Chapter IV: Front Matter (4)

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 (_p__{1}, _p__{11}) 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 (_t__{1}, _t__{11}).

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 (_p__{1}, _p__{11}) the prolongations of the coracal rods (_e_) and the two paired posterior or tergal feet (_t__{1}, _t__{11}), 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.

{956}_Synopsis of the Genera of Semantida._

-------------------------------------------------------------------------
I. Subfamily Semantiscida.
Basal ring without typical, regularly disposed basal feet
(no cortinar feet).
-------------------------------------------------------------------------
{ Two basal pores, 407. _Semantis_.
Only two, four, or six {
basal pores (no dorsal { Four basal pores, 408. _Semantrum_.
and ventral pores). {
{ Six basal pores, 409. _Semantidium_.

Besides four basal pores, also apical pores or
dorsal and ventral pores along the whole ring, 410. _Clathrocircus_.
-------------------------------------------------------------------------
II. Subfamily Cortiniscida.
Basal ring with typical, regularly disposed basal feet
(cortinar feet).
-------------------------------------------------------------------------
{ One odd caudal foot and
Three basal feet. { two paired lateral
{ feet, 411. _Cortiniscus_.

{ Two sagittal and two
Four basal feet. { lateral or pectoral
{ feet, 412. _Stephaniscus_.

{ Two sagittal, two
Six basal feet. { pectoral, and two
{ tergal feet, 413. _Semantiscus_.

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 {957}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.

{958}6. _Semantis spinescens_, Haeckel.

_Stephanolithis spinescens_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p.160, Taf. i. fig. 29.

_Stephanolithis spinescens_, Bütschli, 1882, Zeitschr. f. wiss. Zool.,
vol. xxxvi. p. 497, Taf. xxxii. figs. 7_a_, 7_b_.

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 _c__1 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.

{959}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.

_Stephanolithis mülleri_, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi pp. 499, 539, Taf. xxxii. figs. 8_a_, 8_b_, 8_c_.

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 {960}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 {961}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.

Stephanolithis Haeckelii, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi. pp. 499, 538, Taf. xxxii. figs. 6_a_, 6_b_.

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_.

{962}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.

{963}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.

Subfamily 2. CORTINISCIDA, Haeckel.

_Definition._--#Semantida# with large, typical, regularly disposed basal feet (originally three cortinar feet, one odd caudal and two paired pectoral).

Genus 411. _Cortiniscus_,[30] n. gen.

_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, {964}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.

{965}Genus 412. _Stephaniscus_,[31] n. gen.

_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 {966}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.

Genus 413. _Semantiscus_,[32] n. gen.

_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 {967}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.

Family #L. CORONIDA#, Haeckel.

_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.

{968}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 {969}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.

{970}_Synopsis of the Genera of Coronida._

-------------------------------------------------------------------------
I. Subfamily Zygostephanida. Four lateral gates (no basal gate).
-------------------------------------------------------------------------
Two meridional rings }Four lateral gates
(sagittal and frontal) } simple, 414. _Zygostephanus_.
complete, perpendicular }
to one }Four lateral gates
another (no basal } partly latticed, 415. _Zygostephanium_.
ring).
-------------------------------------------------------------------------
II. Subfamily Acanthodesmida.
Five large gates (four lateral and one simple basal).
-------------------------------------------------------------------------
Two meridional rings }Four lateral gates
(sagittal and frontal) } simple, 416. _Coronidium_.
incomplete, both }
truncated by the }Four lateral gates
complete horizontal } partly latticed, 417. _Acanthodesmia_.
basal ring.
-------------------------------------------------------------------------
III. Subfamily Eucoronida. Six large gates (four lateral and two basal).
-------------------------------------------------------------------------
Two rings (the {Basal ring {Gates simple, 418. _Eucoronis_.
sagittal meridional{ without larger{
ring and the { descending {Gates partly
horizontal basal { feet. { latticed, 419. _Plectocoronis_.
ring) complete, the{
frontal meridian {Basal ring with large,
ring incomplete. { regularly disposed,
{ descending feet. Gates
{ simple, 420. _Podocoronis_.
-------------------------------------------------------------------------
IV. Subfamily Trissocyclida.
Eight large gates (four upper lateral and four lower basal).
-------------------------------------------------------------------------
Two meridional {Four upper {Gates simple, 421. _Tristephanium_.
rings (sagittal and{ gates larger {
frontal) and the { than the {Gates partly
horizontal basal { four lower. { latticed, 422. _Tricyclidium_.
ring complete. All {
three complete {All eight gates{Gates simple, 423. _Trissocircus_.
rings perpendicular{ of equal size.{
to one another. { {Gates partly
{latticed, 424. _Trissocyclus_.

Subfamily 1. ZYGOSTEPHANIDA, Haeckel, 1881, Prodromus, p. 446.

_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.

Genus 414. _Zygostephanus_,[33] Haeckel, 1862, Monogr. d. Radiol., p. 268.

_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 {971}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.

Subgenus 1. _Zygostephus_, Haeckel, 1881, Prodromus, p. 446.

_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.

{972}Subgenus 2. _Zygostephaniscus_, Haeckel, 1881, Prodromus, p. 446.

_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.

Genus 415. _Zygostephanium_,[34] Haeckel, 1881, Prodromus, p. 446.

_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.

{973}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.

Subfamily 2. ACANTHODESMIDA, Haeckel, 1881, Prodromus, p. 445.

_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).

Genus 416. _Coronidium_,[35] Haeckel, 1881, Prodromus, p. 445.

_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.

{974}The genus _Coronidium_ and the following, nearly allied _Acanthodesmia_, form together the peculiar subfamily of Acanthodesmida--not in the wider sense in which I first founded this group (1862, Monogr. d. Radiol., p. 265), but in the restricted sense, which is exactly defined in my Prodromus (1881, p. 445). According to this definition, the shell is composed of three different rings, perpendicular to one another; only one of these is complete, the simple horizontal basal ring; the two others are incomplete and vertical (the primary or sagittal and the secondary or frontal ring). Therefore there remain constantly between the three rings five characteristic large openings or gates; four of these are lateral (between the halves of the two meridional rings), the fifth is basal, enclosed by the horizontal basal ring. The longest known type of this subfamily is _Acanthodesmia vinculata_, the five characteristic gates of which are clearly distinguished by its discoverer, Johannes Müller ("Das Gehäuse besteht nur aus den Leisten zwischen fünf grossen Lücken"). The Acanthodesmida may be derived from the Eucoronida by reduction of the basilar rod of the sagittal ring. If in _Eucoronis_ this basal rod be lost, _Coronidium_ arises.

1. _Coronidium dyostephanus_, n. sp. (Pl. 82, fig. 7).

Frontal ring elliptical, with few scattered thorns, twice as broad as high, and three times as broad as the smooth rhombic basal ring. Sagittal ring semicircular, very stout, twice as thick as the two other rings, with short lateral thorns (in the figure seen from the apical pole, which exhibits a four-lobed dimple). Basal gate rhombic.

_Dimensions._--Height of the frontal ring 0.08, breadth 0.16.

_Habitat._--Central Pacific, Station 263, depth 2650 fathoms.

2. _Coronidium diadema_, n. sp. (Pl. 82, fig. 8).

Frontal ring kidney-shaped, one and a half times as broad as high, with a slight sagittal constriction. Sagittal ring ovate, smaller, about of the same size as the elliptical basal ring. Rods of all three rings cylindrical, bearing numerous short and stout curved spines, partly simple, partly branched. Four bunches of larger spines on the four corners of the basal ring, and one very large bunch on the apical pole. Basal gate elliptical, one and a half times as broad as long.

_Dimensions._--Height of the frontal ring 0.13, breadth 0.18.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

3. _Coronidium cervicorne_, n. sp. (Pl. 82, fig. 1).

Frontal ring kidney-shaped, twice as broad as high, one and a half times as broad as the elliptical basal ring, both with a slight sagittal constriction. Sagittal ring ovate. All three rings {975}(in the figure seen from the apical pole) with cylindrical rods, armed with numerous stout spines, branched like a deer's antler. Basal gate rather oblong, twice as broad as long.

_Dimensions._--Height of the frontal ring 0.08, breadth 0.16.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

4. _Coronidium acacia_, n. sp. (Pl. 82, fig. 2).

Frontal ring and sagittal ring nearly circular, of equal size, truncated at the base. Basal ring circular, somewhat smaller. All three rings with prominent edges, bearing bunches of short and straight pointed spines, like those of an Acacia. Basal gate circular.

_Dimensions._--Height of the frontal ring 0.12, breadth 0.14.

_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms.

Genus 417. _Acanthodesmia_,[36] J. Müller, 1856, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 485.

_Definition._--#Coronida# with five large, partly latticed gates (four lateral and one basal). Skeleton composed of two incomplete, partly fenestrated meridional rings, and one complete basal ring.

The genus _Acanthodesmia_, the oldest known form of all Coronida, differs from the preceding _Coronidium_, its ancestral form, in the development of irregular loose lattice-work along the rings, and therefore bears to it the same relation that _Zygostephanium_ does to _Zygostephanus_. The first species described by Johannes Müller, _Acanthodesmia vinculata_ ("with five large gates between the bars of the shell") remains the true type of this genus; the second species described by him (_Acanthodesmia dumetum_) belongs to the Plectanida (_Polyplecta_).

1. _Acanthodesmia vinculata_, J. Müller.

_Acanthodesmia vinculata_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 30, Taf. i. figs. 4-6 (_non_ 7).

_Lithocircus vinculatus_, J. Müller, 1856, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 484.

Frontal ring violin-shaped, one and a half times as broad as high, with a sagittal constriction. Sagittal ring ovate, smaller. The four gates between the two rings are partly fenestrated by a few thin threads, irregularly branched and connecting the two rings. A few short thorns are scattered here and there. Basal gate elliptical.

_Dimensions._--Height of the frontal ring 0.12, breadth 0.18.

_Habitat._--Mediterranean (Nice), Atlantic (Canary Islands), surface.

{976}2. _Acanthodesmia ceratospyris_, n. sp.

Frontal ring violin-shaped, one and a half times as broad as high, with a deep sagittal constriction. Sagittal ring semicircular, half as high as the frontal ring. The four gates between the two rings are partly fenestrated by anastomosing branches of the numerous, irregularly branched spines, which cover all three rings. Basal gate nearly circular, smaller than the sagittal ring.

_Dimensions._--Height of the frontal ring 0.08, breadth 0.12.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

3. _Acanthodesmia corona_, n. sp. (Pl. 93, fig. 5).

Frontal ring kidney-shaped, nearly twice as broad as high, with a flat sagittal constriction. Sagittal ring semicircular. The four gates between the two rings are partly fenestrated by an arachnoidal network, composed of thin, irregularly branched threads, arising from the rings. The edges of all three rings are armed with irregular thorns. Basal gate circular, larger than the sagittal ring.

_Dimensions._--Height of the frontal ring 0.08, breadth 0.14.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

4. _Acanthodesmia mülleri_, n. sp.

Frontal ring kidney-shaped with a deep sagittal constriction. Sagittal ring ovate. The four gates between the two rings irregularly fenestrated, with a few large polygonal meshes. Edges of the rings with a few scattered thorns. Basal gate violin-shaped.

_Dimensions._--Height of the frontal ring 0.1, breadth 0.16.

_Habitat._--Tropical Atlantic, Station 347, surface.

Subfamily 3. EUCORONIDA, Haeckel, 1881, Prodromus, p. 445.

_Definition._--#Coronida# with six large gates (four lateral and two basal gates). Skeleton composed of three rings perpendicular to one another, two of which are complete (the vertical sagittal, and the horizontal basal ring); the third is incomplete (the vertical frontal ring).

Genus 418. _Eucoronis_,[37] Haeckel, 1881, Prodromus, p. 445.

_Definition._--#Coronida# with six large simple gates (four lateral and two basal). Skeleton composed of two complete rings (the sagittal and basal) and one incomplete (frontal) ring. Basal ring without typical feet.

{977}The genus _Eucoronis_ and the following two nearly allied genera (_Plectocoronis_ and _Podocoronis_) compose together the important subfamily Eucoronida. In this typical main group of Coronida the shell is constantly composed of three rings and six gates. The vertical sagittal ring and the horizontal basal ring are complete (as in the Semantida); the vertical frontal ring is incomplete. Between these three rings remain six large open gates, the four upper (or lateral) are always much larger than the four lower (or basal gates). _Eucoronis_ may be derived from _Semantis_ by development of the frontal ring.

Subgenus 1. _Acrocoronis_, Haeckel, 1881, Prodromus, p. 445.

_Definition._--Rings smooth or rough, armed with numerous short spines or thorns.

1. _Eucoronis perspicillum_, n. sp. (Pl. 82, fig. 6).

Frontal ring elliptical, twice as broad as high, with a slight constriction at the apical pole, armed with three pairs of short conical spines, one apical pair (near the constriction) and two lateral pairs (one upper and one lower pair). Sagittal ring of the same height, half the breadth and double the thickness, also armed with three pairs of spines (one basal, one dorsal, and one ventral pair).

_Dimensions._--Height of the frontal ring 0.11, breadth 0.22.

_Habitat._--Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms.

2. _Eucoronis lævigata_, n. sp.

Frontal ring elliptical, smooth, one and a half times as broad as high, without sagittal constriction, with horizontal basal gates. Sagittal ring of the same height and thickness, also elliptical and smooth. No spines on either of the smooth rings.

_Dimensions._--Height of the frontal ring 0.1, breadth 0.15.

_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.

3. _Eucoronis nephrospyris_, n. sp. (Pl. 82, fig. 5).

Frontal ring kidney-shaped, in the upper half convex, in the lower concave, with a sagittal constriction (often much deeper than in the specimen figured). Sagittal ring ovate, about two-thirds as high as the frontal ring. Rods of both rings without edges, cylindrical, armed with numerous short conical thorns.

_Dimensions._--Height of the frontal ring 0.1 to 0.12, breadth 0.15 to 0.18.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, many Stations, surface and at various depths.

{978}4. _Eucoronis angulata_, n. sp. (Pl. 82, fig. 3).

Frontal ring violin-shaped, twice as broad as high, on the upper and the lower margin concave, with a deep sagittal constriction. Sagittal ring pentagonal, with straight horizontal basal rod, two-thirds as high as the frontal ring. Rods of both rings with sharp prominent edges, bearing numerous short pyramidal spines.

_Dimensions._--Height of the frontal ring 0.09, breadth 0.17.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

Subgenus 2. _Lithocoronis_, Haeckel, 1881, Prodromus, p. 445.

_Definition._--Rings armed with numerous large, branched or arborescent spines.

5. _Eucoronis cervicornis_, n. sp.

Frontal ring kidney-shaped, in the upper half convex, in the lower concave, with sagittal constriction. Sagittal ring ovate, two-thirds as high as the frontal ring. Both rings armed with numerous stout spines, irregularly branched like a deer's antler. (Very similar to _Coronidium cervicorne_, Pl. 82, fig. 1, which I formerly confounded with it, but differing in the complete sagittal ring, which in the latter form is incomplete and has lost its basal part.)

_Dimensions._--Height of the frontal ring 0.12, breadth 0.2.

_Habitat._--Central Pacific, Station 264, surface.

6. _Eucoronis arborescens_, n. sp.

Frontal ring kidney-shaped, with a deep sagittal constriction in the concave basal part. Sagittal ring ovate, half as high as the frontal ring. Both rings armed with numerous thin, richly branched and arborescent spines (branches much thinner and more numerous than in the preceding and following species).

_Dimensions._--Height of the frontal ring 0.15, breadth 0.25.

_Habitat._--Equatorial Atlantic, Station 247, surface.

7. _Eucoronis challengeri_, n. sp. (Pl. 82, fig. 4).

_Lithocoronis challengeri_, Haeckel, 1881, Prodromus, p. 445.

Frontal ring violin-shaped, one and a half times as broad as high, with a strong sagittal constriction. Sagittal ring nearly circular, two-thirds as high as the frontal ring. Both rings armed with numerous irregularly branched spines. (The specimen figured, with red central capsule and numerous xanthellæ, was observed living by me at the Canary Islands.)

_Dimensions._--Height of the frontal ring 0.1 to 0.12, breadth 0.14 to 0.17.

_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, surface and at various depths.

{979}Genus 419. _Plectocoronis_,[38] Haeckel, 1881, Prodromus, p. 445.

_Definition._--#Coronida# with six large, partly latticed gates (four lateral and two basal). Skeleton composed of two complete rings (the sagittal and basal) and one incomplete (frontal) ring. Basal ring without developed typical feet.

The genus _Plectocoronis_ differs from the preceding _Eucoronis_, its ancestral form, in the development of loose irregular lattice-work along the two meridional rings, and therefore bears to it the same relation that _Acanthodesmia_ does to _Coronidium_. If the lattice-work become more complete and close the gates, these Coronida pass over directly into #Spyroidea# (Zygospyrida).

1. _Plectocoronis anacantha_, n. sp.

Basal ring and frontal ring elliptical, without sagittal constriction. Sagittal ring ovate. The frontal and sagittal rings are bordered on both edges with an incomplete series of small irregular pores. All three rings smooth, without spines.

_Dimensions._--Height of the frontal ring 0.1, breadth 0.16.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.

2. _Plectocoronis triacantha_, n. sp.

Basal ring and frontal ring nearly circular, without sagittal constriction. Sagittal ring elliptical, prolonged at the apex into an apical horn from which two branched lateral bows descend and unite with the uppermost parts of the frontal ring. Four other small bows descend from the lowermost parts of the latter and unite with the basal ring. From the lateral corners of the basal ring descend two short vertical feet. (May be regarded as derived from _Podocoronis toxarium_, Pl. 83, Fig. 7, by development of the bows connecting the rings.)

_Dimensions._--Height of the frontal ring 0.11, breadth 0.13.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

3. _Plectocoronis pentacantha_, n. sp. (Pl. 93, fig. 6).