Chapter XXXI: Section IV: STICHOCYRTIDA, Haeckel, 1862, Monogr. d. Radiol., p. 280, 312 (6)

The genus _Phæodina_ has the same structure of the central capsule as the majority of PHÆODARIA; one large main-opening or astropyle on the oral pole of the main axis, and two smaller lateral accessory openings or parapylæ on each side of the aboral pole: it is therefore a true Tripylean genus, like the majority of PHÆODARIA.

1. _Phæodina tripylea_, Haeckel (Pl. 101, fig. 2).

? _Tripylea_ sp., R. Hertwig, 1879, Organismus d. Radiol., Taf. x. figs.
1, 11.

Central capsule spheroidal or lenticular, somewhat depressed in the direction of the main axis. Astropyle with a strongly ribbed, radiate operculum, scarcely one-third as broad as the diameter of the capsule, and prolonged into a short tubular proboscis. Parapylæ also with short tubular openings. The outer strong (double-contoured) membrane of the central capsule is separated from the inner thin (simple-contoured) membrane by a wide interval, filled up by a clear fluid or jelly; only at the three apertures both membranes are in direct connection. The granulated protoplasm contains numerous vacuoles, and surrounds a large spheroidal nucleus, with numerous small nucleoli. The voluminous calymma in a specimen, observed living, was alveolar, and the ramification of the pseudopodia, as well as the formation of the dark brown phæodium, very similar to that of _Dictyocha stapedia_ (Pl. 101, fig. 10). Another specimen, figured in Pl. 101, fig. 2, exhibited the first stages of self-division; the reticulated nucleus and the radiate operculum of the astropyle were already doubled, and the two membranes of the capsule between them constricted in the median plane. To this species belong probably the central capsules figured by R. Hertwig, _loc. cit._

{1546}_Dimensions._--Diameter of the central capsule 0.15 to 0.25, of the nucleus 0.06 to 0.1, of the calymma 0.8 to 1.2.

_Habitat._--Mediterranean; Portofino, near Genoa (Haeckel); Messina (Hertwig).

2. _Phæodina cannopylea_, n. sp.

Central capsule subspherical, scarcely depressed in the direction of the main axis. Astropyle with a finely ribbed radiate operculum, about as broad as the radius of the capsule, prolonged into a slender, tubular proboscis which is S-shaped, about as long as the radius, and similar to that of _Phæocolla primordialis_, Pl. 101, fig. 1. Parapylæ also tubular, with two slender prolongations, half as long and broad as the proboscis of the parapyle. Nucleus spheroidal, about half as broad as the capsule. This species differs from the preceding mainly in the cylindrical slender prolongations of the three apertures, which are similar to those of _Aulosphæra_ and _Aularia_ (Pl. 111, fig. 2).

_Dimensions._--Diameter of the central capsule 0.2, of the nucleus 0.1, of the calymma 1.2 to 1.5.

_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms.

Family LXXII. #CANNORRHAPHIDA#, Haeckel, 1879 (Pl. 101, figs. 3-14; Pl. 114, figs. 7-13).

_Cannorrhaphida_, Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena,
Dec. 12, p. 4.

_Definition._--PHÆODARIA with an incomplete skeleton, composed of numerous separate, not radially arranged pieces, which are either hollow tangential spicula or cap-shaped dishes, or fenestrated rings, scattered loosely in the calymma. Central capsule placed in the centre of the spherical calymma.

The family #Cannorrhaphida# comprises those PHÆODARIA in which the incomplete skeleton is represented by numerous separate pieces of silica, which exhibit very different forms, and are scattered tangentially on the surface of the spherical calymma, sometimes also throughout its jelly-mass. They agree in this peculiar character with the Thalassosphærida (among the SPUMELLARIA) and bear the same relation to the skeletonless Phæodinida as the Thalassosphærida do to the Thalassicollida (compare pp. 10 and 29). The Cannorrhaphida represent the former group among the PHÆODARIA. They differ from the following family, the Aulacanthida, in the arrangement and position of the hollow spicula, which are never directed radially and never touch the central capsule, as is constantly the case in the latter.

Two genera of Cannorrhaphida have been hitherto known. The first species observed in a complete and living state (at Messina in 1859) was _Cannobelos cavispicula_, described in 1862 in my Monograph as _Thalassoplancta cavispicula_ (_loc. cit._, p. 261, Taf. iii. figs. 10-13). I there figured a complete living specimen with expanded pseudopodia and a double central capsule (in the stage of self-division). The latter was surrounded by an {1547}alveolar calymma and by a voluminous mass of blackish-brown pigment, the phæodium; numerous, long, hollow, cylindrical tubes were scattered on the surface of the calymma. At that time I did not know the tripylean character of the central capsule and the peculiar radiate operculum in the PHÆODARIA, and therefore placed _Thalassoplancta cavispicula_ among the Thalassosphærida.

The second description of a complete form of Cannorrhaphida was given in 1879 by R. Hertwig, under the name _Dictyocha fibula_ (Organismus d. Radiol., p. 89, Taf. ix. fig. 5). The genus _Dictyocha_ had been already founded by Ehrenberg in 1838, with the following definition:--"Lorica simplex, univalvis, silicea, laxe reticulata aut stellata" (Abhandl. d. k. Akad. d. Wiss. Berlin, 1838, p. 128). Ehrenberg had found only scattered pieces of the skeleton, fossil in Tertiary rocks. He placed them among the _Bacillaria_ (= _Diatomaceæ_), but added, that they may be possibly scattered spicula of Sponges ("forsan Spongiarum ossicula").

In 1859 I myself observed similar forms of _Dictyocha_ at Messina, and first recognised them as true Radiolaria. But I placed them at that time among the Acanthodesmida, beside _Prismatium_, supposing that a small spherical body which I had sometimes seen in the cavity of the pileated pieces (probably a phæodellum) was the small central capsule (Monogr. d. Radiol., 1862, p. 271, Taf. xii. figs. 3-6). The complete body of _Dictyocha_ was not described till 1879, when R. Hertwig gave a full description of its peculiar structure, and especially of the great central capsule, which resembles that of the other PHÆODARIA. He first stated that the singular pileated pieces described by Ehrenberg were not complete shells, but isolated pieces of the skeleton, which are scattered in the jelly-envelope around the central capsule in a mode similar to the spicula of _Thalassoplancta_, _Thalassosphæra_ and _Sphærozoum_. Hertwig also first recognised that the thin rods, which compose the reticular pileated pieces of the skeleton in _Dictyocha_, are not solid bars, but thin hollow tubules, similar to the hollow rods of _Aulacantha_ and of other PHÆODARIA.

Numerous complete and well-preserved specimens of _Dictyocha_, which I found in the collection of the Challenger, have convinced me that the accurate description of R. Hertwig is correct in every respect, and that these remarkable bodies are true PHÆODARIA, most closely allied to _Cannobelos_ (= _Thalassoplancta_) and to _Aulacantha_ (compare Pl. 101, fig. 10). I now regard them as representatives of a peculiar subfamily of Cannorrhaphida, which I call Dictyochida. To the same subfamily also belong the small annular bodies which Ehrenberg described in 1841 as _Mesocena_ (_loc. cit._, p. 401), and the elegant, more complicated, reticular and pileated bodies, which Stöhr figured in 1880 under the name _Distephanus_ (Palæontogr., vol. xxvi. p. 121). These peculiar bodies are also only isolated pieces of the siliceous skeleton, and are scattered tangentially in great numbers in the calymma, around the tripylean central capsule. A still higher degree of development is attained by the interesting forms {1548}which I describe here as _Cannopilus_ (Pl. 114, figs. 7-13). All these peculiar forms may be derived from the simple annular pieces of skeleton, which are aggregated in great numbers in the calymma of _Mesocena_. The pieces of the skeleton of these Dictyochida never assume the form of slender, cylindrical, tangential tubules which is characteristic of the Cannobelida.

A third subfamily of Cannorrhaphida, the Catinulida, is represented by the remarkable new genus _Catinulus_ (Pl. 117, fig. 8). The single pieces of the skeleton, scattered in hundreds or thousands throughout the calymma, are here not composed of hollow rods, as in the two former subfamilies, but are solid hemispherical caps, or small, more flatly vaulted dishes, with a peculiar radial striation. All the complete specimens of _Catinulus_ which I could examine possessed four equal central capsules, united in one spherical calymma.

The common character which unites the three rather different subfamilies, the Cannobelida, Dictyochida and Catinulida into a single family, and which separates this family, the Cannorrhaphida, from the other PHÆODARIA, is to be found in the composition of the rudimentary skeleton from numerous single pieces, which are loosely scattered either on the surface of the calymma, or throughout its jelly-mass, and which are never arranged radially and never touch the central capsule as is always the case in the closely allied Aulacanthida.

The slender spicula of the Cannobelida are cylindrical or spindle-shaped, tubular, scattered in variable numbers, but always in a tangential direction on the surface of the calymma. Usually they are 0.2 to 0.5 long, and 0.005 to 0.03 broad; either straight or slightly curved; smooth and simple in _Cannobelos_, spiny or branched in _Cannorrhaphis_ (Pl. 101, figs. 3-5). Their wall is thin and fragile, their diameter sometimes equal throughout their whole length, at other times tapering towards both ends. Their cavity is filled by jelly, and seems to be open at both ends, since the purified and dried spicula constantly become filled by air.

The peculiar pieces of silica which compose the skeleton of the Catinulida are not hollow, like the rods of the other Cannorrhaphida, but concave hemispherical cups or more flatly vaulted little dishes, the thin flinty wall of which is slightly thickened at the circular margin, and radially striped above it. In all three species of _Catinulus_ observed they were scattered throughout the calymma in hundreds or thousands (Pl. 117, fig. 8). Their relation to the Dictyochida is doubtful. Perhaps the small cups of _Catinulus_ may be derived from the simple rings of _Mesocena_, by development of an operculum on one side of the ring.

The skeleton of the Dictyochida is much more developed and possesses a higher morphological interest; the numerous different forms, however, which its pieces here assume, may be all derived from the simple circular ring of _Mesocena_. This ring is formed by a thin, hollow, cylindrical, or prismatic rod, sometimes circular or elliptical, at {1549}other times polygonal. From its margin small, hollow, radial spines often proceed (Pl. 101, fig. 9). In _Dictyocha_ there arise from the ring two, three, four or more siliceous bars or arches, which form one or more bulges over one side of the ring; usually the little fenestrated shell thus produced assumes the form of a three-sided or four-sided pyramid, or of a little hat with three or four meshes (Pl. 101, figs. 10-14). From this _Dictyocha_ (in a restricted sense) we separate the genus _Distephanus_, in which the little pyramids become truncated, so that one central apical mesh (the apical or upper ring) is surrounded by four, five, six or eight lateral meshes, the sides of the pyramid (Pl. 114, figs. 7-9). The edges of the small pyramid are formed by the same number of siliceous bars arising from the ring and alternating with the meshes. Radial spines in different numbers and arrangements arise from the corners of the two parallel rings, as well from the smaller apical as from the larger basal ring. The simple apical ring of _Distephanus_ becomes divided or fenestrated in the highest developed genus of this subfamily, in _Cannopilus_ (Pl. 114, figs. 10-13); each pileated piece of the skeleton exhibits here two rows of alternating lateral meshes, an upper row of smaller and a lower row of larger meshes.

The majority of Dictyochida are armed with spines or thorns, which arise in a regular manner from different points of the annular or pileated pieces. In the ancestral genus, _Mesocena_, radial spines start from the corners of the simple ring in centrifugal direction, and lie horizontally in its plane. As these primary corner-spines determine the radial composition of the more highly developed genera we call them perradial (lying in rays of the first order). In _Dictyocha_ and _Distephanus_ commonly (but not quite constantly) these perradial spines alternate with the ascending bars which bisect the sides of the basal ring; these bars are therefore interradial (lying in rays of the second order); consequently also the corners of the apical ring of _Distephanus_ are interradial. The latter also often bear small thorns or teeth. Other teeth frequently start in centripetal direction from the lower or basal ring, on the side of the perradial spines, and frequently they are directed obliquely downwards.

In _Dictyocha_ and _Distephanus_ are frequently found remarkable twin pieces, composed of two pileated and reticulated skeleton pieces. These are united by their basal rings loosely in such a way that they form together a small fenestrated subspherical body; the union is strengthened by those small teeth of the basal rings, which are directed downwards and catch one into the other (Pl. 101, fig. 12; Pl. 114, fig. 8). A similar twin piece has been already observed by Stöhr in the fossil _Distephanus rotundus_, and upon this was founded this genus. Since the teeth of the two opposed basal rings, catching one into the other, seem to be specially adapted for the composition of those small double pyramids, it is probable that the latter possess a special protective function in these PHÆODARIA, and perhaps envelop their phæodella or their flagellate spores (?). In every case these formations are very remarkable.

{1550}_The Central Capsule_ of the Cannorrhaphida seems to possess the same shape in the three subfamilies, and to agree in general with that of the Aulacanthida. In a living specimen of _Dictyocha stapedia_, which I observed at Ceylon (Pl. 101, fig. 10), the three openings of the TRIPYLEA were distinct; the radiate operculum of the astropyle (on the oral pole) was surrounded by the granules of the dark phæodium, whilst on the opposite aboral side, two parapylæ or conical secondary openings were visible. The voluminous spherical calymma (about four times as broad as the central capsule) contained numerous large alveoles (as in _Aulosphæra_) and its surface was protected by numerous pileated pieces of the skeleton; the basal ring of the latter was placed tangentially in the spherical surface of the calymma, their apical spine being directed outwards. The pseudopodia, arising from the central capsule and forming a network between the alveoles of the calymma, radiated outwards in great number from its surface (Pl. 101, fig. 10).

The propagation by self-division seems to be very frequent in the Cannorrhaphida. I frequently found two equal central capsules in one calymma, as in the first observed species, _Cannobelos cavispicula_, and in _Cannorrhaphis spinulosa_ (Pl. 101, fig. 3), sometimes also in _Dictyocha_ and _Distephanus_. As already mentioned, _Catinulus_ constantly exhibited four central capsules united in each calymma.

_Synopsis of the Genera of Cannorrhaphida._

-------------------------------------------------------------------------
I. Subfamily Cannobelida.
Pieces of the skeleton cylindrical or spindle-shaped tangential
tubules.
-------------------------------------------------------------------------
Tubules simple, smooth, 658. _Cannobelos_.

Tubules spiny or branched, 659. _Cannorrhaphis_.
-------------------------------------------------------------------------
II. Subfamily Catinulida.
Pieces of the skeleton hemispherical or cap-shaped, solid.
-------------------------------------------------------------------------
Caps or hemispherical pieces of the skeleton
solid, with radiate margin and circular opening, 660. _Catinulus_.
-------------------------------------------------------------------------
III. Subfamily Dictyochida.
Pieces of the skeleton either simple rings or pileated or pyramidal
bodies, composed of thin hollow rods and reticular meshes.
-------------------------------------------------------------------------
Flinty pieces simple { Basal ring simple, not
or arched rings, not { arched or fenestrated, 661. _Mesocena_.
truncated pyramids, {
with a basal ring, { Basal ring fenestrated,
but without apical { with two or more arches,
ring. { vaulted over one side, 662. _Dictyocha_.

Flinty pieces of the { Apical ring simple, not
skeleton resembling { fenestrated (one girdle
a truncated pyramid, { of meshes on each piece), 663. _Distephanus_.
with an upper smaller {
apical ring, and a { Apical ring fenestrated
lower larger basal { (two girdles of meshes
ring. { on each piece), 664. _Cannopilus_.

{1551}Subfamily 1. CANNOBELIDA, Haeckel.

_Definition._--#Cannorrhaphida# with numerous hollow cylindrical or spindle-shaped tubes, which lie tangentially scattered on the surface of the spherical calymma.

Genus 658. _Cannobelos_,[276] n. gen.

_Definition._--#Cannorrhaphida# with a skeleton composed of tubular acicular pieces, which are smooth, cylindrical or spindle-shaped tangential needles, without spines and branches.

The genus _Cannobelos_, and the following closely allied _Cannorrhaphis_, represent the peculiar subfamily Cannobelida, differing from the other Cannorrhaphida in the acicular form of the pieces of the skeleton, which are tangentially scattered on the surface of the spherical calymma. The cylindrical or spindle-shaped hollow needles are smooth in _Cannobelos_, whilst in _Cannorrhaphis_ they are studded with lateral spines or branches.

1. _Cannobelos cavispicula_, Haeckel.

_Thalassoplancta cavispicula_, Haeckel, 1862, Monogr. d. Radiol., p. 261,
Taf. iii. figs. 10-13.

_Thalassicolla cavispicula_, Haeckel, 1860, Monatsber. d. k. preuss.
Akad. d. Wis. Berlin, p. 798.

_Cannorrhaphis cavispicula_, Haeckel, 1881, Prodromus, p. 470.

Tangential tubes cylindrical, more or less curved, gradually tapering towards the two pointed ends. Calymma with a voluminous phæodium.

_Dimensions._--Length of the tubular spicule 0.25, breadth 0.003.

_Habitat._--Mediterranean, Messina, surface.

2. _Cannobelos calymmata_, n. sp.

Tangential tubes cylindrical, straight, of equal breadth throughout their whole length, closed by a hemispherical cap on the two rounded ends. Calymma very voluminous, with a small phæodium.

_Dimensions._--Length of the tubular spicula 0.3 to 0.5, breadth 0.004 to 0.008.

_Habitat._--Central Pacific, Stations 263 to 274, surface.

3. _Cannobelos thalassoplancta_, n. sp.

Tangential tubes spindle-shaped, straight, gradually tapering towards the two pointed ends. Calymma and the included phæodium rather voluminous.

_Dimensions._--Length of the tubular spicula 0.15 to 0.2, breadth in the middle part 0.02.

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

{1552}Genus 659. _Cannorrhaphis_,[277] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 4.

_Definition._--#Cannorrhaphida# with a skeleton composed of tubular acicular pieces, which are spiny, cylindrical or spindle-shaped tangential needles, either with lateral spines or branches.

The genus _Cannorrhaphis_ differs from the preceding closely allied _Cannobelos_ in the spiny shape of the tangential acicular spicula, which are studded either with short spines or with longer lateral branches.

1. _Cannorrhaphis spinulosa_, n. sp. (Pl. 101, figs. 3, 4).

Tangential tubes cylindrical, straight, gradually tapering towards the two pointed ends, densely studded with conical spines, arising perpendicularly. (The specimen figured, fig. 3, exhibited two ovate central capsules, each of which contained two large nuclei, with numerous nucleoli.)

_Dimensions._--Length of the tubular spicula 0.3 to 0.5, breadth 0.01 to 0.015.

_Habitat._--North Pacific, Station 244, surface.

2. _Cannorrhaphis lampoxanthium_, n. sp.

Tangential tubes cylindrical, more or less curved, suddenly tapering towards the two pointed ends, densely studded with irregular conical spines of unequal length, which arise obliquely from their surface.

_Dimensions._--Length of the tubular spicula 0.4 to 0.5, breadth 0.005 to 0.008.

_Habitat._--South Pacific, Station 289, depth 2550 fathoms.

3. _Cannorrhaphis lappacea_, n. sp.

Tangential tubes spindle-shaped, gradually tapering towards the two pointed ends, densely studded with irregular lateral branches, which are partly simply, partly forked, more or less curved, and arise obliquely from their surface.

_Dimensions._--Length of the tubular spicula 0.2 to 0.3, breadth 0.015 to 0.025.

_Habitat._--Central Pacific, Station 271, surface.

4. _Cannorrhaphis spathillata_, n. sp. (Pl. 101, fig. 5).

Tangential tubes cylindrical, thin and straight, regularly zigzag, with pointed, regularly alternating lateral spines, with an elegant spathilla, or a cap-shaped verticil of eight to ten recurved spines on the two ends.

_Dimensions._--Length of the tubular spicula 0.3, breadth 0.003.

_Habitat._--Indian Ocean, Cocos Islands (Rabbe), surface.

{1553}Subfamily 2. CATINULIDA, Haeckel.

_Definition._--#Cannorrhaphida# with a skeleton composed of numerous cap-shaped pieces, which lie tangentially scattered on the surface of the spherical calymma. Each piece is a hemispherical or flatly cap-shaped siliceous body, often with radial striations, and with a thin solid wall.

Genus 660. _Catinulus_,[278] n. gen.

_Definition._--#Cannorrhaphida# with a skeleton composed of solid, cap-shaped or hemispherical, not fenestrated, pieces.

The genus _Catinulus_ differs from all the other Cannorrhaphida in the peculiar shape of the numerous siliceous pieces, which are scattered on the surface of the calymma and compose their rudimentary skeleton. These pieces are neither hollow rings (as in the Dictyochida), nor hollow tubes (as in the Cannobelida), but solid hemispherical caps or more flatly vaulted small dishes. All the complete specimens of this genus which I observed exhibited four equal central capsules in the spherical calymma.

1. _Catinulus quadrifidus_, n. sp. (Pl. 117, figs. 8, 8_a_).

Cap-shaped pieces of the skeleton flatly vaulted, three times as broad as high, smooth; the marginal ring with fine radial ribs and with smooth margin.

_Dimensions._--Diameter of the calymma 0.6 to 0.8, of the four central capsules 0.12 to 0.2; breadth of the concave caps 0.024, height 0.008.

_Habitat._--South Atlantic, Station 323, depth 1900 fathoms.

2. _Catinulus catillum_, n. sp.

Cap-shaped pieces of the skeleton flatly vaulted, three times as broad as high, rough, covered with numerous small spinules; the marginal ring with stout radial ribs and a corona of denticles on the margin.

_Dimensions._--Breadth of the concave caps 0.03, height 0.01.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

3. _Catinulus lopadium_, n. sp.

Cap-shaped pieces of the skeleton hemispherical, twice as broad as high, smooth; the marginal ring smooth, slightly radiate, with thickened smooth margin.

_Dimensions._--Diameter of the calymma 1.2, of the central capsule 0.22; breadth of the concave caps 0.024, height 0.012.

_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms.

{1554}Subfamily 3. DICTYOCHIDA, Haeckel.

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

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

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

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

{1555}1. _Mesocena circulus_, Ehrenberg.

_Mesocena circulus_, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 208.

_Mesocena circulus_, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 44.

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

_Dimensions._--Diameter of the rings 0.02 to 0.03, thickness of the hollow rod 0.001 or less.

_Habitat._--Fossil in Tertiary rocks of Barbados and of the Mediterranean (Ægina, Greece; Caltanisetta, Sicily).

2. _Mesocena annulus_, n. sp.

? _Mesocena crenulata_, Ehrenberg, 1860, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 822.

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

_Dimensions._--Diameter of the rings in the major axis 0.03, in the minor 0.02; thickness of the bars 0.002.

_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms.

3. _Mesocena diodon_, Ehrenberg.

_Mesocena diodon_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 84.

_Mesocena diodon_, Ehrenberg, 1854, Mikrogeol., Taf. xxxiii., Nr. xv.
fig. 18.

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

_Dimensions._--Diameter of the rings in the major axis 0.04, in the minor 0.03; length of the spines 0.01.

_Habitat._--Fossil in Barbados, and in North America (Virginia).

4. _Mesocena triangula_, Ehrenberg.

_Mesocena triangula_, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 208.

_Mesocena triangula_, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 41.

_Dictyocha triangula_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 46.

_Lithocircus triangularis_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 121,
Taf. vii. fig. 10.

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

_Dimensions._--Diameter of the rings 0.03 to 0.05, length of the spines 0.01.

_Habitat._--Fossil in Tertiary deposits of the Mediterranean; Caltanisetta, Sicily (Ehrenberg, Stöhr).

{1556}5. _Mesocena quadrangula_, Ehrenberg.

? _Mesocena quadrangula_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, pp. 145, 273.

? _Mesocena quaternaria_, Ehrenberg, 1855, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 302.

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

_Dimensions._--Diameter of the rings 0.02 to 0.025, length of the spines 0.007 to 0.01.

_Habitat._--North Atlantic, Færöe Channel, Gulf Stream (John Murray), depth 600 fathoms.

6. _Mesocena elliptica_, Ehrenberg.

_Mesocena elliptica_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 84.

_Mesocena elliptica_, Ehrenberg, 1854, Mikrogeol., vol. i. Taf. xx. fig.
44.

_Dictyocha elliptica_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 44.

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

_Dimensions._--Diameter of the rings 0.015 to 0.03, length of the spines 0.005.

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

7. _Mesocena pentagona_, n. sp.

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

_Dimensions._--Diameter of the rings 0.02, length of the spines 0.005.

_Habitat._--Fossil in Barbados.

8. _Mesocena hexagona_, Haeckel.

? _Mesocena senaria_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, pp. 163, 273.

? _Mesocena septenaria_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, pp. 163, 273.

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

_Dimensions._--Diameter of the rings 0.025 to 0.03, length of the spines 0.007 to 0.01.

_Habitat._--Mediterranean, Krim (Ehrenberg), Corfu (Haeckel).

{1557}9. _Mesocena octogona_, Ehrenberg.

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

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

? _Mesocena heptagona_, Ehrenberg, 1854, Mikrogeol., Taf. xx. fig. 49.

? _Mesocena octoradiata_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, pp. 163, 273.

? _Mesocena nonaria_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, pp. 163, 273.

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

_Dimensions._--Diameter of the rings 0.02, length of the spines 0.005.

_Habitat._--Tropical Pacific; Peru, Ehrenberg; Station 272 to 274, surface.

10. _Mesocena bisoctona_, Ehrenberg.

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

_Mesocena binonaria_, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 78, _loc. cit._

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

_Dimensions._--Diameter of the rings 0.02, length of the outer spines 0.005.

_Habitat._--Fossil in Guano from Peru and South Africa, also in Barbados.

11. _Mesocena stellata_, n. sp. (Pl. 101, fig. 9).

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

_Dimensions._--Diameter of the rings 0.03, length of the larger spines 0.01.

_Habitat._--Central area of the Pacific, Station 270, depth 2925 fathoms.

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

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

The genus _Dictyocha_ is a very remarkable and interesting form of PHÆODARIA, which has had a curious history. Ehrenberg, who first observed single pieces of it fossil in Tertiary rocks, supposed it to be the siliceous carapace of a Diatom, and gave it the following {1558}diagnosis: "Dictyocha, e familia Bacillariorum. Lorica simplex univalvis silicea, laxe reticulata aut stellulata" (_loc. cit._). In my Monograph (1862, p. 271), I placed it in the class Radiolaria, supposing that it might be a simple form of Acanthodesmida, having found only isolated siliceous pieces. Afterwards (in 1879) Richard Hertwig observed the entire living body, and demonstrated that the hollow siliceous pieces are scattered in great numbers around a tripylean central capsule, which exhibits all the essential characters of PHÆODARIA (Organismus d. Radiol., 1879, p. 89). Hertwig describes the position of the numerous siliceous pieces in the surface of the extracapsular jelly-sphere so densely aggregated, that they touch one another and produce the appearance of a reticulated sphere. In two specimens, which I observed living (Pl. 101, fig. 10), and in numerous complete specimens which I found in the collection of the Challenger, the number of the siliceous pieces was much smaller, and they were scattered irregularly in the surface of the alveolate jelly-sphere, being separated by wide and unequal intervals. The regular position seems to be that the basal rings lie tangentially in the spherical surface of the calymma, whilst the bars of the reticulum are directed outwards, and the apical spine radially in centrifugal direction. Very often two pieces are united by their basal rings in such a manner that they form a little spheroidal fenestrated body (as in _Distephanus_, Stöhr; compare p. 1550). The characteristic reticular skeleton-pieces of _Dictyocha_ must be derived from _Mesocena_; from its simple siliceous ring (on one side of its plane), arise two, three, or four (rarely more) bars, which become united to a loose framework (with two, three, or four meshes). When this network assumes the form of a truncated pyramid (with a central mesh on the apex), _Dictyocha_ passes over into _Distephanus_. From the corners of the original basal ring several radial spines usually arise in a centrifugal direction, and on the sides of these sometimes small teeth or thorns also run in a centripetal direction. The number of the meshes and the separating rods is usually four, more rarely two or three. The hollow rods are very thin, either cylindrical or prismatic. As the ascending rods alternate regularly with the corner-spines of the basal ring, we may call the latter perradial, the former interradial. Ehrenberg has distinguished in his genus _Dictyocha_ not less than fifty species, thirty-five living and twenty-five fossil (ten species both living and fossil). The greater part of these cannot be retained, as they are only slight varieties or abnormalities of single pieces of the skeleton, such as very frequently occur associated with the common regular forms in one and the same individual. Such abnormal species are, _e.g._, _Dictyocha abnormis_, _Dictyocha binoculus_, _Dictyocha bipartita_, _Dictyocha haliomma_, _Dictyocha hexathyra_, _Dictyocha septenaria_, &c. One species (_Dictyocha splendens_), is the fenestrated calcareous body of a Holothurian. Of some other species Ehrenberg has only given the name, but neither a description nor a figure (e.g., _Dictyocha borealis_, _Dictyocha cenostephania_, _Dictyocha compos_, _Dictyocha coronata_, _Dictyocha socialis_, _Dictyocha specillum_). A number of other species must be placed in the genera _Distephanus_ and _Cannopilus_, so that only eight of his species of true _Dictyocha_ remain.

{1559}1. _Dictyocha navicula_, Ehrenberg.

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

_Dictyocha ponticulus_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 267.

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

_Dimensions._--Diameter of the ring 0.02, of the bars 0.001.

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

2. _Dictyocha quadrata_, Ehrenberg.

_Dictyocha quadrata_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 267.

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

_Dimensions._--Diameter of the ring 0.015.

_Habitat._--Atlantic, Bermuda Islands; fossil in Barbados.

3. _Dictyocha pons_, Ehrenberg.

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

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

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

_Dimensions._--Diameter of the ring 0.01, of the bars 0.001.

_Habitat._--Fossil in Tertiary rocks, Oran, Africa.

4. _Dictyocha triommata_, Ehrenberg.

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

_Dictyocha triactis_ (= _triacantha_), Ehrenberg, 1844, Monatsber. d. k.
preuss. Akad. d. Wiss. Berlin, p. 80.

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

_Dictyocha abyssorum_, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 38.

Each pileated piece of the skeleton is a small three-sided pyramid, the sides of which form three triangular meshes; the three edges between them are three curved interradial beams, united in the {1560}centre (the apex of the pyramid). Alternating with these, three horizontal, perradial, centrifugal spines start from the base.

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

_Dimensions._--Diameter of the basal triangle 0.01, of the three meshes 0.005.

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

5. _Dictyocha tripyla,_ Ehrenberg.

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

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

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

_Dimensions._--Diameter of the triangular basal ring 0.015, of the three meshes 0.007.

_Habitat._--Fossil in Tertiary deposits. North Africa (Oran), Sicily (Caltanisetta).

6. _Dictyocha medusa_, n. sp. (Pl. 101, figs. 13, 14).

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

_Dimensions._--Diameter of the basal ring 0.02, of the four meshes 0.01.

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

7. _Dictyocha staurodon_, Ehrenberg.

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

_Dictyocha staurodon,_ Ehrenberg, 1854, Mikrogeol., Taf. xviii. fig. 58.

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

_Dimensions._--Diameter of the basal ring 0.025, of the meshes 0.01.

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

{1561}8. _Dictyocha fibula_, Ehrenberg.

_Dictyocha fibula_, Ehrenberg, 1839, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 149; Mikrogeol., Taf. xviii. fig. 54, _a_, _b_, _c_, Taf. xix.
fig. 43, Taf. xx. fig. 45, Taf. xxi. fig. 42, &c.

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

_Dictyocha bipartita_, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 44.

_Dictyocha tenella_, Ehrenberg, 1841, Abhandl. d. k. Akad. d. Wiss.
Berlin, Taf. ii. fig. 11.

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

_Dimensions._--Diameter of the basal square ring (diagonal) 0.01 to 0.02, of the meshes 0.005.

_Habitat._--Fossil in different Tertiary rocks (Barbados, Oran, Greece, Sicily, &c.), Ehrenberg.

9. _Dictyocha messanensis_, Haeckel.

_Dictyocha messanensis_, Haeckel, 1862, Monogr. d. Radiol., p. 272, Taf.
xii. figs. 3-6.

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

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

_Dimensions._--Diameter of the basal ring 0.02 to 0.03, of the meshes 0.01 to 0.016.

_Habitat._--Mediterranean (Messina), North Atlantic (Canary Islands), Station 354, surface.

10. _Dictyocha epiodon_, Ehrenberg.

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

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

_Dimensions._--Diameter of the basal ring 0.03, of the meshes 0.01.

_Habitat._--Fossil in Tertiary rocks of North America (Miocene Tripel of Richmond, Virginia, &c.).

11. _Dictyocha stapedia_, n. sp. (Pl. 101, figs. 10-12).

Each pileated piece of the skeleton stirrup-shaped, with four paired meshes, similar to the hats of _Dictyocha fibula_ and _Dictyocha messanensis_, but distinguished by four small centripetal teeth, which start from the inside of the basal ring, at the side of the four ascending beams. In the centre of the diagonal arch arises a vertical apical spine (differing from _Dictyocha epiodon_). This species seems {1562}to be the most common of the living forms and widely distributed over all warmer seas. I observed in Ceylon, taken on the surface, the living specimen figured in Pl. 101, fig. 10, the numerous spicula were irregularly scattered over the spherical surface of the alveolate calymma. Other specimens occur in various preparations of the Challenger collection, from the Atlantic and the Pacific. The majority of the siliceous little hats exhibited the stirrup-form shown in fig. 11, and many were united in pairs, forming a twin-piece (fig. 12). Intermingled with these are found some irregular forms, representing the specific form of some allied species, viz., _Dictyocha speculum_, _Dictyocha staurodon_, _Dictyocha epiodon_ and _Dictyocha messanensis_.

_Dimensions._--Diameter of the basal ring 0.015 to 0.03, of the meshes 0.005 to 0.012.

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

12. _Dictyocha rhombus_, n. sp.

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

_Dimensions._--Diameter of the basal ring 0.02, of the meshes 0.005 to 0.01.

_Habitat._--North Atlantic; Færöe Channel, Gulf Stream, depth 50 to 600 fathoms, John Murray.

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

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

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

{1563}The genus _Distephanus_ of Stöhr, therefore, is nothing other than the _Dictyocha_ of Ehrenberg. But I think it is more convenient to retain the name _Distephanus_ for those forms of _Dictyocha_ which possess a simple apical mesh surrounded by a ring of lateral meshes, and in which each piece of the skeleton forms a small truncated pyramid. The basal plane of this pyramid is marked by the original basal ring (_Mesocena_), the truncated upper plane by the parallel apical ring, and the edges of the pyramid by the rising bars which connect both rings. In this sense, so far as the two rings lying in parallel planes are concerned, the term _Distephanus_ is correct (but not in the original sense of Stöhr). The number of the rising bars between the two rings varies from four, five, six to eight or more. It seems rather constant in each species, so that all the pieces of the skeleton of one specimen possess either four or six or eight lateral meshes, &c. But sometimes individual irregularities occur. In the majority of species each skeleton-piece is armed with spines. Usually a radial horizontal spine starts centrifugally from each corner of the basal ring, and on the side of this a small tooth or thorn often starts centripetally or downwards. In the twin-pieces, where the two basal rings are united, these teeth catch into one another. In some species upper spines also occur, starting from the corners of the apical ring. The perradial spines of the corners of the basal ring alternate regularly with the interradial ascending bars, which bisect the sides of the ring, as in _Dictyocha_.

1. _Distephanus crux_, Haeckel.

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

_Dictyocha bipartita_, Ehrenberg, 1844, _loc. cit._, p. 79, Taf. xxii.
fig. 44.

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

_Dimensions._---Diameter of the basal ring 0.02 to 0.03, of the apical ring 0.008.

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

2. _Distephanus mesophthalmus_, Haeckel.

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

Each pileated piece of the skeleton exhibits four lateral meshes around the central mesh, and is composed of two parallel horizontal square rings, like those of _Distephanus crux_, but distinguished {1564}from this by eight short teeth, four centripetal on the larger lower ring and four perradial centrifugal on the smaller upper ring.

_Dimensions._--Diameter of the basal ring 0.03, of the apical ring 0.015.

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

3. _Distephanus stauracanthus_, Haeckel.

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

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

_Dimensions._--Diameter of the basal ring 0.03, of the apical ring 0.004.

_Habitat._--Fossil in Tertiary rocks of North America (Hollis Cliff, Virginia; Norwich, Connecticut).

4. _Distephanus asteroides_, n. sp.

_Dictyocha asteroides_, Haeckel, 1881, Prodromus.

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

_Dimensions._--Diameter of the basal ring 0.02, of the apical ring, 0.007.

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

5. _Distephanus pentasterias_, Haeckel.

_Dictyocha pentasterias_, Ehrenberg, 1839, Mikrogeol., Taf. xviii. fig.
61.

? _Dictyocha quinaria_, Ehrenberg, 1842, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 265.

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

_Actiniscus elegans_, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 51.

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

_Dimensions._--Diameter of the basal ring 0.012 to 0.018, of the apical ring 0.002 to 0.003.

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

{1565}6. _Distephanus speculum_, Haeckel.

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

_Dictyocha speculum_, Stöhr, 1880, Palæontogr., vol. xxvi., Taf. vii.
fig. 8.

_Dictyocha anacantha_, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 238.

_Dictyocha diommata_, Ehrenberg, 1854, Mikrogeol., Taf. xxxiii., Nr.
xvii. fig. 6.

_Dictyocha erebi_, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 238.

_Dictyocha haliomma_, Ehrenberg, 1844, Mikrogeol., 1854. Taf. xxi. fig.
46.

_Dictyocha hexathyra_, Ehrenberg, 1844, Mikrogeol., 1854, Taf. xxii. fig.
46.

_Dictyocha ubera_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 80.

_Dictyocha stella_, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 52.

_Dictyocha rotundus_, Stöhr, 1880, Palæontogr., vol. xxvi., Taf. vii.
fig. 9.

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

_Dimensions._--Diameter of the basal ring 0.03, of the apical ring 0.01.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; fossil in Barbados, Sicily, &c.

7. _Distephanus ornamentum_, Haeckel.

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

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

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

_Dimensions._--Diameter of the basal ring 0.03, of the apical ring 0.015.

_Habitat._--Fossil in Tertiary deposits of Sicily, Caltanisetta (Ehrenberg).

8. _Distephanus aculeatus_, Haeckel.

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

_Dictyocha aculeata_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 120, Taf.
vii. fig. 7.

_Dictyocha bisternaria_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 201.

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

_Dimensions._--Diameter of the basal ring 0.02, of the apical ring 0.008.

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

{1566}9. _Distephanus sirius_, Haeckel.

_Actiniscus sirius_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 68.

_Dictyocha sirius_, Ehrenberg, 1854, Mikrogeol., Taf. xviii. fig. 59.

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

_Dimensions._--Diameter of the basal ring 0.02, of the apical ring 0.005.

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

10. _Distephanus corona_, n. sp. (Pl. 114, figs. 7-9).

_Dictyocha corona_, Haeckel, 1881, Prodromus.

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

_Dimensions._--Diameter of the basal ring 0.025 to 0.03, of the apical ring 0.012 to 0.02.

_Habitat._--North-west Pacific, Sea of Japan, Station 231, depth 2250 fathoms.

11. _Distephanus octonarius_, Haeckel.

_Dictyocha octonaria_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 201.

_Dictyocha polyactis_, Ehrenberg, 1844, _loc. cit._, p. 80; Mikrogeol.,
1854, Taf. xxii. fig. 50.

_Dictyocha septenaria_, Ehrenberg, 1844, _loc. cit._, p. 80; Mikrogeol.,
1854, Taf. xxi. fig. 45.

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

_Dimensions._--Diameter of the basal ring 0.02 to 0.03, of the apical ring 0.01 to 0.015.

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

{1567}12. _Distephanus octogonius_, n. sp.

_Dictyocha septenaria_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvA., Nr.
xxi. fig. 8.

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

_Dimensions._--Diameter of the basal ring 0.02, of the apical ring 0.012.

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

13. _Distephanus diadema_, n. sp.