5. Clathrocircus dictyospyris, n. sp. (Pl. 92, fig. 9).
Sagittal ring ovate, thorny, with eight pairs of pores. The four apical and the four basal pores are elliptical and far larger than the four dorsal and the four ventral pores. Resembles a Dictyospyris with open lateral gates.
Dimensions.—Height of the sagittal ring 0.08, breadth 0.06.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
6. Clathrocircus multiforis, n. sp. (Pl. 92, fig. 10).
Sagittal ring circular, smooth, with ten to twelve pairs of roundish pores, forming together a complete lattice-girdle with two parallel circular rows of pores. Four larger of these are the four gates of the basal ring (two jugular and two cardinal pores).
Dimensions.—Diameter of the ring 0.1 to 0.15, breadth 0.03 to 0.05.
Habitat.—Central Pacific, Stations 263 to 274, depth 2350 to 2925 fathoms.
Definition.—Semantida with large, typical, regularly disposed basal feet (originally three cortinar feet, one odd caudal and two paired pectoral).
Definition.—Semantida with three typical basal feet (an odd caudal foot and two paired lateral or pectoral feet).
The genus Cortiniscus is of peculiar importance, as the common ancestral form of the Cortiniscida, or those Semantida in which the basal ring is provided with typical, regularly disposed basal feet—three, four, or six. Since these typical basal feet (or "cortinar feet") are preserved in the greater number of all Nassellaria, determining their triradial structure, they possess a great morphological value. Cortiniscus exhibits the same three primary feet as Cortina, from which it differs in the production of two or more basal pores (between the odd caudal and the paired lateral feet).
1. Cortiniscus tripodiscus, n. sp. (Pl. 92, fig. 11).
Sagittal ring ovate, thorny, with three prominent, distorted edges; its dorsal rod nearly straight and vertical, with one or two pairs of short thorns; its ventral rod strongly curved, with three or four pairs of divergent thorns. Basal ring larger than the sagittal ring, with two semicircular gates and obliquely ascending halves, which on the inner and lower edge are smooth, on the outer and upper thorny. Apical horn and the three divergent feet nearly equal, straight, about as long as the sagittal ring, with three thorny edges.
Dimensions.—Height of the sagittal ring 0.1 to 0.12, breadth 0.07 to 0.09.
Habitat.—Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.
2. Cortiniscus dipylaris, n. sp. (Pl. 92, fig. 13).
Sagittal ring nearly semicircular, with prominent distorted edges and six pairs of small roundish papillate tubercles (three pairs on the straight dorsal, three on the curved ventral rod). Apical horn short and stout, with a tuberculate knob. Basal ring smaller than the sagittal ring with two elliptical gates. Three feet short and stout, irregularly branched like a cauliflower, with numerous short papillate tubercles.
Dimensions.—Height of the sagittal ring 0.11, breadth 0.08.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
3. Cortiniscus tripylaris, n. sp.
Sagittal ring elliptical, smooth. Apical horn conical, smooth. Basal ring larger than the sagittal ring, with three elliptical gates of equal size; two paired, posterior (jugular pores) between the basal parts of the caudal foot and the two pectoral feet, and an odd, anterior (sternal pore) between the basal parts of the two pectoral feet and a connecting horizontal convex sternal bow.
Dimensions.—Height of the sagittal ring 0.09, breadth 0.06.
Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.
4. Cortiniscus tetrapylaris, n. sp.
Sagittal ring elliptical, with four pairs of short branched thorns, two posterior on the straight dorsal, and two anterior on the curved ventral rod. Basal ring smaller than the sagittal ring, with four triangular gates; the two anterior (jugular pores) a little smaller than the two posterior (cardinal pores). Apical horn and the three divergent feet shorter than the sagittal ring, irregularly branched, with curved, often tuberculate branches.
Dimensions.—Height of the sagittal ring 0.08 to 0.12, breadth 0.06 to 0.1.
Habitat.—Fossil in Barbados.
5. Cortiniscus typicus, n. sp. (Pl. 92, fig. 12).
Sagittal ring ovate, thorny, with three distorted edges; dorsal rod nearly straight and vertical prolonged upwards into a stout thorny apical horn, downwards into the caudal foot. Basal ring smaller than the sagittal ring, with four elliptical or nearly triangular gates; the two anterior (jugular pores) about half as large as the two posterior (cardinal pores). Three feet of equal size, thorny, divergent, straight or slightly curved, about as long as the diameter of the sagittal ring.
Dimensions.—Height of the sagittal ring 0.14 to 0.18, breadth 0.1 to 0.12.
Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, at various depths.
Definition.—Semantida with four typical basal feet (two sagittal and two lateral or pectoral feet).
The genus Stephaniscus differs from the preceding Cortiniscus in the production of a fourth (sternal) foot, and therefore exhibits the same relation to it that Stephanium among the Stephanida bears to Cortina. It differs from Stephanium, in the production of a basal ring, with pores or gates between the bases of the basal feet. Two of these feet are sagittal (the posterior caudal and the anterior sternal foot), whilst the other two are lateral or pectoral (right and left). The basal lattice-plate exhibits either two pores ("jugular gates") or four pores (two anterior jugular and two posterior cardinal gates).
1. Stephaniscus tetrapodius, n. sp.
Sagittal ring nearly circular, smooth, with a short conical apical horn. Basal ring square, smooth, with two triangular gates. Four feet simple, equal, conical, divergent, about as long as the diameter of the ring.
Dimensions.—Height of the sagittal ring 0.08, breadth 0.07.
Habitat.—Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.
2. Stephaniscus quadrifurcus, n. sp. (Pl. 92, fig. 14).
Sagittal ring subcircular, thorny with a small thorny apical horn. Basal ring also nearly circular, with two large semicircular gates and a few small thorns. All four feet curved and forked, the fork-branches again ramified, with numerous short curved and pointed branches. The two lateral feet (right and left) are larger and more branched than the two sagittal feet (sternal and caudal foot).
Dimensions.—Height of the sagittal ring 0.12, breadth 0.1.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
3. Stephaniscus quadrigatus, n. sp. (Pl. 92, fig. 15).
Sagittal ring oblique, ovate, with three prominent thorny edges; its dorsal rod nearly straight and vertical, the ventral rod strongly curved; apex with a small curved horn. Basal ring with a few short thorns and four gates of different size; the two anterior (jugular pores) ovate or nearly triangular, two-thirds as broad as the two posterior subcircular or pentagonal (cardinal pores). All four feet simple, curved, with three edges, the posterior (caudal) foot larger, the anterior (sternal) foot smaller than the two lateral (pectoral) feet.
Dimensions.—Height of the sagittal ring 0.09, breadth 0.07.
Habitat.—Tropical Atlantic, Station 351, surface.
4. Stephaniscus medusinus, n. sp.
Sagittal ring elliptical, thorny, with a larger apical horn. Basal ring nearly square, with short marginal thorns and four large ovate gates of nearly equal size. All four feet of equal size divergent, curved, irregularly branched, with short curved branches.
Dimensions.—Height of the sagittal ring 0.13, breadth 0.09.
Habitat.—South Atlantic, Station 332, depth 2200 fathoms. Fossil in Barbados.
Definition.—Semantida with six typical basal feet (two sagittal, two pectoral, and two tergal feet).
The genus Semantiscus may be the archetype of those Nassellaria which exhibit six typical basal feet, in combination with the sagittal ring. Three of these are the primary feet of Cortina and Cortiniscus, the other three are secondary productions between the former. The basal ring may possess either two, four, or six basal pores.
1. Semantiscus hexapodius, n. sp. (Pl. 92, fig. 16).
Sagittal ring elliptical, with a large branched apical horn. Basal ring small, square, with two small triangular gates (or jugular pores). From its periphery there arise six short and stout cylindrical feet, one very large (caudal) from the posterior corner, two tergal on each side, two opposite (pectoral) from the lateral corners, and one odd sternal from the anterior corner. All six spines bear a bunch of ten to twenty stout pointed conical branches, partly simple, partly forked.
Dimensions.—Height of the sagittal ring 0.12, breadth 0.08.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
2. Semantiscus hexaspyris, n. sp. (Pl. 92, fig. 18).
Sagittal ring semicircular, broad, latticed, with two pairs of irregular dorsal and two pairs of ventral pores. The dorsal rod is straight and vertical, prolonged upwards into a short serrate apical horn, downwards into a straight linear caudal foot. The ventral rod is curved and prolonged into a similar sternal foot. Basal ring hexagonal, with four ovate gates (two smaller jugular and two larger cardinal pores); its four lateral corners prolonged into four curved thorny lateral feet (two anterior larger pectoral, and two posterior smaller tergal feet). This species may be regarded as a commencing Hexaspyris or Liriospyris.
Dimensions.—Height of the sagittal ring 0.08, breadth 0.06.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
3. Semantiscus hexapylus, n. sp. (Pl. 92, fig. 17).
Sagittal ring ovate, thorny, with a small apical horn. Basal ring with six roundish or nearly triangular gates; the two jugular pores are smaller than the two cardinal and larger than the two cervical pores. The separating bars between these six pores are prolonged into six straight, thorny widely divergent feet; three larger feet (the caudal and the two pectoral) with a pair of apophyses, three smaller between them simple (the sternal and the two tergal feet).
Dimensions.—Height of the sagittal ring 0.13, breadth 0.09.
Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.
Triostephida, Haeckel, 1881, Prodromus, p. 445.
Definition.—Stephoidea with two crossed vertical rings, perpendicular one to the other (the primary sagittal and the secondary frontal ring). Usually their common base bears a horizontal basal ring, but a mitral ring (or a horizontal ring at the apex) is never developed.
The family Coronida comprises those Stephoidea in which the primary sagittal ring (of the Stephanida and Semantida) becomes crossed by a second vertical ring, the lateral or frontal ring. Between these two vertical meridian rings, perpendicular to one another, four large apertures remain constantly open, the "lateral" gates. But besides these four constant openings, usually (excepting only in the Zygostephanida) other gates are developed on the common base of the two crossed rings, produced by a third, horizontal, basal ring. These basal gates are the same which we have found already in the Semantida.
The distinction of the Coronida from the other Stephoidea is always easy. In the Stephanida and Semantida, the frontal ring, or the second meridian ring, which we find in all Coronida, is never developed. On the other hand these latter never exhibit the typical "mitral ring," or the second, upper, horizontal ring, which distinguishes the Tympanida.
We distinguish here, among the Coronida, four different subfamilies, which perhaps afterwards may be better separated as families. Of these four groups the Zygostephanida and Acanthodesmida exhibit the nearest relationship to the Stephanida, whilst the Eucoronida and Trissocyclida possess a closer affinity with the Semantida.
The Zygostephanida, constituting the first subfamily, exhibit four large gates only, and differ from all other Coronida in the absence of a basal ring and of basal gates. Therefore the skeleton is entirely composed of two crossed vertical rings, perpendicular to one another; the first is the primary or sagittal ring (inherited from the Stephanida), the second is the new lateral or frontal ring. The four large lateral gates are either quite simple (Zygostephanus) or partly closed by loose and irregular lattice-work (Zygostephanium). The Zygostephanida may be derived directly from the Stephanida by development of lateral branches forming a frontal ring. They commonly possess the same characteristic spines or branches, and the same typical difference between the straight dorsal rod and convex ventral rod of the sagittal ring, which we found in the greater number of Stephanida. The frontal ring is commonly elliptical or kidney-shaped, and much larger than the ovate sagittal ring.
The Acanthodesmida, forming the second subfamily of Coronida, differ from all other members of this family in the possession of a large simple basal gate, surrounded by a simple horizontal basal ring. Only this ring is complete, whilst the two crossed vertical meridian rings (the primary sagittal and the secondary frontal ring) are incomplete, both truncated at the base by the basal ring. Therefore there remain here between the three rings five large gates (recognised previously by Johannes Müller in 1856 in Acanthodesmia): four lateral gates (the same as in the Zygostephanida) and one central basal gate. The latter is always quite simple and serves for the emission of the pseudopodia, arising from the basal pole of the central capsule. The four lateral gates are either quite simple (Coronidium) or partly closed by irregular loose lattice-work (Acanthodesmia). The subfamily Acanthodesmida may be derived either directly from the Stephanida (by development of a central basal gate) or from the Eucoronida (by loss of the basilar part of the sagittal ring).
The Eucoronida, the third subfamily, are the most important group of the Coronida; their numerous species are much more frequent and more widely distributed than those of the other three subfamilies. They may be derived immediately from the Semantida by the development of a lateral or frontal ring. This remains incomplete in the basal part, whilst the two other rings, perpendicular to it (the vertical sagittal ring and the horizontal basal ring), are complete. Therefore the shell constantly exhibits six large open gates between the three rings; four lateral gates (the same as in the Zygostephanida and Acanthodesmida) and two basal gates (inherited from Semantis); the latter correspond to the "jugular pores" of the Spyroidea and Cyrtoidea; they remain constantly simple. The four lateral gates may also remain simple (Eucoronis) or they may become partly closed by irregular loose lattice-work (Plectocoronis). The remarkable genus Podocoronis is distinguished by the development of typical descending basal feet, which are regularly disposed and correspond to the typical "cortinar feet" of the other Nassellaria. There may be developed either two lateral feet (as lower prolongations of the segments of the frontal ring), or three feet (one caudal and two pectoral, as in Cortina and Cortiniscus), or four feet (two sagittal and two lateral, as in Stephanium and Stephaniscus), or six feet (two sagittal, two pectoral, two tergal, as in Semantiscus), sometimes numerous feet (as in Petalospyris and Anthocyrtis, &c.).
The Trissocyclida represent the fourth and last subfamily of Coronida, distinguished from all others in the possession of three complete rings, perpendicular one to another, and of eight large gates separated by them. Two of the three rings are vertical (the primary sagittal and the secondary frontal ring), the third is horizontal (the basal ring). The four upper gates correspond to the four lateral gates of the preceding three subfamilies; the four lower gates are the same as the four basal gates of Semantrum (two primary jugular and two secondary cardinal gates); therefore the Trissocyclida may be derived directly from these Semantida by development of a complete frontal ring. Probably the two jugular gates were originally smaller than the two cardinal, but usually they have become equal. In Tristephanium (the common ancestral form of the Trissocyclida) and in the closely allied Tricyclidium the four basal gates remain smaller than the four lateral gates. But in two other genera, Trissocircus and Trissocyclus, the four lower or basal gates reach the same size as the four upper or lateral gates; therefore all eight gates become equal and the basal ring becomes equatorial. In the most regular species of the latter genera also the three rings become perfectly equal and cannot be any longer distinguished. Here the original bilateral (or dipleuric) fundamental form of the shell passes over into a regular cubic or octahedral form (with three equal, isopolar axes, perpendicular one to another). The eight large gates of the Trissocyclida usually remain simple (Tristephanium, Trissocircus), but sometimes they become partly closed by loose lattice-work (Tricyclidium, Trissocyclus).
The original rings, and the secondary rods or bars, composing the loose framework of the Coronida are either roundish (with circular or elliptical transverse section) or three-edged (with triangular transverse section), rarely quadrangular or provided with distorted edges. The branches or spines arising from them, are either simple or branched, and offer a great variety in number, form, and disposition. The most important forms are those which develop the three typical basal feet of Cortina, e.g., Podocoronis cortina (Pl. 97, fig. 2).
The Central Capsule of the Coronida is the same as in the other Stephoidea (comp. p. 937), and offers all those characteristic peculiarities of "Monopylea" which we have mentioned above in the general description of the Nassellaria (p. 890). Usually it is spherical or ellipsoidal, often violin-shaped or bilobed, with a sagittal constriction. The porochora of its basal pole is in close contact with the base of the sagittal ring.
|
I. Subfamily Zygostephanida. Four lateral gates (no basal gate). |
brace | Two meridional rings (sagittal and frontal) complete, perpendicular to one another (no basal ring). | brace | Four lateral gates simple, | 414. Zygostephanus. | ||
| Four lateral gates partly latticed, | 415. Zygostephanium. | ||||||
|
II. Subfamily Acanthodesmida. Five large gates (four lateral and one simple basal). |
brace | Two meridional rings (sagittal and frontal) incomplete, both truncated by the complete horizontal basal ring. | brace | Four lateral gates simple, | 416. Coronidium. | ||
| Four lateral gates partly latticed, | 417. Acanthodesmia. | ||||||
|
III. Subfamily Eucoronida. Six large gates (four lateral and two basal). |
brace | Two rings (the sagittal meridional ring and the horizontal basal ring) complete, the frontal meridian ring incomplete. | brace | Basal ring without larger descending feet. | brace | Gates simple, | 418. Eucoronis. |
| Gates partly latticed, | 419. Plectocoronis. | ||||||
| Basal ring with large, regularly disposed, descending feet. Gates simple, | 420. Podocoronis. | ||||||
|
IV. Subfamily Trissocyclida. Eight large gates (four upper lateral and four lower basal). |
brace | Two meridional rings (sagittal and frontal) and the horizontal basal ring complete. All three complete rings perpendicular to one another. | brace | Four upper gates larger than the four lower. | brace | Gates simple, | 421. Tristephanium. |
| Gates partly latticed, | 422. Tricyclidium. | ||||||
| All eight gates of equal size. | brace | Gates simple, | 423. Trissocircus. | ||||
| Gates partly latticed, | 424. Trissocyclus. | ||||||
| I. Subfamily Zygostephanida. Four lateral gates (no basal gate). | ||||||||
| Two meridional rings (sagittal and frontal) complete, perpendicular to one another (no basal ring). | ||||||||
| Four lateral gates simple, | ||||||||
| 414. Zygostephanus. | ||||||||
| Four lateral gates partly latticed, | ||||||||
| 415. Zygostephanium. | ||||||||
| II. Subfamily Acanthodesmida. Five large gates (four lateral and one simple basal). | ||||||||
| Two meridional rings (sagittal and frontal) incomplete, both truncated by the complete horizontal basal ring. | ||||||||
| Four lateral gates simple, | ||||||||
| 416. Coronidium. | ||||||||
| Four lateral gates partly latticed, | ||||||||
| 417. Acanthodesmia. | ||||||||
| III. Subfamily Eucoronida. Six large gates (four lateral and two basal). | ||||||||
| Two rings (the sagittal meridional ring and the horizontal basal ring) complete, the frontal meridian ring incomplete. | ||||||||
| Basal ring without larger descending feet. | ||||||||
| Gates simple, | ||||||||
| 418. Eucoronis. | ||||||||
| Gates partly latticed, | ||||||||
| 419. Plectocoronis. | ||||||||
| Basal ring with large, regularly disposed, descending feet. Gates simple, | ||||||||
| 420. Podocoronis. | ||||||||
| IV. Subfamily Trissocyclida. Eight large gates (four upper lateral and four lower basal). | ||||||||
| Two meridional rings (sagittal and frontal) and the horizontal basal ring complete. All three complete rings perpendicular to one another. | ||||||||
| Four upper gates larger than the four lower. | ||||||||
| Gates simple, | ||||||||
| 421. Tristephanium. | ||||||||
| Gates partly latticed, | ||||||||
| 422. Tricyclidium. | ||||||||
| All eight gates of equal size. | ||||||||
| Gates simple, | ||||||||
| 423. Trissocircus. | ||||||||
| Gates partly latticed, | ||||||||
| 424. Trissocyclus. | ||||||||
Definition.—Coronida with four large lateral gates, without basal gate. Skeleton composed of two complete vertical rings, perpendicular one to another—the primary sagittal and the secondary frontal ring.
Definition.—Coronida with four large, simple, lateral gates, without basal gate and lattice-work. Skeleton composed of two simple meridional rings, perpendicular to one another.
The genus Zygostephanus, founded by me in 1862 for the Mediterranean Zygostephanus mülleri, is the simplest and most primitive of all the Coronida, and may therefore be regarded as the common ancestral form of this family. The simple skeleton is composed of two meridional rings only, perpendicular one to another—a sagittal and a frontal ring.
Definition.—The two vertical rings of nearly equal height, therefore without sagittal constriction.
1. Zygostephanus dissocircus, n. sp. (Pl. 93, fig. 1).
Both rings elliptical, of nearly equal height, smooth, without spines. Frontal ring somewhat longer than the sagittal. No sagittal constriction.
Dimensions.—Height of the rings 0.07, breadth 0.1.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
2. Zygostephanus serratus, n. sp.
Both rings elliptical, of nearly equal height, with a serrate prominent edge on the outer convexity (in the transverse section three-edged). No sagittal constriction.
Dimensions.—Height of the rings 0.08, breadth 0.12.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
3. Zygostephanus mülleri, Haeckel.
Zygostephanus mülleri, Haeckel, 1862, Monogr. d. Radiol., p. 268, Taf. xii. fig. 2.
Both rings elliptical, of nearly equal height, armed with numerous (about fifty) slender curved spines, as long as the radius of the rings; commonly each ring with twelve pairs of divergent spines. No sagittal constriction.
Dimensions.—Height of the rings 0.06, breadth 0.1.
Habitat.—Mediterranean (Messina), surface.
4. Zygostephanus ramosus, n. sp.
Both rings elliptical, of nearly equal height, armed with numerous branched spines, which are arranged on each ring in two divergent rows; the branches of the spines are curved and partly protect the open gates. No sagittal constriction.
Dimensions.—Height of the rings 0.07, breadth 0.09.
Habitat.—North Pacific, Station 244, depth 2900 fathoms.
Definition.—The two vertical rings of different heights; the frontal ring higher than the sagittal ring, therefore with a sagittal constriction in the median plane.
5. Zygostephanus reniformis, n. sp.
Frontal ring kidney-shaped, in the upper half convex, in the lower concave, in the latter with a deep sagittal constriction, armed with numerous irregular short spines. Sagittal ring thicker and lower, only two-thirds as high, with four pairs of short divergent spines (two ventral and two dorsal pairs).
Dimensions.—Height of the frontal ring 0.13, breadth 0.2.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
6. Zygostephanus violina, n. sp.
Frontal ring violin-shaped, on the upper and the lower margin concave, with a deep sagittal constriction, armed with numerous irregular spines, which are partly simple, partly branched. Sagittal ring thicker and lower, only half as high, with a few short conical spines at the apical and basal poles.
Dimensions.—Height of the frontal ring 0.12, breadth 0.18.
Habitat.—South Atlantic, Station 332, depth 2200 fathoms.
7. Zygostephanus bicornis, n. sp. (Pl. 93, fig. 2).
Frontal ring violin-shaped, on the upper and the lower margin concave, with a deep sagittal constriction; its two halves pentagonal. Between numerous smaller spines there arise from the frontal ring six groups of larger branched spines, two odd in the corners of the highest points (curved like two horns), two branched pairs on the prominent lateral corners (at right and left), and two pairs in the corners of the lowest points (like four branched basal feet). Sagittal ring only two-thirds as high, with four pairs of irregular spines.
Dimensions.—Height of the frontal ring 0.11, breadth 0.16.
Habitat.—South Pacific Station 300, depth 1375 fathoms.
Definition.—Coronida with four large, partly latticed, lateral gates, without basal gate. Skeleton composed of two meridional rings perpendicular to each other.
The genus Zygostephanium differs from the preceding ancestral genus Zygostephanus in the development of lattice-work along the two crossed rings, produced by their anastomosing branches. Therefore the four large lateral gates between them, which are quite simple, in the preceding genus here become more or less fenestrated.
1. Zygostephanium dizonium, n. sp. (Pl. 93, fig. 3).
Tympaniscus dizonius, Haeckel, 1882, Manuscript.
Both rings elliptical, of nearly equal height, smooth, without spines. Sagittal ring with four pairs of small pores (two apical pairs and two basal pairs). Frontal ring with three pairs of small pores (one pair lateral, one pair above and one pair below).
Dimensions.—Height of the frontal ring 0.08, breadth 0.12.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
2. Zygostephanium paradictyum, n. sp. (Pl. 93, fig. 4).
Frontal ring kidney-shaped, in the upper half convex, in the lower concave, in the latter with a deep sagittal constriction. Sagittal ring ovate, about two-thirds as high as the frontal ring. Both rings three-edged, armed with numerous short and branched bristle-shaped spines, which anastomose along their three edges and produce two series of irregular polygonal pores.
Dimensions.—Height of the frontal ring 0.08, breadth 0.13.
Habitat.—North Pacific, Station 236, surface.
3. Zygostephanium constrictum, n. sp.
Frontal ring violin-shaped, concave on the upper and lower margins, with a deep sagittal constriction. Sagittal ring ovate, about two-thirds as high as the frontal ring. Both rings covered with numerous branched irregular spines, which partly anastomose along the edges of the rings, and produce small irregular polygonal pores.
Dimensions.—Height of the frontal ring 0.12, breadth 0.18.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
Definition.—Coronida with five large gates (four lateral and one basal). Skeleton composed of three rings, perpendicular one to another, two of which are vertical and incomplete (the primary or lateral, and the secondary or frontal), the third is horizontal and complete (the tertiary or basal ring).
Definition.—Coronida with five large simple gates (four lateral and one basal). Skeleton composed of two incomplete meridional rings and one complete basal ring, without lattice-work.