Legion IV. PHÆODARIA, (continued 2)

Dimensions.—Diameter of the calymma 1.2, of the central capsule 0.22; breadth of the concave caps 0.024, height 0.012.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

Subfamily 3. Dictyochida, Haeckel.

Definition.—Cannorrhaphida with a skeleton composed of numerous annular pieces, which lie tangentially scattered on the surface of the calymma. Each piece is either a simple hollow ring or a pileate and reticulate cap, composed of a ring and several connected bars.

Genus 661. Mesocena,^[279] Ehrenberg, 1841, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 401.

Definition.—Cannorrhaphida with a skeleton composed of simple annular pieces, each of which is a circular, elliptical or polygonal, not fenestrated, ring, with or without radial spines.

The genus Mesocena is the simplest form of the Dictyochida, and no doubt the common ancestral form of this subfamily. The siliceous pieces, which are scattered in variable and indefinite number in the calymma, are simple hollow rings, with or without spines on the periphery. Ehrenberg, who first described and figured such rings (found fossil in different Tertiary rocks) has mistaken them for Diatoms. Some species, which I found in the Challenger preparations, leave no doubt that these rings are the siliceous pieces of the skeleton of the simplest Dictyochida. They are scattered in great numbers in the spherical calymma, which surrounds a tripylean central capsule with all the characters of the Phæodaria. In the living body the rings probably always lie in the spherical periphery of the extracapsular jelly-veil, in tangential planes, whilst in some of the Challenger preparations the rings were scattered in hundreds throughout the whole jelly-mass. In a few species the rings are quite simple, circular or elliptical, smooth, and without teeth or spines. In the majority of species some teeth or radial spines, regularly disposed, arise from the periphery of each ring (two, three, four to eight; sometimes sixteen, eight smaller alternating with eight larger spines). In some species small teeth occur on the inner margin of the rings. The number of radial spines seems to be rather constant in all the rings of one and the same individual, with the exception of a few variations. Thus in Mesocena octogona I found here and there single rings with seven or nine teeth, instead of the usual number eight. Ehrenberg enumerated sixteen different species of Mesocena; many, however, of these are synonymous, being founded on slight variations in the number of the teeth; of others he has given only the name, but neither a figure nor a description (e.g., Mesocena stephanolithis, Mesocena spongolithis, &c.).

1. Mesocena circulus, Ehrenberg.

Mesocena circulus, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 208.

Mesocena circulus, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 44.

Rings of the skeleton circular, smooth or slightly denticulate on the outer margin, without spines. This simple form is probably the ancestral form of the Dictyochida.

Dimensions.—Diameter of the rings 0.02 to 0.03, thickness of the hollow rod 0.001 or less.

Habitat.—Fossil in Tertiary rocks of Barbados and of the Mediterranean (Ægina, Greece; Caltanisetta, Sicily).

2. Mesocena annulus, n. sp.

? Mesocena crenulata, Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 822.

Rings of the skeleton elliptical, smooth or slightly denticulate on the outer margin, without spines. This species is possibly identical with Mesocena crenulata of Ehrenberg, of which, however, no figure is given. The major axis of the ellipse is one and a half times as long as the minor.

Dimensions.—Diameter of the rings in the major axis 0.03, in the minor 0.02; thickness of the bars 0.002.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

3. Mesocena diodon, Ehrenberg.

Mesocena diodon, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 84.

Mesocena diodon, Ehrenberg, 1854, Mikrogeol., Taf. xxxiii., Nr. xv. fig. 18.

Rings of the skeleton elliptical, smooth, with two opposite spines on the poles of the major axis, which is about one and one-third as long as the minor axis.

Dimensions.—Diameter of the rings in the major axis 0.04, in the minor 0.03; length of the spines 0.01.

Habitat.—Fossil in Barbados, and in North America (Virginia).

4. Mesocena triangula, Ehrenberg.

Mesocena triangula, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 208.

Mesocena triangula, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 41.

Dictyocha triangula, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 46.

Lithocircus triangularis, Stöhr, 1880, Palæontogr., vol. xxvi. p. 121, Taf. vii. fig. 10.

Rings triangular, with small peripheral thorns, and three larger teeth on the corners of the equilateral triangle.

Dimensions.—Diameter of the rings 0.03 to 0.05, length of the spines 0.01.

Habitat.—Fossil in Tertiary deposits of the Mediterranean; Caltanisetta, Sicily (Ehrenberg, Stöhr).

5. Mesocena quadrangula, Ehrenberg.

? Mesocena quadrangula, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, pp. 145, 273.

? Mesocena quaternaria, Ehrenberg, 1855, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 302.

Rings square, with four radial spines on the corners of the square. Ehrenberg has given only the name of this species, but neither diagnosis nor figure. I think it may be identical with the species described, which I found in the North Atlantic.

Dimensions.—Diameter of the rings 0.02 to 0.025, length of the spines 0.007 to 0.01.

Habitat.—North Atlantic, Færöe Channel, Gulf Stream (John Murray), depth 600 fathoms.

6. Mesocena elliptica, Ehrenberg.

Mesocena elliptica, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 84.

Mesocena elliptica, Ehrenberg, 1854, Mikrogeol., vol. i. Taf. xx. fig. 44.

Dictyocha elliptica, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 44.

Rings elliptical or ovate, with four peripheral spines which lie in two diameters, perpendicular to one another, two opposite in the major, the two others in the minor axis of the ellipse.

Dimensions.—Diameter of the rings 0.015 to 0.03, length of the spines 0.005.

Habitat.—Fossil in Tertiary rocks of the Mediterranean (Placca di furni, from Zante, Greece); Caltanisetta, Sicily.

7. Mesocena pentagona, n. sp.

Rings regularly pentagonal, with smooth straight bars, and with five short and straight radial spines on the five corners.

Dimensions.—Diameter of the rings 0.02, length of the spines 0.005.

Habitat.—Fossil in Barbados.

8. Mesocena hexagona, Haeckel.

? Mesocena senaria, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, pp. 163, 273.

? Mesocena septenaria, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, pp. 163, 273.

Rings regular, hexagonal, with six radial spines on the six corners (sometimes between the usual six-radiate rings of one and the same individual are intermingled single rings with five or seven spines).

Dimensions.—Diameter of the rings 0.025 to 0.03, length of the spines 0.007 to 0.01.

Habitat.—Mediterranean, Krim (Ehrenberg), Corfu (Haeckel).

9. Mesocena octogona, Ehrenberg.

Mesocena octogona, Ehrenberg, 1841, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 417, Taf. i., Nr. iii. fig. 27.

? Mesocena heptagona, Ehrenberg, 1841, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 417, Taf. i., Nr. iii. fig. 26.

? Mesocena heptagona, Ehrenberg, 1854, Mikrogeol., Taf. xx. fig. 49.

? Mesocena octoradiata, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, pp. 163, 273.

? Mesocena nonaria, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, pp. 163, 273.

Rings regular, octagonal, with eight radial spines on the eight corners of the ring (sometimes between the common octoradiate rings single rings with seven or nine teeth are intermingled in one and the same calymma).

Dimensions.—Diameter of the rings 0.02, length of the spines 0.005.

Habitat.—Tropical Pacific; Peru, Ehrenberg; Station 272 to 274, surface.

10. Mesocena bisoctona, Ehrenberg.

Mesocena bisoctona, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 78; Mikrogeol., Taf. xxxv., Nr. xviii. figs. 9, 10.

Mesocena binonaria, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 78, loc. cit.

Rings circular, with sixteen teeth; eight stronger teeth regularly disposed on the outer margin, alternating with these eight smaller teeth on the inner margin.

Dimensions.—Diameter of the rings 0.02, length of the outer spines 0.005.

Habitat.—Fossil in Guano from Peru and South Africa, also in Barbados.

11. Mesocena stellata, n. sp. (Pl. 101, fig. 9).

Rings circular, with sixteen teeth regularly disposed on the outer margin of the rings, eight stronger teeth alternating with eight smaller.

Dimensions.—Diameter of the rings 0.03, length of the larger spines 0.01.

Habitat.—Central area of the Pacific, Station 270, depth 2925 fathoms.

Genus 662. Dictyocha,^[280] Ehrenberg, 1838, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 128.

Definition.—Cannorrhaphida with a skeleton composed of annular pieces, which are fenestrated by one or more arches, arising on one side of the simple ring, but do not form a truncated pyramid (therefore no apical ring).

The genus Dictyocha is a very remarkable and interesting form of Phæodaria, which has had a curious history. Ehrenberg, who first observed single pieces of it fossil in Tertiary rocks, supposed it to be the siliceous carapace of a Diatom, and gave it the following diagnosis: "Dictyocha, e familia Bacillariorum. Lorica simplex univalvis silicea, laxe reticulata aut stellulata" (loc. cit.). In my Monograph (1862, p. 271), I placed it in the class Radiolaria, supposing that it might be a simple form of Acanthodesmida, having found only isolated siliceous pieces. Afterwards (in 1879) Richard Hertwig observed the entire living body, and demonstrated that the hollow siliceous pieces are scattered in great numbers around a tripylean central capsule, which exhibits all the essential characters of Phæodaria (Organismus d. Radiol., 1879, p. 89). Hertwig describes the position of the numerous siliceous pieces in the surface of the extracapsular jelly-sphere so densely aggregated, that they touch one another and produce the appearance of a reticulated sphere. In two specimens, which I observed living (Pl. 101, fig. 10), and in numerous complete specimens which I found in the collection of the Challenger, the number of the siliceous pieces was much smaller, and they were scattered irregularly in the surface of the alveolate jelly-sphere, being separated by wide and unequal intervals. The regular position seems to be that the basal rings lie tangentially in the spherical surface of the calymma, whilst the bars of the reticulum are directed outwards, and the apical spine radially in centrifugal direction. Very often two pieces are united by their basal rings in such a manner that they form a little spheroidal fenestrated body (as in Distephanus, Stöhr; compare p. 1550). The characteristic reticular skeleton-pieces of Dictyocha must be derived from Mesocena; from its simple siliceous ring (on one side of its plane), arise two, three, or four (rarely more) bars, which become united to a loose framework (with two, three, or four meshes). When this network assumes the form of a truncated pyramid (with a central mesh on the apex), Dictyocha passes over into Distephanus. From the corners of the original basal ring several radial spines usually arise in a centrifugal direction, and on the sides of these sometimes small teeth or thorns also run in a centripetal direction. The number of the meshes and the separating rods is usually four, more rarely two or three. The hollow rods are very thin, either cylindrical or prismatic. As the ascending rods alternate regularly with the corner-spines of the basal ring, we may call the latter perradial, the former interradial. Ehrenberg has distinguished in his genus Dictyocha not less than fifty species, thirty-five living and twenty-five fossil (ten species both living and fossil). The greater part of these cannot be retained, as they are only slight varieties or abnormalities of single pieces of the skeleton, such as very frequently occur associated with the common regular forms in one and the same individual. Such abnormal species are, e.g., Dictyocha abnormis, Dictyocha binoculus, Dictyocha bipartita, Dictyocha haliomma, Dictyocha hexathyra, Dictyocha septenaria, &c. One species (Dictyocha splendens), is the fenestrated calcareous body of a Holothurian. Of some other species Ehrenberg has only given the name, but neither a description nor a figure (e.g., Dictyocha borealis, Dictyocha cenostephania, Dictyocha compos, Dictyocha coronata, Dictyocha socialis, Dictyocha specillum). A number of other species must be placed in the genera Distephanus and Cannopilus, so that only eight of his species of true Dictyocha remain.

1. Dictyocha navicula, Ehrenberg.

Dictyocha navicula, Ehrenberg, 1838, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 129; Mikrogeol., Taf. xx., Nr. i. fig. 43.

Dictyocha ponticulus, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 267.

Each individual ring elliptical or oblong, with one transverse arch in the shorter axis, which bisects it into two meshes. No spines or teeth.

Dimensions.—Diameter of the ring 0.02, of the bars 0.001.

Habitat.—Fossil in Tertiary deposits, Barbados, Sicily, &c.; living in the Atlantic, Stations 352, 354, and off Bermuda, surface.

2. Dictyocha quadrata, Ehrenberg.

Dictyocha quadrata, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 267.

Each individual ring square or rhomboid, with one transverse arch in the shorter axis, forming two meshes. Two peripheral opposite spines on the poles of one axis.

Dimensions.—Diameter of the ring 0.015.

Habitat.—Atlantic, Bermuda Islands; fossil in Barbados.

3. Dictyocha pons, Ehrenberg.

Dictyocha pons, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80; Mikrogeol., Taf. xxi. fig. 40.

Dictyocha tripyla, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80; Mikrogeol., Taf. xxi. fig. 41.

Each individual ring elliptical or oblong, with one transverse arch in the shorter axis, forming two meshes. Four peripheral spines, on the poles of the longer and of the shorter axis. (The individual abnormality, figured as Dictyocha tripyla, loc. cit., Taf. xxi. fig. 41, has the transverse arch bifid at one end, therefore three meshes result; this forms an interesting transition to Dictyocha fibula.)

Dimensions.—Diameter of the ring 0.01, of the bars 0.001.

Habitat.—Fossil in Tertiary rocks, Oran, Africa.

4. Dictyocha triommata, Ehrenberg.

Dictyocha triommata, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 76; Mikrogeol., Taf. xxxiii., Nr. xv. fig. 11.

Dictyocha triactis (= triacantha), Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80.

Dictyocha trifenestrata, Ehrenberg, 1841, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 410; Mikrogeol., Taf. xix. fig. 38.

Dictyocha abyssorum, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 38.

Each pileated piece of the skeleton is a small three-sided pyramid, the sides of which form three triangular meshes; the three edges between them are three curved interradial beams, united in the centre (the apex of the pyramid). Alternating with these, three horizontal, perradial, centrifugal spines start from the base.

Dictyocha trigona, Zittel, 1876 (L. N. 29, p. 83, Taf. ii. fig. 6), is an interesting Cretaceous species, perhaps a variety of Dictyocha triommata.

Dimensions.—Diameter of the basal triangle 0.01, of the three meshes 0.005.

Habitat.—Fossil in different Tertiary deposits (of Sicily, Greece, North America); living in the Central Pacific, Stations 270 to 272, depth 2600 to 2925 fathoms.

5. Dictyocha tripyla, Ehrenberg.

Dictyocha tripyla, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80.

Dictyocha tripyla, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 38 (et Taf. xxi. fig. 41?).

Each pileate piece of the skeleton is a small three-sided pyramid, similar to that of Dictyocha triommata, but differs from it in the possession of three small perpendicular teeth, which are directed downwards and start from the basal ring near the origin of the three horizontal spines.

Dimensions.—Diameter of the triangular basal ring 0.015, of the three meshes 0.007.

Habitat.—Fossil in Tertiary deposits. North Africa (Oran), Sicily (Caltanisetta).

6. Dictyocha medusa, n. sp. (Pl. 101, figs. 13, 14).

Each pileated piece of the skeleton has four equal, cruciate, triangular meshes. From the four corners of the square basal ring proceed four perradial horizontal spines, and between these four interradial curved bars, which correspond to the edges of a four-sided pyramid, arise from the centre of the four sides and become united in the centre (on the apex of the pyramid). No apical spine.

Dimensions.—Diameter of the basal ring 0.02, of the four meshes 0.01.

Habitat.—Central area of the Pacific, Station 272, depth 2600 fathoms.

7. Dictyocha staurodon, Ehrenberg.

Dictyocha staurodon, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80.

Dictyocha staurodon, Ehrenberg, 1854, Mikrogeol., Taf. xviii. fig. 58.

Each pileated piece of the skeleton is a small, regular, four-sided pyramid, similar to the foregoing species. It differs from Dictyocha medusa in the development of a vertical apical spine, and of four small centripetal teeth, which start from the inside of the basal square, between the four perradial spines and the four ascending interradial beams.

Dimensions.—Diameter of the basal ring 0.025, of the meshes 0.01.

Habitat.—Fossil in Tertiary rocks; Tripel of Richmond, Virginia (Ehrenberg); Barbados, (Haeckel); living in the Tropical Atlantic, Station 347, surface.

8. Dictyocha fibula, Ehrenberg.

Dictyocha fibula, Ehrenberg, 1839, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 149; Mikrogeol., Taf. xviii. fig. 54, a, b, c, Taf. xix. fig. 43, Taf. xx. fig. 45, Taf. xxi. fig. 42, &c.

Dictyocha abnormis, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 76; Mikrogeol., 1854, Taf. xxxvA., Nr. xvii. fig. 9.

Dictyocha bipartita, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 44.

Dictyocha tenella, Ehrenberg, 1841, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. ii. fig. 11.

Each pileated piece of the skeleton stirrup-shaped, with two pairs of meshes, and a square basal ring, the four corners of which are prolonged into four perradial spines. Between the latter four interradial beams arise from the sides in pairs, and the two pairs are connected by a diagonal arch. Therefore the two opposite meshes are larger and pentagonal, the other two meshes (alternating with these) are smaller and square. No vertical spine on the apex.

Dimensions.—Diameter of the basal square ring (diagonal) 0.01 to 0.02, of the meshes 0.005.

Habitat.—Fossil in different Tertiary rocks (Barbados, Oran, Greece, Sicily, &c.), Ehrenberg.

9. Dictyocha messanensis, Haeckel.

Dictyocha messanensis, Haeckel, 1862, Monogr. d. Radiol., p. 272, Taf. xii. figs. 3-6.

Dictyocha fibula, R. Hertwig (not Ehrenberg), 1879, Organismus d. Radiol., p. 89, Taf. ix. fig. 5.

Each pileated piece of the skeleton stirrup-shaped, very similar to Dictyocha fibula, but distinguished by a vertical apical spine in the centre of the transverse arch, which connects the two pairs of ascending bars.

Dimensions.—Diameter of the basal ring 0.02 to 0.03, of the meshes 0.01 to 0.016.

Habitat.—Mediterranean (Messina), North Atlantic (Canary Islands), Station 354, surface.

10. Dictyocha epiodon, Ehrenberg.

Dictyocha epiodon, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 79; Mikrogeol., Taf. xviii. fig. 55.

Each pileated piece of the skeleton stirrup-shaped, with four paired meshes similar to the hats of Dictyocha fibula, but distinguished by four small centripetal thorns, which start from the inside of the basal ring, at the side of the four ascending beams. No apical spine.

Dimensions.—Diameter of the basal ring 0.03, of the meshes 0.01.

Habitat.—Fossil in Tertiary rocks of North America (Miocene Tripel of Richmond, Virginia, &c.).

11. Dictyocha stapedia, n. sp. (Pl. 101, figs. 10-12).

Each pileated piece of the skeleton stirrup-shaped, with four paired meshes, similar to the hats of Dictyocha fibula and Dictyocha messanensis, but distinguished by four small centripetal teeth, which start from the inside of the basal ring, at the side of the four ascending beams. In the centre of the diagonal arch arises a vertical apical spine (differing from Dictyocha epiodon). This species seems to be the most common of the living forms and widely distributed over all warmer seas. I observed in Ceylon, taken on the surface, the living specimen figured in Pl. 101, fig. 10, the numerous spicula were irregularly scattered over the spherical surface of the alveolate calymma. Other specimens occur in various preparations of the Challenger collection, from the Atlantic and the Pacific. The majority of the siliceous little hats exhibited the stirrup-form shown in fig. 11, and many were united in pairs, forming a twin-piece (fig. 12). Intermingled with these are found some irregular forms, representing the specific form of some allied species, viz., Dictyocha speculum, Dictyocha staurodon, Dictyocha epiodon and Dictyocha messanensis.

Dimensions.—Diameter of the basal ring 0.015 to 0.03, of the meshes 0.005 to 0.012.

Habitat.—Cosmopolitan; Atlantic, Pacific, Indian Ocean, in the Tropical and warmer regions; Stations 159, 244, 266-272, 318, 352, &c.

12. Dictyocha rhombus, n. sp.

Each pileated piece of the skeleton stirrup-shaped, similar to Dictyocha stapedia, with four paired meshes. It differs from the latter in the rhomboid form of the basal ring and the larger size of the two opposite meshes, which are two to three times as large as the two others. Therefore the four centripetal teeth of the basal ring do not stand in the four single meshes, but in pairs only in the two larger meshes.

Dimensions.—Diameter of the basal ring 0.02, of the meshes 0.005 to 0.01.

Habitat.—North Atlantic; Færöe Channel, Gulf Stream, depth 50 to 600 fathoms, John Murray.

Genus 663. Distephanus,^[281] Stöhr, 1880, Palæontogr., vol. xxvi. Taf. ii. p. 121.

Definition.—Cannorrhaphida with a skeleton composed of pileated pieces, each of which is a small truncated pyramid with one girdle of meshes (the apical ring being simple).

The genus Distephanus was founded in 1880 by Stöhr (loc. cit.) for a single twin-piece of the skeleton of Dictyocha speculum. Among the common fossil forms of this species he once found in the Tertiary rocks of Caltanisetta, Sicily, a single piece (loc. cit., Taf. vi. fig. 9), which seemed to be composed of two equal pieces so united that they formed a little sphere with fourteen meshes; on each pole of the sphere lies a central hexagonal mesh surrounded by six pentagonal meshes, and from the six corners of the equatorial ring arise six centrifugal spines. No doubt this was a mistake, and the apparent little sphere was one of the above mentioned twin-forms, composed of two separate hexagonal truncated pyramids, which were loosely connected by their basal rings. I have often seen such twin-pieces of Dictyocha speculum and of other species (Pl. 101, fig. 12, Pl. 114, fig. 8), and was always able to separate the two loosely connected halves of the bivalve shell by slight compression.

The genus Distephanus of Stöhr, therefore, is nothing other than the Dictyocha of Ehrenberg. But I think it is more convenient to retain the name Distephanus for those forms of Dictyocha which possess a simple apical mesh surrounded by a ring of lateral meshes, and in which each piece of the skeleton forms a small truncated pyramid. The basal plane of this pyramid is marked by the original basal ring (Mesocena), the truncated upper plane by the parallel apical ring, and the edges of the pyramid by the rising bars which connect both rings. In this sense, so far as the two rings lying in parallel planes are concerned, the term Distephanus is correct (but not in the original sense of Stöhr). The number of the rising bars between the two rings varies from four, five, six to eight or more. It seems rather constant in each species, so that all the pieces of the skeleton of one specimen possess either four or six or eight lateral meshes, &c. But sometimes individual irregularities occur. In the majority of species each skeleton-piece is armed with spines. Usually a radial horizontal spine starts centrifugally from each corner of the basal ring, and on the side of this a small tooth or thorn often starts centripetally or downwards. In the twin-pieces, where the two basal rings are united, these teeth catch into one another. In some species upper spines also occur, starting from the corners of the apical ring. The perradial spines of the corners of the basal ring alternate regularly with the interradial ascending bars, which bisect the sides of the ring, as in Dictyocha.

1. Distephanus crux, Haeckel.

Dictyocha crux, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 207; Mikrogeol., 1854, Taf. xviii. fig. 56, Taf. xx. fig. 46, Taf. xxxiii. Nr. xv. fig. 9.

Dictyocha bipartita, Ehrenberg, 1844, loc. cit., p. 79, Taf. xxii. fig. 44.

Each pileated piece of the skeleton exhibits four pentagonal lateral meshes around one square central mesh, and is composed of two horizontal square rings; the smaller upper square is connected with the larger lower square by four ascending interradial beams, which start from the corners of the former and bisect the sides of the latter; from the corners of the basal ring arise four short perradial spines.

Dimensions.—-Diameter of the basal ring 0.02 to 0.03, of the apical ring 0.008.

Habitat.—-Tropical Atlantic, Station 347, surface; fossil in Tertiary deposits of the Mediterranean (Sicily, Oran).

2. Distephanus mesophthalmus, Haeckel.

Dictyocha mesophthalma, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80; Mikrogeol., 1854, Taf. xxii. fig. 43.

Each pileated piece of the skeleton exhibits four lateral meshes around the central mesh, and is composed of two parallel horizontal square rings, like those of Distephanus crux, but distinguished from this by eight short teeth, four centripetal on the larger lower ring and four perradial centrifugal on the smaller upper ring.

Dimensions.—Diameter of the basal ring 0.03, of the apical ring 0.015.

Habitat.—Fossil in Tertiary rocks of Sicily, Caltanisetta (Ehrenberg); living in the Central Pacific, Station 270 to 272, surface.

3. Distephanus stauracanthus, Haeckel.

Dictyocha stauracanthus, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 76; Mikrogeol., 1854, Taf. xxxiii., Nr. xv. fig. 10.

Each pileated piece of the skeleton exhibits four lateral meshes around the central mesh, and is composed of two horizontal rings, which are connected by four perradial beams arising from the corners of the upper and smaller square ring. Lower ring octagonal, with eight peripheral adradial spines, and with four interradial centripetal teeth on the inside.

Dimensions.—Diameter of the basal ring 0.03, of the apical ring 0.004.

Habitat.—Fossil in Tertiary rocks of North America (Hollis Cliff, Virginia; Norwich, Connecticut).

4. Distephanus asteroides, n. sp.

Dictyocha asteroides, Haeckel, 1881, Prodromus.

Each pileated piece of the skeleton exhibits five lateral meshes around the central mesh (or the upper ring). Five peripheral spines (on the corners of the lower ring) simple, not articulated.

Dimensions.—Diameter of the basal ring 0.02, of the apical ring, 0.007.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

5. Distephanus pentasterias, Haeckel.

Dictyocha pentasterias, Ehrenberg, 1839, Mikrogeol., Taf. xviii. fig. 61.

? Dictyocha quinaria, Ehrenberg, 1842, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 265.

? Dictyocha elegans, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80; Mikrogeol., 1854, Taf. xxii. fig. 51.

Actiniscus elegans, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 51.

Each pileated piece of the skeleton exhibits five lateral meshes around the central mesh (or the upper ring). Five peripheral spines (on the corners of the lower ring) articulated, triangular, with three distinct joints (tapering towards the distal end).

Dimensions.—Diameter of the basal ring 0.012 to 0.018, of the apical ring 0.002 to 0.003.

Habitat.—Cosmopolitan; living in the depths of the Atlantic and Central Pacific, Stations 247, 270 to 272, depths 2530 and 2600 to 2925 fathoms; fossil in Tertiary deposits (Tripel of Caltanisetta, Sicily; Richmond, Virginia).

6. Distephanus speculum, Haeckel.

Dictyocha speculum, Ehrenberg, 1837, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 150; Mikrogeol., 1854, Taf. xviii. fig. 57, Taf. xix. fig. 41, Taf. xxi. fig. 44, Taf. xxii. fig. 47, &c.

Dictyocha speculum, Stöhr, 1880, Palæontogr., vol. xxvi., Taf. vii. fig. 8.

Dictyocha anacantha, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 238.

Dictyocha diommata, Ehrenberg, 1854, Mikrogeol., Taf. xxxiii., Nr. xvii. fig. 6.

Dictyocha erebi, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 238.

Dictyocha haliomma, Ehrenberg, 1844, Mikrogeol., 1854. Taf. xxi. fig. 46.

Dictyocha hexathyra, Ehrenberg, 1844, Mikrogeol., 1854, Taf. xxii. fig. 46.

Dictyocha ubera, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80.

Dictyocha stella, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 52.

Dictyocha rotundus, Stöhr, 1880, Palæontogr., vol. xxvi., Taf. vii. fig. 9.

Each pileated piece of the skeleton is a truncated, six-sided pyramid, and composed of two regular hexagonal rings which lie in parallel plains, and are connected by six ascending interradial beams; these start from the corners of the upper smaller ring and bisect the sides of the lower larger ring; from the corners of the latter start six perradial centrifugal spines.

Dimensions.—Diameter of the basal ring 0.03, of the apical ring 0.01.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; fossil in Barbados, Sicily, &c.

7. Distephanus ornamentum, Haeckel.

Dictyocha ornamentum, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80; Mikrogeol., 1854, Taf. xxii. fig. 49.

Dictyocha binoculus, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 79; Mikrogeol., 1854, Taf. xix. fig. 42.

Each pileated piece of the skeleton is a truncated, six-sided pyramid, similar to that of Distephanus speculum, but distinguished by six small (probably vertical) teeth, which start from the inside of the lower (larger) ring, on the sides of the ascending beams.

Dimensions.—Diameter of the basal ring 0.03, of the apical ring 0.015.

Habitat.—Fossil in Tertiary deposits of Sicily, Caltanisetta (Ehrenberg).

8. Distephanus aculeatus, Haeckel.

Dictyocha aculeata, Ehrenberg, 1839, Abhandl. d. k. preuss. Akad. d. Wiss. Berlin, p. 149; Mikrogeol., 1854, Taf. xxii. Fig. 48, Taf. xix. fig. 40.

Dictyocha aculeata, Stöhr, 1880, Palæontogr., vol. xxvi. p. 120, Taf. vii. fig. 7.

Dictyocha bisternaria, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 201.

Each pileated piece of the skeleton is a truncated, six-sided pyramid, similar to that of Distephanus speculum, but distinguished by six small perradial, horizontal teeth, which start from the sides of the upper (smaller) ring.

Dimensions.—Diameter of the basal ring 0.02, of the apical ring 0.008.

Habitat.—Fossil in Tertiary deposits of the Mediterranean; plastic clay of Greece and Sicily; living in the Mediterranean and the Atlantic, Station 352, surface.

9. Distephanus sirius, Haeckel.

Actiniscus sirius, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 68.

Dictyocha sirius, Ehrenberg, 1854, Mikrogeol., Taf. xviii. fig. 59.

Each pileated piece of the skeleton is a truncated six-sided pyramid, similar to that of Distephanus speculum, but distinguished by the six broad, triangular, peripheral spines, which are articulated and connected by a thin siliceous membrane (like a web-membrane); each spine has three articulations (as in Dictyocha pentasterias).

Dimensions.—Diameter of the basal ring 0.02, of the apical ring 0.005.

Habitat.—Fossil in Tertiary rocks (Richmond, Virginia), but also living in the Atlantic Ocean, Gulf Stream, Færöe Channel, John Murray, 1880.

10. Distephanus corona, n. sp. (Pl. 114, figs. 7-9).

Dictyocha corona, Haeckel, 1881, Prodromus.

Each pileated piece of the skeleton is a truncate six-sided pyramid like that of Distephanus speculum, but differing in the number (twenty-four) of teeth or spines. Six interradial ascending beams connect the two horizontal rings between these, and six nearly vertical spines arise from the perradial corners of the upper hexagonal ring. In the same meridional (perradial) plains six larger spines descend downwards from the corners of the lower larger ring. Between these six descending spines and the six ascending beams arise from the upper edge of the lower ring twelve shorter teeth of unequal size (the right tooth in each pentagonal lateral mesh being smaller and directed upwards, the left tooth being larger and directed nearly horizontally outwards). The lower ring is nearly dodecagonal.

Dimensions.—Diameter of the basal ring 0.025 to 0.03, of the apical ring 0.012 to 0.02.

Habitat.—North-west Pacific, Sea of Japan, Station 231, depth 2250 fathoms.

11. Distephanus octonarius, Haeckel.

Dictyocha octonaria, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 201.

Dictyocha polyactis, Ehrenberg, 1844, loc. cit., p. 80; Mikrogeol., 1854, Taf. xxii. fig. 50.

Dictyocha septenaria, Ehrenberg, 1844, loc. cit., p. 80; Mikrogeol., 1854, Taf. xxi. fig. 45.

Each pileate piece of the skeleton is a truncated eight-sided pyramid, composed of two regular octagonal rings, which lie in parallel plains, and are connected by eight radial beams. From the eight outer corners of the lower ring (or from the eight interradial meshes, between the eight perradial beams) start eight basal centrifugal spines. (This species is similar to Distephanus speculum, but has eight beams instead of six. In single pieces the number of the beams and meshes varies between seven and nine, the constant number being eight.) A seven-rayed variety is Dictyocha septenaria (loc. cit.), a nine-rayed Dictyocha polyactis.

Dimensions.—Diameter of the basal ring 0.02 to 0.03, of the apical ring 0.01 to 0.015.

Habitat.—Fossil in Tertiary rocks (Tripel and Marne from Caltanisetta, Sicily; Oran, Africa); living in the depths of the Atlantic, Station 348, and Pacific, Station 270, &c.

12. Distephanus octogonius, n. sp.

Dictyocha septenaria, Ehrenberg, 1854, Mikrogeol., Taf. xxxvA., Nr. xxi. fig. 8.

Each pileated piece of the skeleton is a truncated eight-sided pyramid, like that of Distephanus octonarius, but differs from it by having eight short erect teeth, which arise from the corners of the upper smaller ring and lie in the same perradial plains as the eight horizontal spines starting from the corners of the lower larger ring. Ehrenberg has figured only an individual abnormality with seven beams instead of eight, taken from the Antarctic ice; but I found the same form frequent in deep-sea soundings from the Antarctic, almost constantly with eight beams, isolated hats with six, seven, or nine beams being intermingled.

Dimensions.—Diameter of the basal ring 0.02, of the apical ring 0.012.

Habitat.—Antarctic Ocean; in smolten "Pancake-Ice," taken by Sir James Clark Ross in lat. 78° 10' S., long. 162° W. (Ehrenberg); Station 156, depth 1975 fathoms.

13. Distephanus diadema, n. sp.

Dictyocha diadema, Haeckel, 1881, Prodromus.

Each pileated piece of the skeleton is an eight-sided pyramid, like that of the two foregoing species, but differing in the number and distribution of the teeth or spines, which are thirty-two. From the eight corners of the basal ring start eight long, nearly horizontal perradial spines, which bear on each side a smaller, nearly vertically descending spine. From the eight corners of the upper ring ascend also eight perradial spines, alternating with the eight interradial beams, which connect the two rings.

Dimensions.—Diameter of the basal ring 0.04, of the apical ring 0.02.

Habitat.—South Pacific, Station 293, depth 2025 fathoms.

Genus 664. Cannopilus,^[282] n. gen.

Definition.—Cannorrhaphida with a skeleton composed of pileated pieces, each of which is a small truncated pyramid with two girdles of meshes (the apical ring being fenestrated).

The genus Cannopilus represents the most highly developed form of Dictyochida. Each piece of the skeleton is a little fenestrated hat or topped pyramid, as in Distephanus. But the apical mesh is simple in the latter, in the former it is divided into several meshes by bars which start in a centripetal direction from the upper ring. Therefore we find two annular rows of meshes, one above the other; an apical or upper row of smaller meshes and a basal or lower row of larger meshes. In the apex of the little hat is either a central mesh or an apical spine. Other spines arise from the basal ring, as in the former genera. The number of corner-spines on the basal ring is either four, six, or eight (in individual abnormalities also five or seven).

1. Cannopilus superstructus, Haeckel.

Dictyocha superstructa, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80; Mikrogeol., Taf. xxii. fig. 45.

Each pileated piece of the skeleton is a reticulated four-sided pyramid. The base of it (or the lower ring) is a square, from the four perradial corners of which start four centrifugal horizontal spines. In the centres of the four basal bars (or the sides of the square) arise four interradial beams, which unite in the second (or upper) square ring. This latter forms a second (but much smaller) four-sided pyramid, the apex of which is truncated. Therefore the little hat bears nine meshes; around the large central opening four upper smaller and four lower larger quadrangular meshes.

Dimensions.—Diameter of the basal ring 0.03, of the apical ring 0.01.

Habitat.—Fossil in Tertiary rocks of Sicily (Caltanisetta).

2. Cannopilus diplostaurus, n. sp. (Pl. 114, fig. 10).

Each pileated piece of the skeleton is a truncated quadrangular pyramid. From the corners of the square basal ring start four perradial, nearly horizontal, spines. Between these arise four interradial beams, which are united above by an upper square ring. This latter is divided into four small square meshes by a regular cross of perradial bars, the distal ends of which are prolonged into four short ascending spines. In the centre of the cross arises a vertical apical spine.

Dimensions.—Diameter of the basal ring 0.04, of the apical ring 0.016.

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

3. Cannopilus calyptra, Haeckel.

Dictyocha heptacanthus, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 208; Mikrogeol., 1854, Taf. xix. fig. 39 (?).

Each pileated piece of the skeleton is a truncated six-sided pyramid, like that of Dictyocha speculum, but distinguished by the reticulation of the upper (smaller) ring, which is divided by six beams into six meshes, lying in the horizontal plane of the upper ring. Six peripheral spines on the corners of the lower ring. (The irregular form, figured by Ehrenberg as Dictyocha heptacanthus, loc. cit., is probably only an individual abnormality with seven peripheral spines, instead of six; similar abnormalities occur also among the regular hexagonal forms which I found in the Tertiary rocks of Caltanisetta (Sicily).

Dimensions.—Diameter of the basal ring 0.05, of the apical ring 0.02.

Habitat.—Fossil in Tertiary deposits of Greece and Sicily.

4. Cannopilus hemisphæricus (Haeckel).

Dictyocha hemisphærica, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 266.

Each pileated piece of the skeleton is nearly hemispherical, with thirteen meshes; six lower and larger meshes in the sides of the truncated six-sided pyramid, seven others in the convex surface of the upper ring (one central with six surrounding it). From the six corners of the lower ring arise six horizontal perradial spines. From the inside of the same ring (probably on the side of the six ascending interradial beams) spring six centripetal teeth.

Dimensions.—Diameter of the basal ring 0.02, of the apical ring 0.01.

Habitat.—North Atlantic; Bermuda (Bailey).

5. Cannopilus cyrtoides, n. sp. (Pl. 114, figs. 11, 12).

Dictyocha cyrtoides, Haeckel, 1881, Prodromus.

Each pileated piece of the skeleton is an eight-sided truncated pyramid, or nearly hemispherical. From the basal ring arise twenty-four thorns or teeth, eight longer perradial centrifugal teeth placed almost horizontally, and between these sixteen shorter adradial teeth, directed downwards and somewhat centripetally. The network of the small hat is composed of seventeen meshes, arranged in two rows. The eight lower meshes are hexagonal, separated by six interradial ascending beams, and twice as large as the eight upper pentagonal meshes, which are separated by eight perradial beams, and enclose an apical central mesh.

Dimensions.—Diameter of the basal ring 0.04, of the apical ring 0.005.

Habitat.—Central area of the Pacific, Station 266, depth 2750 fathoms.

Family LXXIII. Aulacanthida, Haeckel (Pls. 102-105).

Definition.—Phæodaria with an incomplete skeleton, composed of numerous hollow radial tubes, which pierce the spherical calymma and touch with their proximal ends the surface of the tripylean central capsule.

The family Aulacanthida represents a large and interesting group of Phæodaria, differing from all other families of this legion in the possession of numerous large radial tubes, which pierce the gelatinous and alveolated calymma in a radial direction, and come in contact with the outer surface of the central capsule by their inner or proximal ends, whilst their outer or distal ends project over the surface of the spherical calymma, and develop a great variety of manifold branches and terminal appendages. Usually (with the exception of a single genus only) the surface of the calymma is covered by an arachnoidal veil or mantle, composed of thousands of very fine, hollow, tangential needles. The skeleton therefore is incomplete, without any direct connection between the isolated pieces, just as in the preceding Cannorrhaphida, but the latter never possess the large, hollow, cylindrical, radial tubes, which are characteristic of all Aulacanthida.

The spherical body of the Aulacanthida has usually a diameter of 1 to 2 mm., and including the radial tubes, of 4 to 5 mm. or more. Some species are very common and cosmopolitan, and some genera contain numerous species, distributed widely over all oceans. In spite of their considerable size and wide distribution, only one species of this great family has been hitherto known, having been discovered by me at Messina in 1859, and described in my Monograph as Aulacantha scolymantha (1862, p. 263, Taf. ii. figs. 1, 2, and Taf. iv. figs. 1-5). I there founded for it the peculiar subfamily Aulacanthida, and annexed it to the Thalassicollida. The same cosmopolitan species has been subsequently observed at Messina by R. Hertwig, who first recognised the three openings in its central capsule, and therefore united it with his Tripylea (Organism. d. Radiol., 1879, p. 88, Taf. ix. figs. 3, 4; Taf. x. figs. 7, 10). The rich collection of the Challenger has added an astonishing number of new and interesting forms of Aulacanthida, so that I can describe here not less than six genera and fifty-eight species. The majority are inhabitants of the colder parts of the South Pacific and South Atlantic, at great depths, whilst a few species only are found in the tropics.

The structure of the body in all Aulacanthida seems to be similar in all important points, and the differences by which we are enabled to separate this great number of species are mainly produced by differences in the development of the radial tubes, their form and their polymorphous apophyses. The entire body represents a rather firm jelly-sphere of 1 to 2 mm. diameter (rarely less or more); the peripheral layer of the spherical calymma is rather clear and transparent, whilst its central part is dark and opaque, containing the big phæodium and the enclosed central capsule. The diameter of the latter is usually between 0.1 and 0.3, often 0.4 to 0.5, or even more. The gelatinous calymma, in the centre of which the capsule is placed, always contains numerous, large, spherical or roundish alveoles, similar to those of Thalassicolla, and between them a delicate network of sarcode (Pl. 102, fig. 1; Pl. 103, fig. 1; Pl. 104, fig. 1).

The spherical surface of the calymma is nearly always protected by that characteristic arachnoidal veil or mantle, which is composed of thousands of very fine tangential needles, densely interwoven in all tangential directions but never directly connected. They are wanting in a single genus only, in Aulactinium (Pl. 101, figs. 6-8). This genus, therefore, may represent a separate subfamily, the Aulactinida, whilst all other genera protected by that mantle constitute the subfamily Aulographida. The tangential needles always seem to have the same shape as I have accurately described, in 1862, of Aulacantha scolymantha. They are constantly smooth, very thin and fragile, but also very elastic cylinders of silica, of equal breadth throughout their whole length, and seem to be open at both ends, since they are easily and constantly filled by air when dried. Their length is usually between 0.2 and 0.3 mm., rarely less than 0.15 or more than 0.5; their diameter is always less than 0.001, usually less than 0.0005.

The large radial tubes of the Aulacanthida constitute the most characteristic structures of this family, and are always so placed that their inner or proximal ends are in loose contact with the outer surface of their central capsule (upon which they rest), whilst their outer or distal ends are more or less prominent over the spherical surface of the calymma. Their position, therefore, is rather loose and movable, since they are fixed only by the consistence of the jelly of the surrounding calymma, and on the surface of the latter by the covering veil or the mantle of tangential needles (compare Pl. 102, fig. 1; Pl. 103, fig. 1; Pl. 104, fig. 1). Their number seems never to be fixed, and is probably very variable in different species. I found, in 1859, in the common Aulacantha scolymantha, the number varying from thirty to one hundred and fifty (loc. cit., p. 264). So also in Aulographis pandora, Aulospathis variabilis, and some other common species, numerous specimens of which I could compare, I found their number very variable, being in one and the same species sometimes only from ten to twenty, at other times from fifty to eighty, and sometimes even from one hundred to one hundred and fifty or more. Perhaps the number increases with the age and the increasing size of the calymma.

The radial tubes are always cylindrical (circular in transverse section), never angular or prismatic. Usually they are straight, more rarely slightly curved (Pl. 105, figs. 1, 2; Pl. 101, fig. 6). The cylinders are usually more or less tapering towards both ends, sometimes even spindle-shaped; the inner or proximal end is always simple and rounded, often slightly swollen or inflated, and ovate; the outer or distal end is often thickened, club-shaped, and exhibits the greatest variety in form and ramification. The length of the radial tubes is usually from 1 to 3 mm., rarely less than 0.8, or more than 3.2; their diameter is usually between 0.02 and 0.03, rarely less than 0.01 or more than 0.05. The smallest radial tubes are found in Aulactinium, the largest in Aulospathis.

The siliceous wall of the cylindrical radial tubes is usually very thin, fragile, and perfectly structureless. Only in a few species, mainly of Aulographis, does the wall become very thick and composed of concentric cylindrical layers (Pl. 105, figs. 6-11). Their cavity is wide and simple, and filled up by jelly (not by sarcode, as I supposed in my first description). The simple cavity of the tubes, though not smaller than in the radial tubes of the Aulosphærida, Circoporida and Tuscarorida, never contains the characteristic axial filament with its branches, which is constantly found in the latter families. According to the description of R. Hertwig, the tubes are perfectly closed and have no opening. I suppose, however, that a small opening always exists in the centre of the rounded base, and perhaps a second on the distal apex. Otherwise the circumstance that the entire and well-preserved tubes become easily and constantly filled up by air, when purified by hot mineral acids and afterwards dried, cannot be explained. I suppose that the jelly contained in the cavity of the tubes remains in constant connection by these openings with the jelly of the surrounding calymma.

The distal ends of the radial tubes exhibit in the Aulacanthida the greatest variety in the production of different branches and capturing apparatus, and this serves for the distinction of the genera and subgenera here described. In two genera only (in Aulactinium Pl. 101, figs. 6-8; and in Aulacantha, Pl. 105, fig. 16), the distal ends are simple, not branched. In the four other genera they are armed with terminal branches, which are usually arranged in elegant verticils. The greatest variety in the formation of these verticils is developed in Aulographis (Pl. 103). The single branches of the terminal verticils are here simple, whilst in the closely allied Auloceros they are forked or elegantly ramified (Pl. 102). Aulospathis, the biggest of all Aulacanthida, is distinguished by the possession of a verticil of lateral branches, placed beyond the terminal verticil, immediately above the veil of tangential needles (Pl. 104). Aulodendron, finally, possesses lateral and terminal branches, which are irregularly scattered.

The branches of the radial tubes are rarely straight, usually more or less curved, either simple or again ramified. Their surface is either smooth or armed with small spines or recurved teeth, often elegantly dentated or serrated (Pl. 103, figs. 20-27; Pl. 105, figs. 7-13). Their distal ends are either simply pointed or armed with a spathilla, or a small crown of verticillate, usually recurved teeth (Pl. 104, figs. 4-17). The variety and elegance of these minute armatures are very interesting, the more so as they occur in very similar and analogous forms among the Aulosphærida, the Cœlographida, and other Phæodaria.

The central capsule of the Aulosphærida and its large nucleus ("Binnenbläschen"), as well as the surrounding alveolate calymma ("Alveolen-Hülle"), and the enclosed dark phæodium ("dunkels Pigment") were first described in my Monograph (1862, loc. cit., p. 362). Their minute structure has been examined afterwards very accurately by R. Hertwig (1879, loc. cit., p. 95). The numerous well-preserved preparations of the Challenger (stained with carmine and preserved in glycerine) which I could examine, confirmed in all respects the detailed description of Hertwig (compare Pl. 102, fig. 1; Pl. 103, fig. 1; Pl. 104, fig. 1).

The spherical or subspherical central capsule is usually slightly depressed in the shortened main axis. Its diameter is usually between 0.1 and 0.3, rarely less than 0.08 or more than 0.4 mm. Its outer membrane (e) is thick and double-contoured, separated by a clear interval from the very thin but firm inner membrane (i). The large astropyle, or the main-opening on the oral pole of the main axis, is closed by a large, convex, radiate operculum (o), from which arises a short tubular proboscis. On both sides of the opposite aboral pole (to the right and left) are two conical parapylæ or secondary openings (u, u). The space between the inner membrane of the capsule and the nucleus is filled up by protoplasm, containing numerous spherical vacuoles of equal size (v); each vacuole encloses a small, dark, fat-granule. The large nucleus (n) is either spherical or lenticular, and more or less depressed in the main axis; its diameter is usually about half as great as that of the enclosing capsule, 0.05 to 0.15, rarely less or more; it contains, enclosed in a clear mass, numerous dark, roundish or oblongish nucleoli (l).

Numerous preparations of Aulacanthida exhibited a central capsule with two nuclei (Pl. 101, fig. 6), or a calymma with two central capsules (Pl. 104, figs. 1, 3); so that the process of propagation by self-division, observed already in many different Phæodaria, seems to happen very frequently in the Aulacanthida. The voluminous phæodium is usually about twice or three times as large as the central capsule, and covers its oral or anterior half; the colour of the roundish phæodella composing it is sometimes more green or brown, at other times more blackish. The roundish alveoles, which fill up the rather firm jelly of the calymma, exhibit nearly the same shape as in the common Thalassicolla nucleata. The surface of the calymma is usually protected by the dense veil of tangential needles, and often forms conical or tent-shaped elevations around the bases of the piercing radial tubes (Pl. 102, fig. 1).

Synopsis of the Genera of Aulacanthida.

Radial tubes simple, without lateral and terminal branches. Surface of the calymma naked, without tangential needles, 665. Aulactinium.

Surface of the calymma covered by a veil of tangential needles, 666. Aulacantha.

Radial tubes without lateral branches, but with a verticil of terminal branches. Terminal branches simple, 667. Aulographis.

Terminal branches forked or again ramified, 668. Auloceros.

Radial tubes with lateral and with terminal branches. Lateral branches verticillate, 669. Aulospathis.

Lateral branches irregularly scattered, not verticillate, 670. Aulodendron.

Radial tubes simple, without lateral and terminal branches.

Surface of the calymma naked, without tangential needles,

665. Aulactinium.

Surface of the calymma covered by a veil of tangential needles,

666. Aulacantha.

Radial tubes without lateral branches, but with a verticil of terminal branches.

Terminal branches simple,

667. Aulographis.

Terminal branches forked or again ramified,

668. Auloceros.

Radial tubes with lateral and with terminal branches.

Lateral branches verticillate,

669. Aulospathis.

Lateral branches irregularly scattered, not verticillate,

670. Aulodendron.

Subfamily 1. Aulactinida, Haeckel.

Definition.—Aulacanthida without external veil of tangential needles on the surface of the calymma.

Genus 665. Aulactinium,^[283] n. gen.

Definition.—Aulacanthida without a veil of tangential needles, with simple radial tubes, which bear neither lateral nor terminal branches.

The genus Aulactinium differs from all the other Aulacanthida in the complete absence of the characteristic fine tangential needles, which constitute in the latter an arachnoidal veil or mantle around the spherical calymma. We accordingly divide the whole family into two subfamilies, the Aulactinida with a naked calymma, and the Aulographida with a veil of tangential needles. The radial tubes possess in the few species of Aulactinium observed a very simple shape, as in the closely allied Aulacantha.

1. Aulactinium actinastrum, n. sp. (Pl. 101, figs. 6, 7).

Radial tubes slenderly spindle-shaped, slightly curved, gradually tapering from the middle towards both ends. The proximal two-thirds of the tubes enclosed in the calymma are smooth; the distal freely prominent third is armed with six to eight equidistant verticils of small conical teeth (ten to fifteen in each verticil).

Dimensions.—Length of the tubes 0.5 to 1.5, breadth 0.02.

Habitat.—South Pacific, Station 289, depth 2550 fathoms.

2. Aulactinium actinelium, n. sp. (Pl. 101, fig. 8).

Radial tubes cylindrical, straight, slightly tapering towards both ends. Proximal two-thirds smooth, the distal third studded with numerous small recurved thorns.

Dimensions.—Length of the tubes 0.6 to 0.9, breadth 0.02.

Habitat.—South Pacific, Station 293, depth 2025 fathoms.

3. Aulactinium actinosphærium, n. sp.

Radial tubes cylindrical, straight, smooth, of nearly equal breadth throughout their whole length, without thorns and spathillæ, pointed at both ends.

Dimensions.—Length of the tubes 1.6 to 2.2, breadth 0.02 to 0.03.

Habitat.—Antarctic Sea, Station 157, depth 1950 fathoms.

Subfamily 2. Aulographida, Haeckel.

Definition.—Aulacanthida with an external veil of interwoven, very numerous and thin, hollow, tangential needles, entirely covering the surface of the calymma.

Genus 666. Aulacantha,^[284] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 799.

Definition.—Aulacanthida with a veil of tangential needles, and with simple radial tubes, which bear neither lateral nor terminal branches.

The genus Aulacantha, hitherto the only representative of this family, was founded by me in 1860 for the cosmopolitan Aulacantha scolymantha, the most common and most widely distributed of all the members of the family. It is the simplest form of the Aulographida, or of those Aulacanthida in which the spherical surface of the calymma is densely covered with interwoven tangential needles. The large radial tubes of Aulacantha possess a very simple shape, as in the preceding Aulactinium, and have neither lateral nor terminal branches.

1. Aulacantha scolymantha, Haeckel.

Aulacantha scolymantha, Haeckel, 1862, Monogr. d. Radiol., p. 263, Taf. ii. figs. 1, 2, Taf. iv. figs. 1-5.

Aulacantha scolymantha, R. Hertwig, 1879, Organism. d. Radiol., p. 88, Taf. ix. fig. 3, Taf. x. figs. 7-10.

Radial tubes cylindrical, straight, of nearly equal breadth throughout their whole length, somewhat inflated on the proximal basal end, smooth throughout the greater part of their length, but in the distal third dentate, with numerous (ten to forty) small pointed teeth, which are curved outwards, and shorter than the thickness of the tube.

Dimensions.—Length of the tubes 0.5 to 2.0, breadth 0.01 to 0.02.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; at many Stations; surface and at various depths; the most common of all Aulacanthida.

2. Aulacantha tubulosa, n. sp.

Radial tubes cylindrical or nearly spindle-shaped, straight, gradually tapering towards the two pointed ends, twice as broad in the middle third as in the outer and inner third, smooth in the inner half, dentate in the outer half, with very numerous (one hundred to two hundred) short conical teeth, which are scarcely one-fourth as large as the greatest breadth of the tube.

Dimensions.—Length of the tubes 0.4 to 0.5, breadth in the middle part 0.02 to 0.03.

Habitat.—Central Pacific, Stations 271 to 274, surface.

3. Aulacantha spinosa, n. sp. (Pl. 105, fig. 4).

Radial tubes cylindrical, straight, of equal breadth throughout their whole length, rounded on the proximal base, smooth in the inner proximal half, dentate or spinescent in the outer distal half, with numerous (fifty to eighty) slender conical teeth, which are curved forwards, increasing in size towards the distal end, and somewhat longer than the breadth of the tube.

Dimensions.—Length of the tubes 0.8 to 1.2, breadth 0.015 to 0.02.

Habitat.—North Pacific, Stations 241 to 253, surface.

4. Aulacantha cannulata, n. sp. (Pl. 105, fig. 16).

Radial tubes cylindrical in the inner proximal half, prismatic in the outer distal half, with from three to six, usually four, prominent, thick, parallel edges, which are dentate towards the thicker distal end; their teeth short, conical, directed outwards, scarcely one-fourth as long as the thickness of the tube. The edges are separated in the distal third by more or less deep furrows, like a channelled column.

Dimensions.—Length of the tubes 1.2 to 2.5, breadth 0.03 to 0.04.

Habitat.—South Pacific, Stations 291 to 293, surface.

5. Aulacantha clavata, n. sp.

Radial tubes more or less irregularly curved, in the inner proximal half slenderly conical, and gradually tapering towards the inflated base, in the outer distal half club-shaped, armed with a few (five to twenty) short conical teeth.

Dimensions.—Length of the tubes 1.0 to 1.2, breadth in the middle pact 0.01, in the distal part 0.04.

Habitat.—South Atlantic, Station 318, depth 2040 fathoms.

6. Aulacantha lævissima, n. sp.

Radial tubes cylindrical, straight, of nearly equal breadth throughout their whole length; the inner proximal end rounded, the outer distal end pointed. Surface of the tubes perfectly smooth, without any teeth. The thickness and length of the simple spicula, as well as the thickness of their wall, are very variable in this species.

Dimensions.—Length of the tubes 0.5 to 4.2, breadth 0.003 to 0.02.

Habitat.—North Atlantic, Station 253, Færöe Channel, surface, John Murray.

Genus 667. Aulographis,^[285] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Aulacanthida with a veil of tangential needles, and with radial tubes, which bear no lateral branches, but at the distal end a verticil of simple terminal branches.

The genus Aulographis, the richest in the number of species among all Aulacanthida, differs from the preceding Aulacantha, its ancestral form, in the development of simple terminal branches, which form either a fork or a verticil. The branches are either smooth or spiny, but not ramified as in the following genus, Auloceros. Their distal ends are either simply pointed or bear a terminal spathilla, or a little crown of recurved teeth. According to these differences we may dispose the twenty-six species described into four subgenera.

Subgenus 1. Aulographantha, Haeckel.

Definition.—Terminal branches of the radial tubes simple, smooth, without lateral teeth and terminal spathillæ. Tubes usually thin and fragile.

1. Aulographis pandora, n. sp. (Pl. 103, figs. 2-9).

Radial tubes cylindrical, slender, straight or slightly curved, of equal breadth. Terminal branches of the tubes very variable in size and number (two to six, usually three or four), without lateral teeth and terminal spathillæ, slender, conical, slightly curved, directed outwards, twice to four times (rarely five to eight times) as long as the breadth of the tubes. This species is extraordinarily variable in the number and size of the simple terminal branches; the eight tubes, shown in figs. 2 to 9, are all found in one and the same specimen.

Dimensions.—Length of the tubes 0.5 to 1.5, breadth 0.01 to 0.03; branches 0.02 to 0.12.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; surface and in various depths.

2. Aulographis bovicornis, n. sp. (Pl. 103, figs. 12-14).

Radial tubes cylindrical, slender, straight, of equal breadth. Terminal branches usually two (rarely three), smooth, without lateral teeth and terminal spathillæ, eight to ten times as long as the breadth of the tube, pointed, S-shaped, or curved like the horns of an ox.

Dimensions.—Length of the tubes 0.6 to 0.8, breadth 0.015 to 0.02; branches 0.1 to 0.2.

Habitat.—South Atlantic (east of Buenos Ayres), Stations 323 to 325, surface.

3. Aulographis taumorpha, n. sp. (Pl. 103, fig. 16).

Radial tubes cylindrical, slender, straight, gradually tapering towards the pointed proximal end. Terminal branches constantly two, opposite in a tangential, slightly concave or nearly straight line, ten to twelve times as long as the breadth of the tube, smooth, straight in the proximal part, recurved in the distal part.

Dimensions.—Length of the tubes 0.7 to 0.8, breadth 0.01 to 0.015; branches 0.1 to 0.15.

Habitat.—North Pacific, Station 231, depth 2250 fathoms.

4. Aulographis triglochin, n. sp. (Pl. 103, fig. 17).

Radial tubes robust, club-shaped at the distal end. Terminal branches three (rarely two or four), widely divergent, geniculated and recurved, smooth, without lateral teeth and terminal spathillæ.

Dimensions.—Length of the tubes 1.2 to 1.8, breadth 0.02; branches 0.12 to 0.15.

Habitat.—Central Pacific, Stations 271 to 274, surface.

5. Aulographis cruciata, n. sp. (Pl. 103, fig. 25).

Radial tubes slender, cylindrical, of equal breadth. Terminal branches almost constantly four, equal, regularly crossed (very rarely three or five), slender, straight or slightly curved, smooth, divergent outwards, six to eight times as long as the breadth of the tube.

Dimensions.—Length of the tubes 1.0 to 1.5, breadth 0.02; branches 0.12 to 0.15.

Habitat.—South Atlantic, Stations 325 to 332, surface.

6. Aulographis ancorata, n. sp. (Pl. 103, fig. 21).

Radial tubes slender, cylindrical, straight. Terminal branches constantly four, equal, regularly crossed, arcuato-recurved or nearly semicircular, smooth, six to eight times as long as the breadth of the tube. Resembling an anchor with four teeth.

Dimensions.—Length of the tubes 0.5 to 0.7, breadth 0.012 to 0.015; branches 0.07 to 0.09.

Habitat.—South-west Atlantic, Station 318, depth 2040 fathoms.

7. Aulographis stellata, n. sp. (Pl. 103, figs. 23, a-c).

Radial tubes club-shaped, gradually thickened towards the distal end. Terminal branches stellate, numerous (five to ten or more), diverging in all directions, smooth, straight or slightly curved, slenderly conical, three to five times as long as the distal breadth of the tube. The branches are very variable in size, sometimes very small (figs. a, b).

Dimensions.—Length of the tubes 0.4 to 0.8, breadth 0.02; branches 0.01 to 0.02.

Habitat.—Indian Ocean, Madagascar (Rabbe), surface.

8. Aulographis penicillata, n. sp.

Radial tubes slender, cylindrical, of equal breadth. Terminal branches pencil-shaped, smooth, very numerous (twenty to thirty or more), diverging outwards, curved, eight to ten times as long as the breadth of the tube, very thin and fragile, resembling a brush.

Dimensions.—Length of the tubes 1.0 to 1.5, breadth 0.02; branches 0.15 to 0.2.

Habitat.—North Atlantic (Antilles), Weber, surface.

9. Aulographis pistillum, n. sp. (Pl. 105, fig. 6).

Radial tubes club-shaped, robust, straight, gradually thickened towards the distal end. Terminal branches eight to ten (usually nine), conical, smooth, slightly curved, divergent outwards like a regular corona.

Dimensions.—Length of the tubes 0.5 to 0.6, distal breadth 0.04; branches 0.08.

Habitat.—North Atlantic, Station 354, depth 1675 fathoms.

Subgenus 2. Aulographella, Haeckel.

Definition.—Terminal branches of the radial tubes without terminal spathillæ, but with lateral teeth or secondary spines. (Tubes usually very stout and robust, club-shaped.)

10. Aulographis triæna, n. sp. (Pl. 105, fig. 8).

Radial tubes club-shaped, straight, tapering gradually towards the rounded proximal end. Terminal branches constantly three, divergent, very stout, eight to ten times as long as the breadth of the tube, each studded with three to six irregular, conical, secondary spines. Sometimes the branches become forked, the species passing over into Auloceros cervinus.

Dimensions.—Length of the tubes 1.2 to 1.5, breadth 0.004 to 0.06; branches 0.3 to 0.5.

Habitat.—South Pacific, Station 299, depth 2160 fathoms.

11. Aulographis martagon, n. sp. (Pl. 105, fig. 7).

Radial tubes club-shaped or slenderly conical, strongly thickened towards the distal end. Terminal branches six to nine, conical, slightly curved, divergent outwards, studded outside with small, conical, secondary spines, twice to three times as long as the breadth of the tube.

Dimensions.—Length of the tubes 1.0 to 1.2, breadth 0.04 to 0.05; branches 0.1 to 0.15.

Habitat.—South Atlantic, Station 318, depth 2040 fathoms.

12. Aulographis flammabunda, n. sp. (Pl. 105, fig. 9).

Radial tubes club-shaped, more or less curved, with thickened distal ends. Terminal branches three to six, conical, very stout, three to four times as long as the breadth of the tube, densely studded with numerous, crowded, conical, secondary spines, which are very irregular and more or less curved, resembling the flames of a fire.

Dimensions.—Length of the tubes 1.0 to 1.2, distal breadth 0.08 to 0.1; branches 0.2 to 0.4.

Habitat.—South Pacific, Station 302, depth 1450 fathoms.

13. Aulographis gemmascens, n. sp. (Pl. 105, fig. 11).

Radial tubes club-shaped, more or less curved, with thickened distal end. Terminal branches three to nine (usually three larger and six smaller) stout, conical, studded with irregular, straight, conical, secondary spines, crowded and densely aggregated, like the leaves in a bud.

Dimensions.—Length of the spines 1.5 to 1.8, distal breadth 0.07 to 0.1; branches 0.2 to 0.6.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

14. Aulographis flosculus, n. sp. (Pl. 105, fig. 10).

Radial tubes club-shaped, straight, tapering gradually towards the rounded proximal end. Terminal branches nine to twelve, stout, conical, twice to three times as long as the breadth of the tube, studded with irregular secondary spines, connected in the proximal half by a solid, cap-shaped, flinty lamella, so that the terminal corona resembles a flower. The hollow canal of the tube sends a thin branch into each branch of the crown.

Dimensions.—Length of the tubes 1.2 to 1.8, distal breadth 0.04 to 0.05; branches 0.1 to 0.2.

Habitat.—North Atlantic, Færöe Channel (Gulf Stream), John Murray, depth 600 fathoms.

Subgenus 3. Aulographidium, Haeckel.

Definition.—Terminal branches of the radial tubes armed with terminal spathillæ (or whorls of small radial teeth), but without lateral denticles or spines.

15. Aulographis furcula, n. sp. (Pl. 103, figs. 10, 11).

Radial tubes cylindrical, slender, slightly curved. Terminal branches usually two, sometimes on single tubes three, eight to ten times as long as the tube is broad, strongly curved, ascending vertically from a horizontal base, with a terminal spathilla of four crossed teeth at the distal end.

Dimensions.—Length of the tubes 0.6 to 0.8, breadth 0.006 to 0.008; branches 0.06 to 0.08.

Habitat.—North-west Pacific (off Japan), Station 231, depth 2250 fathoms.

16. Aulographis triangulum, n. sp. (Pl. 103, fig. 15).

Radial tubes cylindrical, slender, straight. Terminal branches constantly three, slender, slightly curved, nearly horizontally (tangentially) expanded, eight to ten times as long as the tube is broad, with a terminal spathilla of four recurved teeth which are opposite in pairs. Since the angles between the three branches are equal (= 120°) they correspond to the axes of an equilateral triangle.

Dimensions.—Length of the tubes 1.2, breadth 0.015 to 0.02; branches 0.1 to 0.12.

Habitat.—South Pacific, Station 289, depth 2550 fathoms.

17. Aulographis tetrancistra, n. sp. (Pl. 103, fig. 22).

Radial tubes slender, cylindrical, straight. Terminal branches four to six (usually four), eight to ten times as long as the tube is broad, slightly curved and widely divergent, with a terminal spathilla of four crossed recurved teeth.

Dimensions.—Length of the tubes 0.5 to 0.7, breadth 0.01; branches 0.08 to 0.1.

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

18. Aulographis hexancistra, n. sp. (Pl. 103, figs. 18, 19).

Radial tubes club-shaped, slightly curved, gradually thickened from the proximal to the distal end. Terminal branches four to eight (usually six in the majority of tubes), widely divergent, nearly straight, three to four times as long as the tube is broad, with a terminal spathilla of six (rarely five) recurved teeth.

Dimensions.—Length of the tubes 0.4 to 0.6, breadth 0.01 to 0.02; branches 0.04 to 0.08.

Habitat.—North Pacific, Stations 244 to 253, depth 2050 to 3125 fathoms.

19. Aulographis polyancistra, n. sp.

Radial tubes club-shaped, straight, thickened towards the distal end. Terminal branches ten to twenty, smooth, strongly curved, disposed in a corona, six to eight times as long as the tube is broad, each with a terminal spathilla of eight to twelve radial teeth.

Dimensions.—Length of the tubes 0.6 to 0.8, distal breadth 0.02; branches 0.12 to 0.16.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

20. Aulographis asteriscus, n. sp. (Pl. 103, fig. 24).

Radial tubes slender, cylindrical, straight, equally broad. Terminal branches six to nine, widely divergent, disposed in a radiate corona, around a central branch, which is the distal prolongation of the tube itself. Each branch bears a stellate terminal spathilla, composed of ten to twenty conical teeth, which radiate in all directions.

Dimensions.—Length of the tubes 0.5 to 0.8, breadth 0.02; branches 0.06 to 0.09.

Habitat.—South Atlantic, Station 318, depth 2040 fathoms.

Subgenus 4. Aulographonium, Haeckel.

Definition.—Terminal branches of the radial tubes armed with numerous lateral denticles, and with terminal spathillæ (or whorls of small radial teeth).

21. Aulographis dentata, n. sp. (Pl. 103, fig. 20).

Radial tubes slender, cylindrical, equally broad, scarcely inflated at the distal end. Terminal branches six to eight, curved, disposed in a corona around a straight central branch, eight to ten times as long as the tube is broad, armed with numerous stout recurved lateral denticles and with a terminal spathilla of five or six recurved teeth.

Dimensions.—Length of the tubes 1.5 to 2.5, breadth 0.03; branches 0.15 to 0.2 long.

Habitat.—North Atlantic, Station 354, depth 1675 fathoms.

22. Aulographis pulvinata, n. sp. (Pl. 103, fig. 26).

Radial tubes club-shaped, straight, gradually thickened towards the distal end, which bears a broad, circular, biconvex cushion. The margin of this cushion bears two alternating verticils of radially divergent, straight, terminal branches, which are twice to three times as long as the tube is broad. Each branch is armed with two opposite lateral rows of numerous small denticles, and bears a terminal spathilla with six to eight recurved radial teeth.

Dimensions.—Length of the tubes 2.0 to 2.4, distal breadth 0.03 to 0.07; branches 0.05 to 0.08 long.

Habitat.—South-east Pacific (off Valparaiso), Station 298, depth 2225 fathoms.

23. Aulographis tripentas, n. sp. (Pl. 105, fig. 13, 13a).

Radial tubes club-shaped, straight, thickened towards the inflated distal end, which bears three alternating verticils of terminal branches, each with five radial branches. The ten branches of the inner and outer verticils are perradial, smooth; the alternating five branches of the middle verticil are armed with recurved lateral denticles. Each of the fifteen branches bears a terminal spathilla with five to seven recurved teeth.

Dimensions.—Length of the spines 2.0 to 2.5, distal breadth 0.03 to 0.06; branches 0.1 long.

Habitat.—South-east Pacific (off Juan Fernandez), Station 299, depth 2160 fathoms.

24. Aulographis verticillata, n. sp. (Pl. 105, fig. 12, 12a).

Radial tubes cylindrical, equally broad, with an inflated ellipsoidal knob at the distal end. This knob bears twenty to thirty slender, slightly curved, terminal branches, which are regularly arranged in five radial or meridional rows, and in four to six concentric verticils. The branches are five to ten times as long as the tube is broad, and armed with two opposite rows of lateral denticles, and with a terminal spathilla of six to eight recurved teeth.

Dimensions.—Length of the tubes 1.5 to 1.8, breadth 0.01 to 0.02; branches 0.5 to 1.0 long.

Habitat.—South Pacific, Station 293, depth 2025 fathoms.

25. Aulographis serrulata, n. sp. (Pl. 103, fig. 27).

Radial tubes club-shaped, curved, thickened towards the inflated ellipsoidal distal end, which bears a bunch of fifteen to twenty-five terminal branches, arranged more or less regularly in radial or meridional rows and concentric horizontal verticils. The branches are irregularly curved, twice to four times as long as the distal end of the tube, armed with two opposite rows of lateral denticles, and at the distal end with a spathilla of six radial teeth.

Dimensions.—Length of the tubes 1.5 to 1.8, breadth 0.02 to 0.04; branches 0.1 to 0.15 long.

Habitat.—North Pacific, Stations 253 and 254, depth 3025 to 3125 fathoms.

26. Aulographis candelabrum, n. sp. (Pl. 103, fig. 1).

Radial tubes club-shaped, straight, thickened towards the distal end and constricted beyond the ovate, inflated, terminal knob. This knob is similar to a candelabrum and bears a corona of six to nine strongly curved terminal branches, which are eight to ten times as long as the tube is broad, armed with scattered lateral denticles, and with a spathilla of five to seven radial teeth.

Dimensions.—Length of the tubes 1.6 to 2.4, breadth 0.03 to 0.05; branches 0.2 to 0.3 long.

Habitat.—South-east Pacific (off Juan Fernandez), Station 300, depth 1375 fathoms.

Genus 668. Auloceros,^[286] n. gen.

Definition.—Aulacanthida with a veil of tangential needles, and with radial tubes, which bear no lateral branches, but at the distal end a verticil of ramified or forked terminal branches.

The genus Auloceros differs from the preceding closely allied Aulographis, its ancestral form, in the ramification of the verticillate terminal branches. They are either simply forked or again ramified, and their distal ends are either simply pointed or armed with a terminal spathilla, or a little crown of recurved teeth. Some forms of this genus belong to the most elegant and graceful Phæodaria, as the Auloceros elegans figured, which I observed living in the Indian Ocean.

Subgenus 1. Auloceræa, Haeckel.

Definition.—Distal ends of the terminal branches pointed, smooth, without spathilla (or corona of radiate denticles).

1. Auloceros furcosus, n. sp. (Pl. 102, figs. 2-6).

Radial tubes slender, spindle-shaped or nearly cylindrical, more or less tapering towards the two ends. Terminal branches slender, curved, twice to four times as long as the tube is broad, very variable in number (usually two or three, rarely four, five, or six; compare figs. 2-6), once or twice forked; the secondary branches are short, irregular, and pointed. No terminal spathillæ. In some specimens of this species all the tubes bear two or three terminal branches, whilst in others there are tubes with four, five, or six branches intermingled. When the number of the terminal branches is constant in single localities, this transformistic or "Darwinian" species may be divided into the following "subspecies:" (1) Auloceros pandora (with variable numbers); (2) Auloceros bifurca (fig. 2); (3) Auloceros trifurca (fig. 3); (4) Auloceros quadrifurca (fig. 4); (5) Auloceros quinquefurca (fig. 5); (6) Auloceros sexfurca (fig. 6).

Dimensions.—Length of the tubes 1.5 to 2.5, breadth 0.02 to 0.03; branches 0.05 to 0.15 long.

Habitat.—North Pacific, Stations 231 to 253, surface and at various depths.

2. Auloceros trigeminus, n. sp. (Pl. 102, fig. 7).

Radial tubes club-shaped, gradually thickened towards the inflated distal end. Terminal branches short, scarcely longer than the tube is broad, two constantly opposite, each with three equal, conical, short secondary branches. No terminal spathillæ.

Dimensions.—Length of the tubes 0.6 to 0.8, breadth 0.02 to 0.03; branches 0.04 to 0.08.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

3. Auloceros capreolus, n. sp. (Pl. 102, fig. 8).

Radial tubes cylindrical, equally broad. Terminal branches in two opposite clustered bunches, each with sixteen to eighteen unequal secondary branches. The total length and breadth of each cluster is about four times as great as the tube is broad. No terminal spathillæ.

Dimensions.—Length of the tube 1.5 to 2.0, breadth 0.03; branches 0.07 to 0.1.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

4. Auloceros cervinus, n. sp. (Pl. 102, figs. 9, 10).

Radial tubes slender, spindle-shaped, slightly curved, tapering gradually from the middle towards the two ends. Terminal branches constantly three, obliquely ascending, each twice or three times forked (often more or less irregularly), with slender, curved, secondary and tertiary branches (twenty to twenty-four on each tube); the latter are scarcely half as broad as the three main branches of each tube. No terminal spathillæ.

Dimensions.—Length of the tubes 2.0 to 3.5, breadth 0.03 to 0.04; branches 0.12 to 0.15 long.

Habitat.—South Atlantic, Station 325, depth 2650 fathoms.

5. Auloceros elegans, n. sp. (Pl. 102, fig. 1).

Radial tubes slender, cylindrical, straight, equally broad. Terminal branches two or three, more or less irregularly branched, each with twelve to eighteen curved and pointed secondary branches. No terminal spathillæ. Differs from the preceding Auloceros cervinus in the cylindrical form of the thinner straight tubes, and the more irregular ramification; the branches are nearly tangentially expanded, The specimen figured, with expanded pseudopodia, red central capsule, and green phæodium, was observed living by me in 1882 in Ceylon.

Dimensions.—length of the tubes 1.0 to 2.0, breadth 0.02 to 0.03; branches 0.15 to 0.3.

Habitat.—Indian Ocean, Ceylon (south of Matura), Haeckel, surface.

Subgenus 2. Auloceratium, Haeckel.

Definition.—Distal ends of the terminal branches with a spathilla, or a small corona of radial, usually recurved teeth.

6. Auloceros dicranaster, n. sp. (Pl. 105, figs. 14, 15).

Radial tubes cylindrical, straight, equally broad. Terminal branches tangential, forked, expanded horizontally, five to six times as long as the tube is broad; their number is usually five (more rarely four or six), and each is divided into two short, equal, divergent, secondary branches, armed at the distal end with a spathilla of five or six unequal recurved teeth.

Dimensions.—Length of the tubes 1.0 to 1.5, breadth 0.01 to 0.02; branches 0.05 to 0.08.

Habitat.—North Pacific, Stations 244 to 252, depth 2050 to 3050 fathoms.

7. Auloceros spathillaster, n. sp. (Pl. 102, fig. 12).

Radial tubes club-shaped or nearly cylindrical, straight, often thickened towards the distal end. Terminal branches ascending, three to six, usually four, partly simple, partly forked, slightly curved. The branches are from twice to three times as long as the tube is broad, and much thinner; at the distal end they are armed with a spathilla of five or six recurved teeth.

Dimensions.—Length of the tubes 2.0 to 2.5, breadth 0.02 to 0.03; branches 0.08 to 0.12.

Habitat.—South Atlantic, Station 319, depth 2425 fathoms.

8. Auloceros arborescens, n. sp, (Pl. 102, figs. 11, 13).

Radial tubes club-shaped, irregularly curved, thickened towards the distal end. Terminal branches two opposite (rarely three or four), forked near the base, and either dichotomously or more irregularly branched; each tube bears fifteen to thirty, usually twenty to twenty-four, secondary branches, which are irregularly curved, and armed at the distal end with a spathilla of four to eight recurved teeth. The tubes are more richly branched than in the preceding, smaller, closely allied species, and the branches are more flatly expanded.

Dimensions.—Length of the tubes 2.6 to 3.3, breadth 0.03 to 0.04; branches 0.1 to 0.2.

Habitat.—South Pacific, Stations 288 to 295, depth 1500 to 3000 fathoms.

Genus 669. Aulospathis,^[287] n. gen.

Definition.—Aulacanthida with a veil of tangential needles, and with radial tubes, which bear two verticils of branches, a distal verticil of terminal branches, and a proximal verticil of lateral branches.

The genus Aulospathis and the following Aulodendron differ from the preceding Aulacanthida in the possession of lateral branches; these are usually similar to the terminal branches, and irregularly scattered along the distal half of the tubes in Aulodendron. In Aulospathis, however, the largest form in the family, each tube bears two whorls or verticils only, a verticil of terminal branches at the distal end, and a verticil of lateral branches beyond the latter, between the middle and distal third of the tube. The number of branches in each verticil is usually from two to four, rarely more; it is, however, very variable, so that the ten species described in the sequel are "Darwinian species," derived either from Aulospathis polymorpha, or from Aulospathis variabilis. Each branch bears at the distal end a spathilla, the teeth of which are very variable in form, number and arrangement.

Subgenus 1. Aulospathessa, Haeckel.

Definition.—Distal ends of the radial tubes inflated, usually in the form of an ovate or pyriform terminal knob.

1. Aulospathis bifurca, n. sp. (Pl. 104, figs. 1-5).

Radial tubes with an inflated ovate terminal knob at the distal end, which bears two divergent, curved, terminal branches (often a few tubes bear three or four branches instead of the usual two). Proximal whorl usually cruciate, with four irregularly crossed lateral branches (but often with five or six, more rarely with two or three).

Dimensions.—Length of the tubes 0.15 to 25 mm., breadth 0.04 to 0.06; branches 0.1 to 0.15.

Habitat.—South Pacific, Stations 293 to 295, depth 1500 to 2270 fathoms.

2. Aulospathis trifurca, n. sp. (Pl. 104, figs. 6, 7, 7a).

Radial tubes with an inflated ovate terminal knob at the distal end, which bears three divergent, straight, or slightly curved terminal branches (often a few tubes bear two or four branches instead of the usual three). Proximal whorl irregular, usually with six divergent, straight, lateral branches.

Dimensions.—Length of the tubes 2.2 to 3.4, breadth 0.03 to 0.05; branches 0.1 to 0.15.

Habitat.—South Pacific (off Valparaiso), Stations 298 to 300, depth 1375 to 2225 fathoms.

3. Aulospathis quadrifurca, n. sp.

Radial tubes with an inflated ovate terminal knob at the distal end, which bears four crossed, divergent, curved terminal branches. Proximal whorl also rather regular, with a cross of four straight lateral branches.

Dimensions.—Length of the tubes 3.0 to 4.0, breadth 0.04 to 0.08; branches 0.2 to 0.3.

Habitat.—South Pacific, Station 291, depth 2250 fathoms.

4. Aulospathis polymorpha, n. sp. (Pl. 104, figs. 10-13).

Radial tubes with an inflated ovate terminal knob at the distal end, which bears a variable number of divergent, curved, irregular, terminal branches. Usually the majority of the tubes bear three branches, whilst others exhibit two or four, sometimes also five or six. Proximal whorl also very variable and irregular, with two to six, usually three or four unequal branches.

Dimensions.—Length of the tubes 2.0 to 4.0, breadth 0.04 to 0.06; branches 0.1 to 0.3.

Habitat.—South Pacific, Station 289, depth 2550 fathoms.

Subgenus 2. Aulospathilla, Haeckel.

Definition.—Distal ends of the radial tubes of equal breadth or tapering gradually, not inflated, without terminal knobs.

5. Aulospathis diodon, n. sp.

Radial tubes without inflated terminal knob, forked at the tapering distal end, with two divergent curved branches of equal size. Proximal whorl cruciate, with four rather equal, crossed, straight, lateral branches (sometimes three or five instead of four in single tubes).

Dimensions.—Length of the tubes 2.0 to 2.5, breadth 0.03 to 0.04; branches 0.1 to 0.3.

Habitat.—North Pacific, Station 231, depth 2250 fathoms.

6. Aulospathis triodon, n. sp. (Pl. 104, fig. 8).

Radial tubes without inflated terminal knob, with three divergent, slightly curved, terminal branches. Proximal whorl with a variable number of curved lateral branches, usually also three (often two or four, rarely more).

Dimensions.—Length of the tubes 2 to 3, breadth 0.03 to 0.05; branches 0.2 to 0.3.

Habitat.—North Pacific, Stations 250 to 253, depth 2740 to 3125 fathoms.

7. Aulospathis tetrodon, n. sp. (Pl. 104, fig. 9).

Radial tubes without inflated terminal knob, with four crossed, divergent, slightly curved terminal branches. Proximal whorl usually with an irregular cross of four lateral branches (often five or six, rarely two or three instead of the usual four).

Dimensions.—Length of the tubes 2.0 to 2.5, breadth 0.03 to 0.04; branches 0.2 to 0.3.

Habitat.—North Pacific, Stations 244 to 245, depth 2775 to 2900 fathoms.

8. Aulospathis hexodon, n. sp.

Radial tubes without inflated terminal knob, with three forked, curved branches at the distal end, so that each tube usually bears six terminal branches; but other tubes of the same specimen bear only three simple or a few irregularly forked branches. Proximal whorl usually with six curved, irregular, lateral branches.

Dimensions.—Length of the tubes 2.0 to 3.0, breadth 0.03 to 0.06; branches 0.2 to 0.5.

Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.

9. Aulospathis furcata, n. sp.

Radial tubes without inflated terminal knob, with a variable number of unequal terminal branches, which are partly simple, partly irregularly forked or branched; the usual number of terminal branches is three or four, more rarely two or five or six. Proximal whorl very irregular, usually with four to six unequal, lateral branches.

Dimensions.—Length of the tubes 2.0 to 2.5, breadth 0.03 to 0.05; branches 0.1 to 0.3.

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

10. Aulospathis variabilis, n. sp. (Pl. 104, figs. 14-17).

Radial tubes without inflated terminal knob, with a variable number of unequal terminal branches, which are constantly simple, never forked; the usual number is in the majority of the tubes three or four, often also two, rarely five to eight. Proximal whorl irregular, with a variable number of lateral branches (usually four to six).

Dimensions.—Length of the tubes 2.0 to 3.0, breadth 0.03 to 0.06; branches 0.1 to 0.3.

Habitat.—Central Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms.

Genus 670. Aulodendron,^[288] n. gen.

Definition.—Aulacanthida with a veil of tangential needles, and with radial tubes, which bear numerous, irregularly scattered, lateral and terminal branches.

The genus Aulodendron differs from the other Aulacanthida in the possession of lateral and terminal branches, which are irregularly scattered on the radial tubes and not arranged in regular verticils. The branches are usually short, simple or forked, rarely longer and again irregularly ramified.

1. Aulodendron antarcticum, n. sp. (Pl. 105, fig. 5).

Radial tubes cylindrical, more or less curved, in the inner proximal half smooth and half as broad as in the outer distal half, which is studded with irregularly curved, partly branched spines, arising usually perpendicularly from the tube. The majority of the spines usually simple, the minority forked, with two to four short branches, the largest spines scarcely twice as long as the breadth of the tube.

Dimensions.—Length of the tubes 0.7 to 0.9, breadth 0.01 to 0.02; length of the branches 0.02 to 0.04.

Habitat.—Antarctic Ocean (Kerguelen), Stations 156 to 159, surface.

2. Aulodendron pacificum, n. sp. (Pl. 105, fig. 2).

Radial tubes cylindrical, slightly curved, in the proximal half smooth, in the distal half with scattered lateral branches, which are partly simple, partly forked, about twice as long as the breadth of the tube, and bear at the distal end a spathilla with five to six recurved teeth. The distal end of the tubes bears a spherical knob, which is separated by a deep stricture and armed with a bunch of six to twelve strong conical teeth.

Dimensions.—Length of the tubes 1 to 1.2, breadth 0.015 to 0.02; branches 0.03 to 0.04.

Habitat.—South Pacific, Station 293, depth 2025 fathoms.

3. Aulodendron australe, n. sp. (Pl. 105, fig. 3).

Radial tubes cylindrical, straight, thin, smooth in the proximal half, armed with numerous lateral branches in the distal half; the majority of the branches forked, about as long as the breadth of the tube, with two or three short ramules, each of which bears a spinulate terminal knob. The distal end of the tubes also forked, with two or three divergent branches.

Dimensions.—Length of the tubes 1.2 to 1.6, breadth 0.01 to 0.012.

Habitat.—South Pacific, Station 289; New Zealand, Station 169, surface.

4. Aulodendron atlanticum, n. sp.

Radial tubes cylindrical, tapering gradually towards the two ends; smooth and straight in the proximal half, irregularly curved and branched in the distal half, with ten to twenty (rarely more) branches, which arise almost perpendicularly from the tube. The proximal branches are from four to eight times as long as the greatest breadth of the tube, forked, with two or three short ramules; the distal branches are much smaller and simple. The distal end of each branch bears a spathilla with four to six short teeth.

Dimensions.—Length of the tubes 2.4 to 3.6, breadth 0.06 to 0.08.

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

5. Aulodendron indicum, n. sp. (Pl. 105, fig. 1).

Radial tubes cylindrical, irregularly curved, tapering gradually towards the two ends; smooth in the proximal half, irregularly branched in the distal half, with ten to twenty or more curved branches. The proximal branches are very large, one-sixth to one-fourth as long as the tube and irregularly ramified; the distal branches are much shorter, also ramified or simple. All the branches are more or less curved and bear a spinulate knob at the distal end.

Dimensions.—Length of the tubes 1.2 to 1.8, breadth 0.02 to 0.03; length of the branches 0.1 to 0.3.

Habitat.—Indian Ocean; Cocos Islands (Rabbe), surface.

Order II. PHÆOSPHÆRIA, Haeckel, 1879.

Definition.—Phæodaria with a simple or double, usually spherical lattice-shell, which is not bivalved and has no peculiar mouth or peristome. Central capsule placed in the centre of the shell.

Family LXXIV. Orosphærida, n. fam. (Pls. 106, 107).

Definition.—Phæodaria with a big spherical (sometimes polyhedral or ellipsoidal), very coarse shell, which is composed of thick bars containing an axial canal. Nodal points of the coarse network without astral septa. Meshes of moderate size, irregularly polygonal. Surface of the shell usually with radial spines and pyramidal elevations. No peculiar mouth in the shell. Central capsule tripylean, in the centre of the shell.

The family Orosphærida comprises those Phæodaria which possess a simple spherical or polyhedral lattice-shell, composed of hollow, very thick, non-articulate rods, without a peculiar shell-mouth. They agree in the considerable size of the spherical lattice-shell and the absence of a peculiar shell-mouth with the other Phæosphæria, but differ from them in the coarse and irregular shape of the massive network, which is composed of irregular polygonal meshes, separated by very thick concentrically stratified rods, containing a fine axial canal. The closely allied Sagosphærida differ from them in the delicate shape of the solid and very thin, filiform rods of the network, and its subregular triangular meshes. The Aulosphærida differ in the development of the peculiar nodal cavities and astral septa, by which the thin-walled cylindrical tubes of the articulated network are separated in the stellate nodal points. The Cannosphærida, closely allied to these latter, also differ in the articulated network, and further in the possession of an internal concentric shell. The Castanellida are sometimes similar to the Orosphærida, but distinguished by a peculiar large shell-mouth and a network of different shape.

The Orosphærida belong to the biggest Radiolaria, and the lattice-work of their spherical shell is of a ruder and coarser shape than in any of the other families of this class. Nevertheless they have been hitherto perfectly unknown, and were first discovered by the Challenger. We have been able to distinguish in the collection four genera and twenty-seven species. This strange fact may be explained by the circumstance, that they are in general rare, and restricted to a few localities, and that probably all the species are inhabitants of great depths. Complete shells also are rarely found, whilst broken fragments of their big shells, easily recognisable by the coarse irregular meshes and the thick stratified bars, are met with frequently in the Radiolarian ooze of some Pacific Stations, especially at Stations 265 and 268, at a depth of 2900 fathoms.

The lattice-shell of the Orosphærida is usually spherical, or an endospherical polyhedron (Pl. 106, fig. 4); rarely one axis is somewhat prolonged, so that the shell becomes slightly ellipsoidal (Pl. 106, fig. 1). Its diameter is usually between 2 and 3, often also between 2 and 1 mm., rarely more than 3, or less than 1 mm. The largest shells observed attained 5 to 6, the smallest 0.5 to 0.6 mm. Their general habit is very characteristic, so that they may be easily distinguished from all other spherical lattice-shells, especially from the Castanellida and from the simple Monosphærida (Cenosphæra, Acanthosphæra), with which I confounded them in the beginning (hence the first shell observed, figured in 1878, was placed among the Monosphærida in Pl. 12). A closer examination of the coarse network and of the peculiar structure of its thick bars always enables one to recognise even small isolated fragments of broken shells.

The meshes of the coarse network exhibit in all observed Orosphærida a very irregular form and unequal size; the majority are usually more or less quadrangular, more rarely they are triangular, pentagonal or hexagonal, very rarely rounded. They are often arranged in parallel rows, which seem to be determined by prominent crests, connecting the bases of the radial spines (Pl. 12, fig. 1; Pl. 106, fig. 4, &c.). The diameter of the meshes is usually between 0.05 and 0.1, often 0.1 to 0.2, rarely more than 0.25, or less than 0.025 mm. In Oroplegma, which develops an outer loose, spongy shell around the inner primary shell, the big meshes of the former become much larger and very irregular (Pl. 107, fig. 1).

The coarse bars which separate the large meshes of the irregular network are very thick and massive, cylindrical, usually of unequal thickness, straight or slightly curved, never angular or prismatic. Their diameter is usually between 0.01 and 0.02, rarely more than 0.03 or less than 0.005 mm. Their surface is either smooth or slightly spinulate. Examined in the dry state and by strong lenses, they constantly exhibit a fine, but distinct longitudinal striation, as the expression of concentric stratification. A fine axial canal or central tubule is usually visible in the axis of each rod, and often this axial canal is studded with numerous short lateral branches (Pl. 107, figs. 2, 4, 8). But very often the axial canals become rudimentary or lost, or are developed only in a part of the bars (Pl. 12, fig. 1). When they are completely developed, the entire network of the shell is drained by a reticulate system of communicating axial canals; they are probably filled by jelly in the living body. This tubular system never attains that regularity and high development which is constantly found in the Aulosphærida; and the characteristic stellate nodal points of the latter, with their astral septa, are never found in any of the Orosphærida. Moreover the wall of the tubular bars is very thin and structureless in the Aulosphærida, very thick and stratified in the Orosphærida, the enclosed canal very wide in the former, very narrow in the latter. The stratification of the concentric cylindrical lamellæ, which surround the narrow axial canal, is effected by the gradual deposition of the concentric layers, and is very similar to that which is found in the thick spicula of many sponges. The peculiar structure of the bars in the Orosphærida becomes very distinct if the skeleton be burned, or acted upon by fire for some time; it then assumes a brown colour and its surface often appears dimpled. Sometimes the concave dimples on the surface of the bars are rather deep and separated by prominent crests (Pl. 107, figs. 4, 7). The few genera of Orosphærida which are here distinguished have all the same structure, are closely allied, and differ mainly in the shape of the outer surface of the lattice-sphere. The latter is quite simple and smooth only in Orona. In the common Orosphæra (Pl. 106, figs. 1-3) it is studded with radial spines. In the most frequent form, Oroscena, the shell has a pyramidal or tent-shaped elevation on the base of each radial spine, and usually the bases of the neighbouring spines are connected by strong prominent crests, the edges of the three-sided or four-sided pyramids (Pl. 12, fig. 1; Pl. 106, fig. 4). This remarkable form is more or less polyhedral, with concave sides, and is similar to the characteristic shells which are represented by Auloscena among the Aulosphærida, by Sagoscena and Sagoplegma among the Sagosphærida (compare Pls. 108 and 110). The pyramids or tents, however, are in these latter more regularly and distinctly developed than in the Orosphærida. The radial spines which arise form the top of the pyramids are often branched, and the branches become connected to form an outer enveloping secondary shell or a loose spongy framework in Oroplegma (Pl. 107, fig. 1).

The radial spines of the Orosphærida never exhibit a constant number or disposition in the individual species; their usual number is from twenty to sixty. Their form exhibits two different types, which, however, are not sharply separated; robust club-shaped and slender rod-shaped spines. The robust club-shaped spines are usually about as long as the diameter of the shell; they are longitudinally striped in the basal part, spinulate or reticulately dimpled in the distal part; sometimes they are straight, at other times curved or undulate (Pl. 106, figs. 1-4; Pl. 107, figs. 4-6). The slender rod-shaped spines are usually longer than the diameter of the shell, cylindrical, more or less curved or even undulate, smooth or thorny, sometimes irregularly branched, and often the branches are all or partly connected (Pl. 106, fig. 3; Pl. 107, fig. 1). In the majority of the shells observed the radial spines were found to be partly broken off. Their structure is the same as that of the bars of the network; but the central axial canal and the surrounding concentric lamellæ are usually more distinct than in the latter.

The central capsule of the Orosphærida lies in the centre of the spherical lattice-shell, surrounded by the voluminous calymma, which fills up its cavity. The form, structure, and size of the central capsule are the same as in the closely allied Aulosphærida (Pl. 111, fig. 2). Its diameter is usually about 0.2, or between 0.15 and 0.25, rarely more than 0.3 or less than 0.12. The dark phæodium is of about the same volume as the central capsule, and envelops its oral half with the radiate operculum and the proboscis of the astropyle. The two opposite parapylæ are small.