about as thick as the innermost shell and as long as the outermost shell, against the apex with a spindle-like intumescence, formed by delicate spongy framework (fig. 3).

Dimensions.—Main axes of the five concentric shells—(A) 0.03, (B) 0.05, (C) 0.16, (D) 0.2, (E) 0.25; equatorial axes of them—(A) 0.03, (B) 0.05, (C) 0.12, (D) 0.16, (E) 0.2; pores of the two medullary shells 0.002 to 0.004, of the three cortical shells 0.02 to 0.04, bars 0.002; length of the polar spines 0.3, breadth 0.03.

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

5. Cromyatractus ceparius, n. sp. (Pl. 15, fig. 4).

Proportion of the main axes of the six concentric shells about = 1 : 2 : 7 : 10 : 13 : 18. Network of the three inner shells regular, with small, circular pores, which are about as broad as the bars and in the third shell hexagonally framed. Network of the three outer shells irregular, with large polygonal meshes, six to twelve times as broad as the bars. Surface smooth. Polar spines strong, spindle-shaped, thorny, outside of the sixth shell about as long as inside of it; broader than the innermost shell; the thorns of their outer free part (arising at equal distances) represent perhaps the beginnings of three to four further shells.

Dimensions.—Main axes of the six concentric shells—(A) 0.02, (B) 0.05, (C) 0.14, (D) 0.2, (E) 0.26, (F) 0.37; equatorial axes—(A) 0.02, (B) 0.05, (C) 0.09, (D) 0.15, (E) 0.21, (F) 0.3; pores of the three inner shells 0.003 to 0.006, of the three outer shells 0.02 to 0.04, bars 0.003 to 0.005; length of the polar spines, from the base of the innermost shell to the apex, 0.35, greatest breadth 0.03.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

Genus 142. Pipetta,^[181] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and simple medullary shell, with two hollow fenestrated tubes opposite on both poles of the main axis.

The genus Pipetta differs from Pipettella (p. 304) in the possession of an inner (medullary) shell; it exhibits the same tubular prolongations of the cortical shell at both poles of the main axis.

1. Pipetta fusus, n. sp. (Pl. 39, figs. 8, 8a).

Cortical shell spindle-shaped, the middle ellipsoidal part gently passing over on both poles into the conical tubes, which attain about the same length. Network regular, with circular, hexagonally-framed pores, twice as broad as the bars, sixteen to eighteen on the half equator. In the middle part of the shell the pores arise from their hexagonal bases in the form of short conical funnels; on both tubes they are much smaller and simple, without frame. Medullary shell (fig. 8a) spherical, scarcely one-third as broad as the cortical, with regular, circular pores, twice as broad as the bars, eight to nine on the half equator. The two shells are connected only by two opposite beams, lying in the equatorial axis and ramified at the distal insertion (fig. 8a).

Dimensions.—Middle ellipsoidal part of the cortical shell 0.13 to 0.15; polar tubes 0.15 long, 0.06 broad at the base; pores of the former 0.01, bars 0.005; pores of the tubes 0.06, bars 0.003. Medullary shell 0.04, pores 0.004, bars 0.002.

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

2. Pipetta tuba, n. sp. (Pl. 39, fig. 7).

Cortical shell nearly spherical in the middle part, which is sharply separated at both poles from the long, nearly cylindrical tubes; these are longer than the main axis, at the distal end open (always broken off). Network regular, with circular, hexagonally-framed pores, of the same breadth as the bars, eighteen to twenty on the half equator. The pores of the polar tubes are of the same shape, only much smaller, and arranged in sixteen to eighteen longitudinal rows. Medullary shell spherical, about one-third as broad as the cortical, with simple circular pores. The connection between the two shells is only made by two simple opposite beams, lying in the equatorial axis.

Dimensions.—Middle spheroidal part of the cortical shell 0.14 to 0.16; polar tubes 0.15 to 0.2 or longer, 0.03 broad; pores and bars of the former 0.007, of the latter 0.003. Medullary shell 0.04, pores 0.006, bars 0.003.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

3. Pipetta salpinx, n. sp.

Cortical shell ellipsoidal, sharply separated from the cylindrical polar tubes, which reach about the same length (or more). Network regular, with circular pores, three times as broad as the bars, without hexagonal frames, fourteen to fifteen on the half equator. Pores of the polar tubes smaller, arranged in eight to ten longitudinal rows. Medullary shell spherical, one-fourth as broad as the cortical, connected with it by a circle of four to six radial beams, lying in the equatorial plane. Differs from Pipettella prismatica (Pl. 39, fig. 6) in the possession of a medullary shell and the absence of the tube edges.

Dimensions.—Main axis of the ellipsoid 0.14, equatorial axis 0.12, pores 0.01, bars 0.003; length of the tubes 0.15 or more, breadth 0.03. Medullary shell 0.03, pores 0.002, bars 0.001.

Habitat.—Pacific, central area, Stations 265 to 268, depth 2700 to 2900 fathoms.

4. Pipetta conus, n. sp.

Cortical shell spindle-shaped, the middle ellipsoidal part gently passing over at both poles into the conical tubes, which attain only half its length. Network irregular, with roundish or subcircular pores, twice to three times as broad as the bars, twelve to sixteen on the half equator. Medullary shell spherical, one-fourth as broad as the cortical. (Differs from the foregoing species in the short conical tubes and the irregular reticulation.)

Dimensions.—Middle part of the cortical shell 0.16 long, 0.13 broad; tubes 0.09 long, 0.05 on the base broad; pores 0.005 to 0.01, bars 0.003. Medullary shell 0.04.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

Genus 143. Pipettaria,^[182] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and double medullary shell, with two hollow fenestrated tubes opposite on both poles of the main axis.

The genus Pipettaria differs from the foregoing Pipetta only in the duplication of the medullary shell; as in this, the tubular prolongations of the main axis of the cortical shell may be either conical (with closed apex) or cylindrical (with apical opening?).

1. Pipettaria fusaria, n. sp.

Cortical shell spindle-shaped, the middle ellipsoidal part gently passing over on both poles into the conical tubes, which attain about half its length. Pores regular, circular, twice as broad as the bars, sixteen to eighteen on the half equator; pores of the tubes smaller. Both medullary shells spheroidal, compressed. (The appearance of the cortical shell resembles that of Cannartiscus amphiconus, Pl. 39, fig. 19, but without the equatorial constriction.)

Dimensions.—Main axis of the ellipsoid 0.15, equatorial axis 0.13; length of the polar tubes 0.08, basal breadth 0.05; pores of the former 0.008, bars 0.004; diameter of the medullary shells 0.04 and 0.02.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

2. Pipettaria tubaria, n. sp. (Pl. 39, fig. 15).

Cortical shell ellipsoidal, on both poles distinctly separated from the short conical tubes, the length and breadth of which equal the outer medullary shell. In the equatorial plane arises a circle of four to six short conical protuberances, similar to the polar tubes. Pores subregular, circular, or roundish, scarcely broader than the bars, sixteen to twenty on the half equator. Both medullary shells spheroidal, somewhat compressed in the direction of the two poles (as in fig. 18a).

Dimensions.—Main axis of the ellipsoid 0.12, equatorial axis 0.09; pores 0.005, bars 0.004; size of the equatorial protuberances and of the polar tubes 0.02.

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

Family XIII. Spongurida, Haeckel (Pl. 48, figs. 6, 7).

Spongurida, Haeckel, 1862, Monogr. d. Radiol., p. 447 (sensu emendato).

Definition.—Prunoidea with spongy ellipsoidal or cylindrical shell, composed wholly or partially of a spongy framework, without equatorial stricture, with or without an enclosed medullary shell.

The family Spongurida comprises, in the sense here restricted, all those Prunoidea in which the ellipsoidal or cylindrical shell is composed wholly or partially of an irregular siliceous framework, not of simple lattice-work. It contains two subfamilies, differing in the absence or presence of a latticed medullary shell in the middle of the central capsule; in the Spongellipsida it is absent, in the Spongodruppida present; the former are most nearly related to the Ellipsida, the latter to the Druppulida, the difference consisting only in the spongy structure of the cortical shell.

In my Monograph (1862, p. 447) the family Spongurida had a much wider extent, comprising also a number of Sphæroidea and Discoidea, agreeing in the spongy structure of the shell. Here we restrict the definition to those spongy Sphærellaria in which the central capsule and the enclosing spongy cortical shell are ellipsoidal or cylindrical, therefore each transverse section is a circle, and each meridional section an ellipse, as in all Prunoidea.

The Cortical Shell in all Spongurida is composed of a delicate framework of irregularly branched and interwoven siliceous threads; commonly this spongy structure is rather dense or compact, but sometimes also very loose. In the simplest form, Spongellipsis, the spongy cortical shell contains a large cavity, in which lies freely the central capsule. In Spongurus this cavity is completely distended by a spongy framework. In this case the solid spongy shell becomes often prolonged, and its original ellipsoidal form passes over into a cylindrical one (as in many Zygartida). Sometimes (particularly in Spongocore, Pl. 48, fig. 6) the cylinder becomes three-jointed by two more or less distinct annular constrictions. Spongocore is distinguished by an outer veil, a thin lattice-lamella, which envelops the spongy shell and is connected with it by radial beams.

The Medullary Shell, absent in the Spongellipsida, is constant in the second subfamily Spongodruppida. It is either a simple latticed shell (Spongodruppa) or double, composed of two concentric latticed shells (Spongoliva); its form is either spherical or ellipsoidal. It lies in the middle of the central capsule, and is connected by radial beams (perforating the membrane of the latter) with the enveloping spongy cortical shell.

In many Spongurida the surface of the shell is armed with radial spines, and in some genera (Spongoprunum, Spongatractus, &c., Pl. 17, fig. 12), on both poles of the main axis, are developed two strong opposite polar spines, as in many other Prunoidea.

The Central Capsule of the Spongurida is either ellipsoidal or cylindrical. Only in Spongellipsis it lies freely in the internal cavity of the spongy shell. In all other genera it is perforated by a part of the skeleton; in the Spongodruppida it contains the simple or double medullary shell, and the radial beams which perforate its membrane and connect the latter with the external spongy cortical shell. In Spongurus and the allied genera (Spongocore, Spongoprunum) the whole central capsule is filled with a spongy framework which also envelops its surface.

Synopsis of the Genera of Spongurida.

Subfamily 1. Spongellipsida, Haeckel.

Definition.—Spongurida with a spongy ellipsoidal or cylindrical shell, without an internal latticed medullary shell.

Genus 144. Spongellipsis,^[183] n. gen.

Definition.—Spongurida with an ellipsoidal or cylindrical spongy shell, containing an internal cavity, without a latticed medullary shell. Polar spines absent.

The genus Spongellipsis embraces those very simple Spongurida in which the ellipsoidal central capsule is enclosed in a spongy cortical shell of the same form. It corresponds, therefore, to Plegmosphæra among the Sphæroidea, to Plegmodiscus among the Discoidea, and to Spongolarcus among the Larcoidea. In some species the ellipsoidal form is prolonged and passes into a cylindrical one.

Subgenus 1. Spongellipsarium, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial spines.