6. Dendrocircus barbadensis, n. sp.

Gate irregularly ovate or nearly semicircular. Ring of the same oblique form, thick, with interrupted and distorted edges, armed with eight to twelve larger irregularly formed and branched acute spines; between them numerous conical smaller spines. This common species is very polymorphous and variable.

Dimensions.—Diameter of the ring 0.05 to 0.08; length of the spines 0.005 to 0.02.

Habitat.—Fossil in Barbados.

7. Dendrocircus stalactites, n. sp. (Pl. 81, fig. 14).

Gate obliquely ovate. Ring irregularly ovate or roundish, very thick, without edges, armed with numerous (eight to twelve or more) short and stout branches, which are shorter than the diameter of the gate, irregularly disposed and branched, with very numerous clustered blunt ramules.

Dimensions.—Diameter of the gate 0.07 to 0.09; length of the spines 0.02 to 0.06.

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

Subfamily 2. Cortinida, Haeckel.

Definition.—Stephanida with typical basal feet (or cortinar feet).

Genus 405. Cortina,^[24] n. gen.

Definition.—Stephanida with a simple dipleuric or bilateral ring, bearing at the base three divergent feet (one odd caudal and two paired lateral feet).

The genus Cortina and the following Stephanium represent together the small but very important group of Cortinida, differing from the simple Lithocircida in the possession of three typical basal feet, which are transmitted to the majority of the Nassellaria by heredity, and produce their peculiar triradial structure. They appear therefore as a combination of the simple ring (Zygocircus) with three basal feet (Plagonium). One of these three divergent feet is the odd caudal foot, opposite to the apical horn; the two others are the paired lateral or pectoral feet. (On the probable origin and the typical signification of Cortina compare above, pp. 891-894.)

1. Cortina tripus, n. sp. (Pl. 83, fig. 9).

Ring ovate, smooth, or with a few short thorns. Apical horn oblique, curved, simple, smooth, about as long as the sagittal axis of the ring. Feet divergent, curved, simple, smooth, about as long as the horn; the caudal foot shorter than the two pectoral feet. Very variable in form and size.

Dimensions.—Height of the ring 0.06 to 0.09, breadth 0.04 to 0.06; length of the feet 0.05 to 0.1.

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

2. Cortina typus, n. sp. (Pl. 97, fig. 1).

Ring kidney-shaped or nearly semicircular, with revolute vertical dorsal rod and strongly curved ventral rod; both rods with two pairs of spine-bunches. Apical horn nearly straight, thorny, longer than the ring, directed a little obliquely backwards. Feet slightly curved, of equal length, two to three times as long as the ring; each armed with few large bunches of curved spines, which are more developed in the caudal foot than in the two pectoral feet.

Dimensions.—Height of the ring 0.14, breadth 0.08; length of the feet 0.2 to 0.3.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

3. Cortina conifera, n. sp.

Ring subcircular, smooth. Apical horn and the three divergent feet of equal size and similar form, cylindrical, straight, about as long as the ring, at the distal end thickened, with a dimply cone (similar to Tripospyris conifera and Tripospyris eucolpa, Pl. 84, figs. 4, 7).

Dimensions.—Height of the ring 0.08, breadth 0.06; length of the feet 0.09.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

4. Cortina furcata, n. sp.

Ring elliptical, with three forked horizontal spines (one on the dorsal and two on the ventral rod). Apical horn and the three divergent feet of equal size, somewhat longer than the ring, slightly curved, in the distal half forked.

Dimensions.—Height of the ring 0.07, breadth 0.05; length of the feet 0.09.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms. Fossil in Barbados.

5. Cortina dendroides, n. sp.

Ring ovate, with six pairs of branched horizontal spines, three on the dorsal and three on the ventral rod. Apical horn very large, arborescent, about as long and as broad as the ring. Feet similar to the horn, also richly branched, of equal size. All the rods and their branches curved, with prominent distorted edges.

Dimensions.—Height of the ring 0.13 to 0.17, breadth 0.1 to 0.12; length of the feet 0.15 to 0.2.

Habitat.—Central Pacific, Stations 266 to 274, depth 2350 to 2925 fathoms.

6. Cortina cervina, n. sp. (Pl. 92, fig. 21).

Ring ovate, with four pairs of forked horizontal spines (two dorsal and two ventral pairs). Apical horn straight and stout, as long as the ring, with trifid point. Three feet equal, widely divergent, very large, branched like a deer's antler, with very numerous short and stout, curved and pointed branches. All rods and branches roundish, without edges.

Dimensions.—Height of the ring 0.1, breadth 0.07; length of the feet 0.12 to 0.16.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

Genus 406. Stephanium,^[25] n. gen.

Definition.—Stephanida with a simple dipleuric or bilateral ring, bearing at the base four divergent feet (two sagittal and two lateral feet).

The genus Stephanium differs from the preceding nearly allied Cortina in the production of four basal feet; the new foot, missing in the latter, is the anterior or sternal foot. Therefore Stephanium may be regarded as the archetype of all those Nassellaria in which, on the base of the sagittal ring, there are developed four typical feet—two sagittal feet (the posterior caudal and anterior sternal foot) and two lateral feet (right and left). On the origin of Stephanium compare above, p. 893, &c.

1. Stephanium quadrupes, n. sp. (Pl. 92, fig. 20).

Ring ovate, with three prominent dentate edges and a short pyramidal apical horn. Four feet all of nearly equal size, about as long as the ring, also with three thorny edges, in the upper half divergent, in the lower convergent.

Dimensions.—Height of the ring 0.12, breadth 0.08; length of the feet 0.11 to 0.13.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Stephanium tetrapus, n. sp.

Ring elliptical, without edges, thorny, with a stout, thorny apical horn of the same length. Four feet curved and irregularly branched, divergent, of different size. The two sagittal feet (the anterior sternal and posterior caudal) about as long as the ring. The two lateral feet (right and left) nearly twice as long, more richly branched.

Dimensions.—Height of the ring 0.16, breadth 0.11; length of the feet 0.15 to 0.3.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms. Fossil in Barbados.

Family XLIX. Semantida, n. fam.

Definition.—Stephoidea with a single vertical ring (the primary sagittal ring), bearing on its base a horizontal ring (basal or cortinar ring) with two to four or more basal gates (or cortinar pores).

The family Semantida differs from the preceding Stephanida in the development of a small horizontal ring on the base of the primary vertical sagittal ring. By the crossing of these two rings a small latticed basal plate is formed, with one or two pairs of pores; rarely with a greater number of "basal pores." The production of this characteristic "basal plate" is of the greatest morphological importance, as the beginning of the numerous different lattice-formations, which are differentiated in the great majority of Nassellaria.

In my Prodromus (1881, p. 446) I had enumerated the Semantida with three genera (Nos. 298 to 300) as a separate subfamily of the Dyostephida or "Stephoidea biannularia," and characterised these "Dyostephanida" by the following definition: "Skeleto annulis duobus composito, qui in duobus planis invicem perpendicularibus jacent; altero annulo (sagittali) verticali, altero (basali) horizontali." As the names there given were already employed with another signification, and as the Zygostephanida (there united with the Dyostephanida) are more closely related to the Coronida, I now change the names, and propose to call the family Semantida, expressing by this term the typical similarity of the skeleton to a signet-ring (Semantis, Semantrum, Semantidium).

At about the same time, some Stephoidea of this family were accurately described by Bütschli (1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 495, Taf. xxxii. figs. 6, 7, 8). He called them Stephanolithis, a name which Ehrenberg had employed, not for complete shells of Radiolaria, but for isolated parts of such, and for siliceous fragments of different skeletons, needles of Sponges, &c. The three species described by Bütschli represent three different genera of our Semantida, viz., Semantis spinescens (with two gates in the basal plate), Semantrum mülleri (with four gates), and Semantidium haeckelii (with six gates). He pointed out the great morphological value of the fenestrated basal plate and its paired gates, as beginnings of numerous other Nassellaria. But his opinion, that in all Spyroidea and Cyrtoidea, derived from these, two pairs of basal gates were constant, was erroneous, nor was the formation of the first pair naturally explained; he supposed that the formation of the basal plate begins by development of an odd sagittal apophysis, arising from the base of the primary sagittal ring. But this odd sagittal apophysis ("der unpaare mediane Kieselfortsatz c1", loc. cit., p. 497) is in reality not a primary and essential part of the skeleton, but secondary and of little morphological value, absent in the majority of the Semantida and of the other Nassellaria.

We divide our family Semantida into two different subfamilies, which possibly possess a direct phylogenetic relation to the two subfamilies of Stephanida:—The Semantiscida have no typical feet, and have arisen directly from the Lithocircida; the Cortiniscida, however, possess the three typical basal feet of Cortina, and may therefore be derived directly from the Cortinida. Since these three cortinar feet are probably identical with the three primary radial rods of the Plectoidea, an immediate affinity also to these Nassellaria is indicated.

The Semantiscida, which do not possess these three basal cortinar feet, are the simpler forms of the family. The simplest of all, and perhaps the common ancestral form of the whole family, is Semantis (Pl. 92, figs. 1, 2). It may be derived from Archicircus or Zygocircus by development of two pairs of horizontal apophyses on its base, around the porochora of the central capsule. The two rods of each side (right and left), becoming curved one towards the other, and meeting laterally, form a simple horizontal gate, and the two paired basal gates together, a horizontal ring or basal ring, to which the primary sagittal ring is perpendicular. In the next allied genus, Semantrum (Pl. 92, figs. 3-5), three pairs of horizontal apophyses are developed, and therefore two pairs of basal gates produced, an anterior and a posterior. In the third genus, Semantidium (Pl. 92, figs. 6, 7), three pairs of basal pores or gates are visible, surrounded and separated by four pairs of horizontal apophyses, which arise from the base of the sagittal ring. Finally, in Clathrocircus (Pl. 92, figs. 8-10) the number of apophyses is much increased, and two parallel rows of pores are developed along the two sides of the sagittal ring.

The basal plate or the "seal," developed from the base of the primary sagittal ring or "signet-ring," is therefore a horizontal ring, which becomes bisected by the latter, and exhibits either one pair of primary "basal gates" or two or three pairs of these important basal pores, rarely more. Since these pores possess the greatest morphological value, and are probably everywhere homologous, we give to them and to the separating apophyses certain names, and call the anterior pair of gates, "jugular pores" (i in our figures, the pair I of Bütschli); the middle (usually the largest) pair, "cardinal pores" (k in our figures, the pair II of Bütschli), and the posterior, smaller pair, "cervical pores," l. The typical pairs of rods, by the union of which these basal pores arise, are the following:—(1) the clavicular or furcular rods, f, the first pair (rods e1 of Bütschli), (2) the coracal rods, e, between the jugular and cardinal pores (rods e of Bütschli), (3) the scapular rods, g, between the cardinal and cervical pores (rods e2 of Bütschli), (4) the cervical rods, the fourth pair of apophyses, the most posterior, h. Bütschli supposes that the topographical succession of the three typical pairs of basal pores is also the chronological succession, the jugular being formed first, the cardinal second and the cervical pores third but it seems that this succession is often altered and that the cardinal pores (the largest), appear first, the jugular pores (in front of them) second and the cervical pores third (or perhaps sometimes in the inverse succession).

The Cortiniscida, the second subfamily of Semantida, differ from the preceding Semantiscida in the possession of three typical basal feet, which are probably inherited from the Cortinida, and perhaps indirectly from the Plagonida (Plagoniscus). The simplest and the most important form of this second family is Cortiniscus (Pl. 92, figs. 11-13), differing from its probable ancestral form, Cortina, in the development of a basal ring, produced by horizontal union of the basal apophyses. The three typical feet are the same as in all triradiate Nassellaria, two paired pectoral feet (p₁, p₁₁) diverging on the anterior base of the sagittal ring, whilst the odd caudal foot (c) lies on its posterior base in the sagittal plane and appears as a basal prolongation of the dorsal rod of the sagittal ring; the upper part of the dorsal rod is usually prolonged into an ascending apical horn. In Stephaniscus (Pl. 92, figs. 14, 15) four basal feet are visible, an anterior or sternal foot (z) being added as a prolongation of the basal rod of the ring, opposite to the caudal foot. Finally, Semantiscus (Pl. 92, figs. 16-18) is distinguished by the possession of six divergent basal feet, probably identical with those of all six-radiate Nassellaria; three of these may be regarded as primary and perradial, the odd caudal and the paired pectoral feet; the three other intercalated as secondary or interradial feet, the odd sternal (z) and the paired tergal feet (t₁, t₁₁).

The basal plate of these Cortiniscida exhibits the same important differences as in the preceding Semantiscida, either one, or two, or three pairs of basal gates being developed. But there occur also in some species (mainly in Cortiniscus) only three basal gates, an odd anterior (between the two pectoral feet and a connecting horizontal bar), and two paired posterior (between the two pectoral and the odd caudal foot). It requires further accurate researches to solve the important problem, what the true homologies of these typical basal pores and the separating bars are in the different genera of Semantida. In Semantiscus there are three pairs of basal pores in the horizontal seal, corresponding to those of Semantidium and the radial rods or bars between, these are the basal parts of the six radial feet; therefore the odd caudal foot (t) seems to be the posterior, and the odd sternal foot (z) the anterior prolongation of the basal part of the primary sagittal ring; the two paired anterior or pectoral feet (p₁, p₁₁) the prolongations of the coracal rods (e) and the two paired posterior or tergal feet (t₁, t₁₁), the prolongations of the scapular rods (g). But it is not yet certain whether these six radial feet and the separating gates of the basal plate are all the same and truly homologous in all six-radiate Nassellaria. In every case the comparative study of the Semantida is of the highest value for the accurate knowledge of the Monopylea.

Synopsis of the Genera of Semantida.

Subfamily 1. Semantiscida, Haeckel.

Definition.—Semantida without typical basal feet or cortinar feet.

Genus 407. Semantis,^[26] n. gen.

Definition.—Semantida with two basal pores (or jugular pores), without typical basal feet.

The genus Semantis, the most primitive and the oldest of the Semantida, is of the greatest morphological interest, as the first form of Stephoidea which produces gates or pores by communicating branches, and therefore the probable ancestral form not only of this family, but of the greater number of all Stephoidea, and perhaps even of all Spyroidea and Cyrtoidea. Semantis arises from Archicircus by the production of two pairs of lateral branches from the basilar rod of the sagittal ring, one anterior pair of clavicular rods, and one posterior pair of coracal rods. By junction of the clavicular and coracal rod on each side arises a left and a right pore, the "jugular pore or jugular gate."

1. Semantis biforis, n. sp. (Pl. 92, fig. 2).

Sagittal ring obliquely ovate, nearly trapezoidal, with six pairs of short mammillated knobs or branches; dorsal rod straight, vertical, with two pairs of knobs, ventral rod strongly convex, also with two pairs of knobs; two other pairs in the apical rod. Basilar rod horizontal, straight. Basal ring with six pairs of similar knobs, three on each side. Basal gates ovate or nearly triangular.

Dimensions.—Height of the sagittal ring 0.09, breadth 0.07.

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

2. Semantis distoma, n. sp.

Sagittal and basal ring nearly of the same form as in the preceding species, but half as thick and armed with numerous branched spines which are about half as long as the diameter of the main gate, and with thin and curved pointed branches.

Dimensions.—Height of the sagittal ring 0.11, breadth 0.08.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

3. Semantis dipyla, n. sp.

Sagittal ring kidney-shaped, very thick, with six pairs of short, thorny, or irregularly tuberculated knobs (two dorsal, two apical, and two ventral pairs). Basal ring smooth, scarcely half as thick, horizontal, with two semicircular basal gates, about half as broad as the main gate. From the two opposite lateral corners of the basal ring two slender upwardly curved spines arise, resembling the basal part of a commencing frontal ring.

Dimensions.—Height of the sagittal ring 0.08, breadth 0.05.

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

4. Semantis sigillum, n. sp. (Pl. 92, fig. 1).

Sagittal ring elliptical, with four pairs of stout arborescent spines (two apical and two equatorial pairs), which are irregularly branched and forked, with numerous thin lateral branches. Apex with a short conical trifid vertical horn. Basal ring thorny, with obliquely descending slightly curved bars.

Dimensions.—Height of the sagittal ring 0.12, breadth 0.09.

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

5. Semantis distephanus, n. sp. (Pl. 83, fig. 3).

Sagittal ring thin, semicircular, smaller than the thin basal ring, which exhibits two semicircular gates. Both rings are armed with numerous small spines of equal size, which on the former are arranged in two, on the latter in three regular rows. (The basal rod of the sagittal ring, separating the two basal gates, in fig. 3 is, by mistake, not distinctly enough drawn.)

Dimensions.—Height of the sagittal ring 0.06, breadth 0.08.

Habitat.—Tropical Atlantic, Station 348, surface.

6. Semantis spinescens, Haeckel.

Sagittal ring ovate with four pairs of thin, irregularly branched spines, two apical pairs, one on the straight dorsal rod and one on the curved ventral rod. Basilar rod with a posterior and an anterior forked rod (commencing caudal and sternal foot). Basal ring square, with two lateral spines, and two triangular gates scarcely one-third as broad as the ring-gate. An internal ascending procolumna (rod c₁ in the figure of Bütschli) connects the basal and ventral rods of the sagittal ring.

Dimensions.—Height of the sagittal ring 0.1, breadth 0.07.

Habitat.—Fossil in Barbados.

Genus 408. Semantrum,^[27] n. gen.

Definition.—Semantida with four basal pores (two anterior jugular and two posterior cardinal pores), without typical basal feet.

The genus Semantrum, one of the most important of the Nassellaria, arises from the preceding Semantis by duplication of the two basal gates. Behind the pair of coracal rods there arises from the basilar rod of the sagittal ring a third pair of lateral horizontal branches, the scapular rods. These become connected with the coracal rods on each side, and so produce a second posterior pair of basal pores, the "cardinal gates." These are constantly larger than the anterior "jugular gates." Therefore the vertical ring of Semantrum possesses a horizontal basal ring with four very characteristic gates, enclosed by three pairs of lateral curved and connected branches, and these become transmitted by heredity to the majority of the Nassellaria.

1. Semantrum quadrifore, n. sp. (Pl. 92, fig. 5).

Sagittal ring subcircular or ovate, with three edges and four sagittal forked spines on the odd edge (two dorsal and two ventral spines). Basal ring decagonal, with ten simple or forked spines on the ten corners. Jugular gates tetragonal. Cardinal gates pentagonal.

Dimensions.—Height of the sagittal ring 0.09, breadth 0.07.

Habitat.—Tropical Atlantic, Station 351, surface.

2. Semantrum tetrastoma, n. sp. (Pl. 92, fig. 3).

Sagittal ring semicircular, thorny, without edges. Basal ring tetragonal or nearly cordate, with a small anterior and a large posterior bow-shaped incision; on the lateral edges with numerous irregular thorns. Jugular gates pear-shaped. Cardinal gates nearly kidney-shaped.

Dimensions.—Height of the sagittal ring 0.1 to 0.14, breadth 0.07 to 0.09.

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

3. Semantrum tetrapylum, n. sp.

Sagittal ring elliptical, tuberculate. Basal ring trapezoidal, also with roundish thick rods and small irregular tubercles on the margin. Jugular gates ovate, two-thirds as broad as the triangular cardinal gates.

Dimensions.—Height of the sagittal ring 0.08, breadth 0.05.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

4. Semantrum mülleri, Haeckel.

Sagittal ring nearly semicircular or obliquely ovate, thorny. Basal ring also nearly semicircular, with two slight sagittal incisions (one anterior and one posterior), on the lateral edges with numerous small thorns. Jugular pores (pair I of Bütschli) pear-shaped. Cardinal pores (pair II of Bütschli) triangular. Sometimes (but not constantly) a pair of cervical bows connects the scapular bars with the subvertical dorsal rod of the sagittal ring.

Dimensions.—Height of the sagittal ring 0.09, breadth 0.06.

Habitat.—Fossil in Barbados.

5. Semantrum sphragisma, n. sp.

Sagittal ring circular, smooth. Basal ring also nearly circular and smooth; its four basal gates of nearly equal size, elliptical or subcircular; the jugular pores scarcely smaller than the cardinal pores. All rods smooth, cylindrical, without edges and thorns.

Dimensions.—Height of the sagittal ring 0.08, breadth 0.07.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms; also fossil in Barbados.

6. Semantrum bütschlii, n. sp.

Sagittal ring triangular, with vertical straight ascending dorsal rod, horizontal straight basilar rod and obliquely ascending, slightly curved ventral rod; all rods nearly cylindrical, with irregular branched thorns and distorted edges. Jugular pores triangular, scarcely half as broad as the large semicircular cardinal pores.

Dimensions.—Height of the sagittal ring 0.11, breadth 0.08.

Habitat.—Fossil in Barbados.

7. Semantrum signarium, n. sp. (Pl. 92, fig. 4).

Sagittal ring obliquely ovate, thorny. Basal ring kidney-shaped or nearly pentagonal, with broad concave dorsal incision and five larger branched spines on the five corners; between them smaller thorns. Jugular gates pear-shaped, scarcely half as broad as the triangular cardinal gates.

Dimensions.—Height of the sagittal ring 0.12, breadth 0.09.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Genus 409. Semantidium,^[28] n. gen.

Definition.—Semantida with six basal pores (two anterior jugular, two middle cardinal, and two posterior cervical pores), without typical basal feet.

The genus Semantidium exhibits a further developmental stage of the basal plate of the Semantida. Whilst this plate in Semantis possesses one pair of basal pores, and in Semantrum two pairs, here in Semantidium it has three pairs. The new third pair is produced on the dorsal edge of the basal plate, which becomes connected with the basal part of the dorsal rod of the sagittal ring by a pair of cervical rods. The middle pair of pores (the cardinal) are always larger than the anterior (jugular) and the posterior (cervical pores). The same form of basal plate is preserved in numerous Spyroidea and Cyrtoidea, as a "cortinar septum with six collar pores," (e.g., Pl. 53, fig. 18).

1. Semantidium hexastoma, n. sp. (Pl. 92, fig. 6).

Sagittal ring ovate, thorny. Basal ring rhombic or nearly square, with four short conical descending spines on the four prominent edges (two sagittal and two lateral); between them numerous smaller irregular thorns. Jugular and cervical gates nearly equal, ovate, half as broad as the triangular cardinal gates between them.

Dimensions.—Height of the sagittal ring 0.14, breadth 0.1.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Semantidium sexangulum, n. sp.

Sagittal ring ovate, with six pairs of short branched thorns (two apical, two dorsal, and two ventral). Basal ring hexagonal, with three pairs of short branched thorns on the six corners (one sagittal pair, one posterior and one anterior). All six gates of the basal plate triangular, the jugular and cervical a little smaller than the cardinal gates.

Dimensions.—Height of the sagittal ring 0.1, breadth 0.07.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

3. Semantidium haeckelii, Bütschli.

Sagittal ring elliptical, with three pairs of short horizontal branched spines, one apical and two equatorial pairs (one dorsal and one ventral). Basal ring roundish hexagonal, with numerous short thorns on the margin. Jugular pores ovate, about half as broad as the ovate cardinal pores and twice as broad as the small cervical pores.

Dimensions.—Height of the sagittal ring 0.08, breadth 0.06.

Habitat.—Fossil in Barbados.

4. Semantidium signatorium, n. sp. (Pl. 92, fig. 7).

Sagittal ring semicircular, thorny; basal ring pentagonal, with short spines on the margin and five stronger thorny spines on the five corners. Jugular pores ovate, smaller than the triangular cervical pores. Cardinal pores two to three times as large as each of the former, pentagonal.

Dimensions.—Height of the sagittal ring 0.08, breadth 0.12.

Habitat.—North Pacific, Station 341, depth 2300 fathoms.

Genus 410. Clathrocircus,^[29] Haeckel, 1881, Prodromus, p. 447.

Definition.—Semantida with a variable number of pores on the apical and the basal part of the ring, symmetrically arranged, without typical basal feet.

The genus Clathrocircus comprises those Semantida in which the sagittal ring bears not only basal pores (as in the three preceding genera) but also apical pores (on the opposite pole of the main axis), or a variable number of pores along the whole ring. All these pores are symmetrically arranged in pairs. In the simplest form there are only two apical pores opposite to four basal pores, whilst in the highest state of development the whole ring bears two complete circles of pores. At both poles of the transverse axis two large lateral gates remain open. If these become closed by lattice-work, Clathrocircus passes over into Dictyospyris.

1. Clathrocircus hexaporus, n. sp.

Sagittal ring circular, smooth, with three pairs of pores (one apical and two basal). The two apical pores are triangular with two lateral spines, and correspond to the two mitral gates of the Tympanida. The four basal pores form a hexagonal basal plate, with six lateral spines, and correspond to the four basal pores of Semantrum; the two jugular are pear-shaped, and half as broad as the two triangular cardinal pores.

Dimensions.—Height of the sagittal ring 0.08, breadth 0.06.

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

2. Clathrocircus octoporus, n. sp.

Sagittal ring elliptical, smooth, with four pairs of pores (two apical and two basal). The four apical pores are of nearly equal size, subcircular, and form a regular cross around the apical pole. The four basal pores are ovate, and form a quadrangular plate, armed with marginal thorns; the two jugular pores are somewhat smaller than the two cardinal pores.

Dimensions.—Height of the sagittal ring 0.11, breadth 0.08.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

3. Clathrocircus decaporus, n. sp.

Sagittal ring ovate, thorny, with five pairs of pores (two apical and three basal). The four apical pores are roundish and form a cross. The six basal pores are triangular and form a hexagonal plate with thorny margin; the two jugular pores are somewhat larger than the two cervical, and half as broad as the two cardinal pores.

Dimensions.—Height of the sagittal ring 0.09, breadth 0.07.

Habitat.—North Pacific, Station 256, depth 2950 fathoms.

4. Clathrocircus stapedius, n. sp. (Pl. 92, fig. 8).

Sagittal ring ovate, smooth, with six pairs of pores (two apical and four basal). The four apical pores are of nearly equal size and form a quadrangular mitral plate with two large lateral horns. The eight basal pores are of very different size (the four central far larger than the two anterior and the two posterior), and form a hexagonal basal plate, also with two large lateral horns. The four branched lateral horns (two upper and two lower) form together an incomplete frontal ring.

Dimensions.—Height of the sagittal ring 0.1, breadth 0.08.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.