Chapter XI: Literature and History (12)

The genus _Leptosphæra_, together with the three following genera, forms the very peculiar and typical small group of #Sphæroidea# which we call the Diplosphærida (with four genera and twenty-four species); their shell is composed of two concentric spheres as in the three foregoing genera; but whilst in these the inner shell is an intracapsular medullary shell and the outer an extracapsular cortical shell, in the Diplosphærida {244}both shells are extracapsular or cortical shells, therefore the inner shell of the latter corresponds to the outer of the former. The inner spherical shell of all Diplosphærida is composed of very delicate beams and large pores, which are either regular hexagonal or irregular polygonal (never roundish). From its surface arise a variable number (twenty to thirty) of stout long radial spines, which are invariably longer than the shell diameter (often two to three times as long or more), and of three-sided prismatic form, the three edges either smooth or serrate, often with three rows of lateral branches (commonly three to five branches in each row); the latter are invariably of the same form, concavely curved towards the spine, and decrease in size towards the distal end. From the three edges of each main spine in all Diplosphærida, at equal distances from the centre, arise six very thin, thread-like lateral branches (a pair from each edge) and connect the spine in a tangential direction with all neighbouring spines. In this manner the polyhedral outer shell is formed, the meshes of which therefore are always very large and triangular. Sometimes each of these primary triangular meshes becomes filled up with a secondary network, either of regular quadrangular or of irregular polygonal secondary meshes. Besides the constant twenty to thirty large main spines, in the majority of Diplosphærida bristle-shaped radial by-spines arise, either from the inner shell (_Diplosphæra_) or from the outer (_Drymosphæra_), or from both (_Astrosphæra_). They are absent only in _Leptosphæra_. Commonly the by-spines are simple, rarely forked or branched. The central capsule in the Diplosphærida is usually enclosed in the inner shell; often it completely fills up the latter, or drives out a cæcal protuberance through each mesh; but these processes rarely unite outside. The average size of the Diplosphærida, which are all pelagic organisms, is much larger than that of the other Haliommida.

Subgenus 1. _Leptosphærella_, Haeckel.

_Definition._--Radial spines simple, without lateral branches.

1. _Leptosphæra hexagonalis_, n. sp. (Pl. 19, fig. 2).

Inner shell with regular, hexagonal meshes, and very thin, thread-like bars; outer shell twice as broad, with simple triangular meshes. Radial spines with three smooth edges. (Fig. 2 represents the central capsule with numerous club-shaped saccules, prominent externally through the meshes; in the centre a large simple spherical nucleus, one-third as broad as the capsule. The skeleton of this species is identical with that of _Diplosphæra hexagonalis_, Pl. 19, fig. 3, but has no by-spines.)

_Dimensions._--Diameter of the outer shell 0.3, of the inner 0.15.

_Habitat._--Cosmopolitan; Mediterranean (Corfu), North Atlantic (Canary Islands), Tropical Pacific, surface.

{245}2. _Leptosphæra serrata_, n. sp.

Inner shell with regular, hexagonal meshes, five to six times as broad as the bars; outer shell three times as broad, with simple triangular meshes. Radial spines with three serrated edges (of the same form as the main spines of _Drymosphæra dendrophora_, Pl. 20, fig. 1).

_Dimensions._--Diameter of the outer shell 0.45, of the inner 0.15.

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

3. _Leptosphæra polygonalis_, n. sp.

Inner shell with irregular, polygonal meshes and very thin thread-like bars; outer shell twice as broad, with simple triangular meshes. Radial spines with three smooth edges. (Resembles _Drymosphæra polygonalis_, Pl. 19, fig. 1, but has no by-spines.)

_Dimensions._--Diameter of the outer shell 0.35, inner 0.175.

_Habitat._--North Pacific, Station 256, surface.

Subgenus 2. _Leptosphæromma_, Haeckel.

_Definition._--Radial spines with three rows of lateral branches (one row on each edge).

4. _Leptosphæra ciliata_, n. sp.

Inner shell with regular, hexagonal meshes and very thin thread-like bars; outer shell three times as broad, with simple triangular meshes. Radial spines with smooth edges and three rows of simple, smooth, curved, lateral branches (six branches on each edge), similar to those of _Diplosphæra gracilis_.

_Dimensions._--Diameter of the outer shell 0.6, inner 0.2.

_Habitat._--South Atlantic, Station 325, surface.

5. _Leptosphæra spinosa_, Haeckel.

_Diplosphæra spinosa_, R. Hertwig, 1879, Organismus d. Radiol., p. 40,
Taf. v. fig. 2.

Inner shell with regular, hexagonal meshes, five times as broad as the bars; outer shell three times as broad, with simple triangular meshes. Radial spines with three densely serrated edges, and with three rows of serrated, simple, curved, lateral branches (three branches on each edge). Differs from the preceding in the thicker bars and the elegantly denticulated spines and branches.

_Dimensions._--Diameter of the outer shell 0.66, inner 0.22.

_Habitat._--Mediterranean (Messina), R. Hertwig.

6. _Leptosphæra stellata_, n. sp.

Inner shell with regular, hexagonal meshes, six times as broad as the bars, each bar crossed by a transverse tangential rod, so that each mesh represents an elegant six-rayed star (as {246}in _Astrosphæra stellata_, Pl. 19, fig. 5, but without radial by-spines); outer shell twice as broad, with simple triangular meshes. Radial spines with serrated edges and three rows of simple lateral branches (four branches on each edge).

_Dimensions._--Diameter of the outer shell 0.44, inner 0.22.

_Habitat._--Tropical Atlantic (Ascension Island), Station 343, surface.

7. _Leptosphæra reticulum_, n. sp.

Inner shell with irregular, polygonal meshes and very thin thread-like bars; outer shell four times as broad, also with irregular, polygonal meshes, the sides of the triangular main meshes being connected by irregular lateral ramules, forming an extremely delicate reticulum.

_Dimensions._--Diameter of the outer shell 0.64, inner 0.16.

_Habitat._--South Pacific, Station 291, surface.

Genus 98. _Diplosphæra_,[133] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 804.

_Definition._--#Astrosphærida# with two extracapsular cortical shells, connected by long, prismatic, radial spines; inner shell with thin radial by-spines.

The genus _Diplosphæra_ differs from its ancestral form _Leptosphæra_ in the development of radial by-spines on the surface of the inner shell, the outer shell being smooth.

Subgenus 1. _Diplosphærella_, Haeckel.

_Definition._--Radial main spines simple, without lateral branches.

1. _Diplosphæra hexagonalis_, n. sp. (Pl. 19, fig. 3).

Inner shell with regular, hexagonal meshes and very thin thread-like bars; at each nodal-point one bristle-shaped by-spine; outer shell twice as broad, with simple triangular meshes. Radial spines with three smooth edges. (The radially striped central capsule, enclosed in the inner shell, envelops a large central nucleus one-third its size, fig. 3.)

_Dimensions._--Diameter of the outer shell 0.36, inner 0.18.

_Habitat._--Central Pacific, Stations 265 to 274, surface.

2. _Diplosphæra ornata_, n. sp.

Inner shell with regular, hexagonal meshes, four times as broad as the bars; outer shell three times as broad, with simple triangular meshes. Radial main spines as well as the bars of both {247}shells very elegantly denticulated; radial by-spines (very numerous in the surface of the inner shell) smooth.

_Dimensions._--Diameter of the outer shell 0.7, inner 0.24.

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

3. _Diplosphæra dictyota_, n. sp.

Inner shell with regular, hexagonal meshes, six times as broad as the bars; at each nodal-point one radial by-spine; outer shell two and a half times as broad, with very delicate square meshes, separated by thread-like bars which arise from the sides of the triangular main meshes. Radial main spines with three serrated edges. (Differs from the similar _Diplosphæra gracilis_ in the simple main spines, with delicate dentition of the edges.)

_Dimensions._--Diameter of the outer shell 0.5, inner 0.2.

_Habitat._--North Atlantic, Canary Islands, surface.

4. _Diplosphæra polygonalis_, n. sp.

Inner shell with irregular, polygonal meshes and very thin thread-like bars, covered with very numerous bristle-shaped by-spines; outer shell twice as broad, with simple triangular meshes. Radial main spines with three smooth edges.

_Dimensions._--Diameter of the outer shell 0.44, inner 0.22.

_Habitat._--South Pacific, Station 288, surface.

Subgenus 2. _Diplosphæromma_, Haeckel.

_Definition._--Radial main spines with three rows of lateral branches (one row on each edge).

5. _Diplosphæra gracilis_, Haeckel.

_Diplosphæra gracilis_, Haeckel, 1862, Monogr. d. Radiol., p. 354, Taf.
x. fig. 1.

Inner shell with regular, hexagonal meshes and very thin bars; at each nodal-point one simple bristle-shaped radial by-spine; outer shell twice as broad, with very delicate square meshes, separated by thread-like bars which arise from the sides of the triangular main meshes. Radial spines with smooth edges and with three rows of simple curved lateral branches (four to six branches on each edge).

_Dimensions._--Diameter of the outer shell 0.54, inner 0.27.

_Habitat._--Mediterranean (Messina).

6. _Diplosphæra denticulata_, n. sp.

Inner shell with regular, hexagonal meshes, four times as broad as the bars; at each nodal-point is a simple bristle-shaped by-spine; outer shell three times as broad, with simple triangular meshes. {248}Radial spines very strong, with dentated edges and with three rows of lateral branches (six dentated curved branches on each edge).

_Dimensions._--Diameter of the outer shell 0.4, inner 0.13.

_Habitat._--North Atlantic, Azores, surface.

7. _Diplosphæra reticulata_, n. sp.

Inner shell with regular, hexagonal meshes, five times as broad as the bars, which are densely covered with very numerous, simple bristle-shaped by-spines; outer shell four times as broad, with very numerous small irregular polygonal meshes, forming a very delicate network, and filling out the large triangular main meshes. Radial spines with three serrated edges and three rows of short curved branches (four to five branches on each edge).

_Dimensions._--Diameter of the outer shell 0.6, inner 0.15.

_Habitat._--North Atlantic, Gulf Stream, Færöe Channel, surface, John Murray.

8. _Diplosphæra triglochin_, n. sp.

Inner shell with irregular, polygonal meshes and very thin thread-like bars; outer shell three times as broad, with similar irregular polygonal meshes, filling out the large triangular main meshes. Radial spines with three serrated edges, each of which bears one single large lateral branch, concavely curved towards the distal end. By-spines of the inner shell very numerous.

_Dimensions._--Diameter of the outer shell 0.5, inner 0.17.

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

Genus 99. _Drymosphæra_,[134] Haeckel, 1881, Prodromus, p. 452.

_Definition._--#Astrosphærida# with two extracapsular cortical shells, connected by long prismatic, radial spines; outer shell with thin radial by-spines.

The genus _Drymosphæra_ differs from its ancestral form _Leptosphæra_ in the development of radial by-spines on the surface of the outer shell, the inner shell being smooth.

Subgenus 1. _Drymosphærella_, Haeckel.

_Definition._--Radial by-spines simple, not branched (main spines simple).

1. _Drymosphæra hexagonalis_, n. sp.

Inner shell with regular, hexagonal meshes and very thin thread-like bars; outer shell twice as broad, with simple triangular meshes and thin thread-like bars, which bear very numerous, {249}bristle-shaped radial by-spines. Radial main spines with three smooth edges. (Differs from the first species of the other three genera of Diplosphærida in the presence of by-spines on the outer, and their absence on the inner shell.)

_Dimensions._--Diameter of the outer shell 0.32, inner 0.16.

_Habitat._--Central Pacific, Station 274, surface.

2. _Drymosphæra polygonalis_, n. sp. (Pl. 19, fig. 1).

_Diplosphæra polygonalis_, Haeckel, 1879, Atlas.

Inner shell with irregular, polygonal meshes and very thin thread-like bars; outer shell one and a half times as broad, with simple triangular meshes and thicker bars, which bear numerous bristle-shaped radial by-spines (in the figure the majority of these are broken off). Radial main spines with three smooth edges. (Similar to _Leptosphæra polygonalis_ and _Diplosphæra polygonalis_, but differs from both in the presence of by-spines on the outer, and their absence on the inner shell.)

_Dimensions._--Diameter of the outer shell 0.33, inner 0.22.

_Habitat._--North Pacific, Station 236 south of Japan, surface.

Subgenus 2. _Drymosphæromma_, Haeckel.

_Definition._--Radial by-spines forked or branched (main spines simple).

3. _Drymosphæra furcata_, n. sp.

Inner shell with irregular, polygonal meshes and thin bars, the former five times as broad as the latter; outer shell two and a half times as broad, with simple triangular meshes and smooth bars, bearing numerous long smooth bristle-shaped by-spines, which in the distal half are forked. Radial main spines with three smooth edges.

_Dimensions._--Diameter of the outer shell 0.4, inner 0.16.

_Habitat._--Indian Ocean, Ceylon, surface, Haeckel.

4. _Drymosphæra cladophora_, n. sp.

Inner shell with irregular, polygonal meshes, three to six times as broad as the smooth bars; outer shell twice as broad, with simple triangular meshes and very thin smooth bars, bearing numerous curved, irregularly branched, smooth by-spines. Radial main spines with three serrated edges.

_Dimensions._--Diameter of the outer shell 0.4, inner 0.2.

_Habitat._--Central Pacific, Station 276, surface.

5. _Drymosphæra dendrophora_, n. sp. (Pl. 20, figs. 1, 1_a_, 1_b_).

Inner shell with irregular, polygonal meshes and very thin thread-like bars; outer shell one and a half times as broad, with simple triangular meshes and thicker bars, which bear a forest of {250}very numerous, repeatedly dichotomous or irregularly branched, curved by-spines, longer than the diameter of the outer shell. Radial main spines with three dentated edges. All parts of the skeleton, the net bars as well as the radial beams and spines, are very elegantly denticulated (fig. 1_b_). The central capsule (fig. 1_a_) completely distends the inner shell and forces out protuberances through all its pores; in its centre lies a nucleus one-third its size.

_Dimensions._--Diameter of the outer shell 0.25, inner 0.16.

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

Genus 100. _Astrosphæra_,[135] n. gen.

_Definition._--#Astrosphærida# with two extracapsular cortical shells, connected by long, prismatic, radial spines; inner and outer shell with thin radial by-spines.

The genus _Astrosphæra_ differs from its ancestral form, _Leptosphæra_, in the development of radial by-spines on the surface of both shells.

Subgenus 1. _Astrosphærella_, Haeckel.

_Definition._--Radial main spines simple without lateral branches.

1. _Astrosphæra hexagonalis_, n. sp. (Pl. 19, fig. 4).

Inner shell with regular, hexagonal meshes and very thin bars, having a bristle-shaped, short radial by-spine in each hexagon-corner; outer shell twice as broad, with simple triangular meshes and thicker bars, bearing one row of simple bristle-shaped, curved, radial by-spines. Radial main spines with three smooth edges.

_Dimensions._--Diameter of the outer shell 0.32, inner 0.16.

_Habitat._--South Pacific (West Patagonia), Station 302, surface.

2. _Astrosphæra splendens_, n. sp.

Inner shell with regular, hexagonal meshes, four times as broad as the bars, and covered with numerous curved, long, bristle-shaped by-spines; outer shell three times as broad, with simple triangular meshes and thin bars, bearing a row of very long, curved, bristle-shaped by-spines. Radial main spines with three dentated edges. All parts of the skeleton elegantly denticulated, as in _Drymosphæra dendrophora_ (Pl. 20, fig. 1).

_Dimensions._--Diameter of outer shell 0.7, inner 0.24.

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

{251}Subgenus 2. _Astrosphæromma_.

_Definition._--Radial main spines with three rows of lateral branches (one row on each edge).

3. _Astrosphæra sideræa_, n. sp.

Inner shell with regular, hexagonal meshes, six times as broad as the bars, and covered with numerous short bristle-shaped by-spines; outer shell four times as broad, with simple triangular meshes, and rows of long bristle-shaped by-spines arising from the bars. Radial main spines with three serrated edges and three rows of lateral branches (four branches on each edge).

_Dimensions._--Diameter of the outer shell 0.6, inner 0.15.

_Habitat._--Central Pacific, Station 266, surface.

4. _Astrosphæra stellata_, n. sp. (Pl. 19, fig. 5).

_Diplosphæra stellata_, Haeckel, 1881, Prodrom. et Atlas.

Inner shell with regular, hexagonal, six-rayed meshes, each bar being crossed by a transverse tangential rod, at each nodal-point a long bristle-shaped by-spine; outer shell three times as broad, with simple triangular meshes and denticulated thin bars, bearing a row of bristle-shaped radial by-spines. Radial main spines in the proximal half with three serrated edges, in the distal half with three rows of curved lateral branches (five branches on each edge).

_Dimensions._--Diameter of the outer shell 0.6, inner 0.2.

_Habitat._--Central Pacific, Station 274, surface.

Subfamily ACTINOMMIDA,[136] Haeckel, 1862, Monogr. d. Radiol., p. 440 (_sensu emendato_).

_Definition._--#Astrosphærida# with three concentric, spherical, lattice-shells, united by radial beams.

Genus 101. _Actinomma_,[137] Haeckel, 1862, Monogr. d. Radiol., p. 440.

_Definition._--#Astrosphærida# with three concentric lattice-spheres and numerous simple radial spines of one kind.

The genus _Actinomma_ is here restricted to those #Sphæroidea# which combine the possession of three concentric lattice-shells with numerous radial spines on the surface; the spines are all simple, being of one and the same kind. Commonly two of the three shells are intracapsular medullary shells, connected by radial beams (piercing {252}the central capsule) with the outer, extracapsular, cortical shell. But in some species only one medullary shell is enclosed in the central capsule, whilst both other shells lie outside it. In such case the distance between these two cortical shells is much smaller than their distance from the simple internal medullary shell. These forms correspond more to aculeate _Rhodosphæræ_, whilst the others resemble aculeate _Thecosphæræ_.

Subgenus 1. _Actinommantha_, Haeckel.

_Definition._--Pores of the cortical shell regular, of nearly equal size and similar form; spines on the entire surface (commonly one spine at each nodal-point).

1. _Actinomma hexagonium_, n. sp.

Cortical shell, as well as both medullary shells, very thin walled, with regular, hexagonal pores and thread-like bars between them. Pores of the outer shell twice as broad as those of the middle, and three times as broad as those of the inner shells. Radial proportion of the three spheres = 1 : 3 : 9; about twenty thin radial beams between them. At each nodal-point of the surface arises one bristle-shaped radial spine, half as long as the radius.

_Dimensions._--Diameter of the outer shell 0.22, middle 0.07, inner 0.025; meshes of the cortical shell 0.01; length of the spines 0.05.

_Habitat._--Central Pacific, Stations 270 to 274, surface.

2. _Actinomma facetum_, n. sp.

Cortical shell thick walled, with regular, circular, hexagonally framed pores, three times as broad as the bars. Pores of both medullary shells regular, circular. Radial proportion of the three spheres = 1 : 2 : 4; about forty thin radial beams between them. At each nodal-point of the surface arises one short, three-sided pyramidal, radial spine, about one-third as long as the radius.

_Dimensions._--Diameter of the outer shell 0.16, middle 0.08, inner 0.04; cortical pores 0.012, bars 0.004; length of the spines 0.03, basal breadth 0.015.

_Habitat._--North Pacific, Station 253, depth 3125 fathoms.

3. _Actinomma anthomma_, n. sp.

Cortical shell thick walled, with regular, six-lobed pores, twice as broad as the bars. At each nodal-point of the surface is one short conical radial spine, as long as the diameter of the pores; one corresponding to each lobe, and there is therefore around each pore a regular corona of six spines, as in _Haliomma lirianthus_ (Pl. 28, fig. 1_b_). Both medullary shells with simple, circular, regular pores. Radial proportion of the three spheres = 1 : 2.5 : 7; radial beams between them only six, opposite in pairs in the three dimensive axes.

{253}_Dimensions._--Diameter of the outer shell 0.2, middle 0.075, inner 0.003; cortical pores 0.01, bars 0.005; length of the spines 0.01.

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

4. _Actinomma castanomma_, n. sp.

Cortical shell as well as both medullary shells thick walled, with regular, circular pores, twice as broad as the bars; between them at each nodal-point one bristle-shaped radial spine, one-third as long as the radius, with conical base. Radial proportion of the three spheres = 2 : 3 : 8; only six radial beams between them (opposed in pairs in the three dimensive axes).

_Dimensions._--Diameter of the outer shell 0.15, middle 0.06, inner 0.04; cortical pores 0.008, bars 0.004; length of the spines 0.025.

_Habitat._--South Atlantic, Station 333, surface.

5. _Actinomma entactinia_, Stöhr.

_Actinomma entactinia_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 93, Taf.
ii. fig. 12.

Cortical shell as well as both medullary shells thick walled, with regular, circular pores, of the same breadth as the bars. Radial proportion of the three spheres = 1 : 3 : 8; radial beams between them very numerous (thirty to fifty or more?). Entire surface covered with short thick conical spines, only one-fifth as long as the radius.

_Dimensions._--Diameter of the outer shell 0.16, middle 0.06, inner 0.02; cortical pores and bars 0.007; length of the spines 0.015.

_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Caltanisetta.

Subgenus 2. _Actinommetta_, Haeckel.

_Definition._--Pores of the outer shell regular, of nearly equal size and similar form; spines not over the entire surface, but scattered at intervals (their number smaller than that of the nodal-points).

6. _Actinomma japonicum_, n. sp.

Cortical shell thick walled, with regular, circular, hexagonally framed pores, three times as broad as the bars. Both medullary shells with simple, circular, regular pores, of the same breadth as the bars. Radial proportion of the three spheres = 2 : 5 : 9; radial beams between them twenty, prolonged outside into twenty symmetrically disposed, three-sided pyramidal spines, as long as the radius.

_Dimensions._--Diameter of the outer shell 0.18, middle 0.1, inner 0.04; cortical pores 0.01, bars 0.003; length of the spines 0.1, basal breadth 0.012.

_Habitat._--North Pacific, Station 240, east of Japan, surface.

{254}7. _Actinomma denticulatum_, n. sp. (Pl. 29, fig. 3).

Cortical shell thick walled, with regular, circular, double-edged pores, twice as broad as the bars. Forty to fifty radial spines, three-sided pyramidal, half as long as the radius, with three elegantly denticulated edges. Radial proportion of the three spheres = 1 : 2 : 5. (Differs from _Haliomma denticulatum_ only in the double medullary shell and larger size.)

_Dimensions._--Diameter of the outer shell 0.14, middle 0.06, inner 0.03; cortical pores 0.01, bars 0.005; length of the spines 0.04, basal breadth 0.01.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.

8. _Actinomma trinacrium_, Haeckel.

_Actinomma trinacrium_, Haeckel, 1862, Monogr. d. Radiol., p. 441, Taf.
xxiv. figs. 6-8.

_Haliomma trinacrium_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 815.

Cortical shell as well as both medullary shells thin walled, with subregular, circular pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 3 : 9; radial beams between them twenty, prolonged outside into strong, three-sided pyramidal spines, as long as the radius; between them, on the surface, numerous similar spines. Sometimes the latter remain smaller, the pores more irregular, and then this species corresponds to _Echinomma trinacrium_.

_Dimensions._--Diameter of the outer shell 0.09, middle 0.03, inner 0.01; cortical pores 0.008, bars 0.004; length of the spines 0.04, basal breadth 0.01.

_Habitat._--Mediterranean (Messina, Corfu, Haeckel), surface.

9. _Actinomma pachyderma_, n. sp. (Pl. 29, figs. 4, 5).

Cortical shell very thick walled, with regular, circular, double-edged pores, twice as broad as the bars. Both medullary shells with simple, small, circular pores, of the same breadth as the bars. Radial proportion of the three spheres = 1 : 2 : 4; radial spines about twenty, conical, shorter than the radius, prolonged inside into twenty very thin connecting beams (fig. 4).

_Dimensions._--Diameter of the outer shell 0.08, middle 0.04, inner 0.02; cortical pores 0.01; bars 0.005; length of the spines 0.03, basal breadth 0.01.

_Habitat._--South Pacific, Station 297, depth 1775 fathoms.

Subgenus 3. _Actinommilla_, Haeckel.

_Definition._--Pores of the cortical shell irregular, of different size and form; spines over the entire surface (commonly one spine at each nodal-point).

10. _Actinomma spinigerum_, Stöhr.

_Actinomma spinigerum_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 92, Taf.
ii. fig. 10.

Cortical shell thick walled, with irregular, roundish, or subcircular pores, twice to four times as broad as the bars. Radial proportion of the three spheres = 1 : 3 : 8; between them eight (?) {255}connecting radial beams. Entire surface densely covered with small conical spines, not larger than the pores.

_Dimensions._--Diameter of the outer shell 0.17, middle 0.07, inner 0.023; cortical pores 0.006 to 0.012, bars 0.003; length of the spines 0.01.

_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

11. _Actinomma hirsutum_, n. sp.

Cortical shell thick walled, with irregular, roundish pores, about the same breadth as the bars. Radial proportion of the three spheres = 1 : 2 : 8; between them numerous (twenty to thirty or more) cylindrical connecting beams. Entire surface densely covered with innumerable small bristle-shaped spines, as long as the diameter of the inner shell.

_Dimensions._--Diameter of the outer shell 0.25, middle 0.06, inner 0.03; cortical pores and bars 0.004 to 0.008; length of the spines 0.03.

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

Subgenus 4. _Actinommura_, Haeckel.

_Definition._--Pores of the cortical shell irregular, of different size and form; spines not over the entire surface, but scattered at intervals (their number smaller than that of the nodal-points).

12. _Actinomma capillaceum_, n. sp. (Pl. 29, fig. 6).

Cortical shell very thin walled, with irregular, polygonal meshes (sixteen to eighteen on the radius), three to six times as broad as the bars. Both medullary shells with smaller pores of the same structure. Radial proportion of the three spheres = 1 : 2.5 : 7; radial connecting beams between them very thin and numerous (one hundred and twenty to one hundred and fifty or more), each prolonged outside into a short three-sided pyramidal spine, as long as the radius of the inner shell. (Similar to _Haliomma capillaceum_.)

_Dimensions._--Diameter of the outer shell 0.27, middle 0.1, inner 0.04; cortical pores 0.01 to 0.02, bars 0.003; length of the spines 0.02, basal breadth 0.005.

_Habitat._--Central Pacific, Stations 266 to 274, surface.

13. _Actinomma arcadophorum_, n. sp. (Pl. 29, figs. 7, 8).

Cortical shell very thin walled, with irregular, polygonal meshes, ten to twenty times as broad as the bars; twelve to sixteen on the radius. Both medullary shells with similar delicate network. Radial proportion of the three spheres = 1 : 2 : 6; numerous thin radial beams (forty to eighty or more) connect both medullary shells and alternate with other beams, which arise from arcade-shaped {256}protuberances of the outer medullary shell, and connect it with the cortical shell. Outer prolongations of these form the bristle-shaped spines of the surface.

_Dimensions._--Diameter of the outer shell 0.22, middle 0.09, inner 0.04; cortical pores 0.01 to 0.02, bars 0.001 to 0.002; length of the radial spines 0.2.

_Habitat._--Central Pacific, Station 266, surface.

14. _Actinomma schwageri_, Stöhr.

_Actinomma schwageri_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 92, Taf.
ii. fig. 9_a_, _b_.

Cortical shell thick walled, with irregular, large, polygonal meshes, five to twelve times as broad as the bars; six to eight on the radius. Both medullary shells with very small, circular, regular pores. Radial proportion of the three spheres = 1 : 2 : 9; connecting radial beams between them nine, prolonged outside into nine short stout, three-sided pyramidal spines, as long as the diameter of the inner shell.

_Dimensions._--Diameter of the outer shell 0.17, middle 0.04, inner 0.02; cortical pores 0.01 to 0.03, bars 0.006 and less; length of the spines 0.02, basal breadth 0.01.

_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

15. _Actinomma dodecomma_, n. sp.

Cortical shell thin walled, with irregular, roundish pores, three to six times as broad as the bars. Both medullary shells with regular, circular pores, twice as broad as the bars. Radial proportion of the three shells = 1 : 2.5 : 7; connecting radial beams between them twelve, regularly disposed, prolonged outside into twelve strong, three-sided pyramidal spines, as long as the radius.

_Dimensions._--Diameter of the outer shell 0.14, middle 0.05, inner 0.02; cortical pores 0.008 to 0.018, bars 0.003; length of the spines 0.08, breadth 0.02.

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

16. _Actinomma pachycapsa_, n. sp.

Cortical shell very thick walled, with irregular, roundish pores, twice to four times as broad as the bars; twelve to sixteen on the radius. Radial proportion of the three spheres = 1 : 3 : 12. Both medullary shells of similar irregular structure, connected with the cortical shell by twelve regularly disposed radial beams, which are prolonged outside into twelve short stout conical spines, as long as the diameter of the middle shell.

_Dimensions._--Diameter of the outer shell 0.25, middle 0.06, inner 0.02; cortical pores 0.006 to 0.012, bars 0.003; length of the spines 0.05, breadth 0.02.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

17. _Actinomma giganteum_, n. sp.

Cortical shell thick walled, little larger than the outer medullary shell, whilst the inner is only one-tenth as large. Pores of all three shells irregular, roundish, or subcircular, twice to three times {257}as broad as the bars, on an average twice as large in the outer and middle as in the inner shell. Sixty to eighty short conical radial spines on the surface, about as long as the diameter of the inner shell, and one-fourth as broad at the base. Radial proportion of the three spheres = 1 : 9 : 10.

_Dimensions._--Diameter of the outer shell 0.4 to 0.5, middle 0.35 to 0.45, inner 0.05 to 0.06.

_Habitat._--Fossil in Barbados.

Genus 102. _Echinomma_,[138] Haeckel, 1881, Prodromus, p. 453.

_Definition._--#Astrosphærida# with three concentric lattice-spheres and numerous simple radial spines of two different kinds; larger main spines and smaller by-spines.

The genus _Echinomma_, differs from its ancestral form, _Actinomma_, in the differentiation of the radial spines. Whilst a large number of small by-spines cover the entire surface, a smaller number of large main spines are scattered over it, or limited to certain regularly distributed points. It represents _Heliosoma_ among the Haliommida.

Subgenus 1. _Echinommetta_, Haeckel.

_Definition._--Pores of the cortical shell regular, of nearly equal size and similar form.

1. _Echinomma echinidium_, n. sp.

Cortical shell thin walled, with regular, hexagonal pores, four times as broad as the bars; ten to twelve on the radius. Both medullary shells with regular, circular pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 5. Surface covered with short bristle-shaped by-spines (one in every hexagon-corner); twenty main spines regularly disposed, three-sided pyramidal, as long as the diameter of the inner shell.

_Dimensions._--Diameter of the outer shell 0.1, middle 0.045, inner 0.02; cortical pores 0.008, bars 0.002; length of the main spines 0.02, breadth 0.01.

_Habitat._--South Pacific, Station 295, surface.

2. _Echinomma cidaris_, n. sp.

Cortical shell thin walled, with regular, circular, hexagonally framed pores, twice as broad as the bars; six to eight on the radius. Both medullary shells with simple, circular pores. Radial proportion of the three spheres = 1 : 2 : 6. Surface covered with short bristle-shaped by-spines, half as long as the forty to fifty main spines, which are three-sided pyramidal, and reach the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.18, middle 0.06, inner 0.03; cortical pores 0.01, bars 0.005; length of the main spines 0.08, basal breadth 0.015.

_Habitat._--Central Pacific, Station 272, surface.

{258}3. _Echinomma aculeatum_, Haeckel.

_Actinomma aculeatum_, Stöhr, 1880 Palæontogr., vol. xxvi. p. 92, Taf.
ii. fig. 11.

Cortical shell thick walled with regular circular pores, of the same breadth as the bars; eight to ten on the radius. Radial proportion of the three spheres = 1 : 2 : 8. Surface covered with short conical by-spines about twenty strong main spines, three-sided pyramidal, one-third as long as the shell diameter.

_Dimensions._--Diameter of the outer shell 0.16, middle 0.04, inner 0.02; cortical pores and bars 0.003; length of the main spines 0.05, basal breadth 0.013.

_Habitat._--Fossil in the Tertiary rocks of Sicily and Barbados; living in the Atlantic, Station 332, depth 2200 fathoms.

4. _Echinomma diadema_, n. sp.

Cortical shell thick walled with regular circular pores, twice as broad as the bars; sixteen to eighteen on the radius. Radial proportion of the three spheres = 1 : 3 : 11. Surface covered with short bristle-shaped by-spines one third as long as the twelve stout conical main spines, which reach in length the radius, and lie opposite in pairs in six axes.

_Dimensions._--Diameter of the outer shell 0.22, middle 0.06, inner 0.02; cortical pores 0.006, bars 0.003 length of the main spines 0.12, basal breadth 0.02.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

Subgenus 2. _Echinommura_, Haeckel.

_Definition._--Pores of the cortical shell irregular, of different size or form.

5. _Echinomma sphærechinus_, n. sp. (Pl. 29, fig. 2).

_Actinomma sphærechinus_, Haeckel, 1879, Atlas (pl. xxix. fig. 2).

Cortical shell thin walled, with irregular, roundish pores, twice to five times as broad as the bars; five to seven on the radius. Both medullary shells with regular, circular pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 4. Surface covered with thirty to fifty pyramidal main spines, as long as the diameter of the inner shell, and with numerous small conical by-spines of half the length.

_Dimensions._--Diameter of the outer shell 0.11, middle 0.05, inner 0.025; cortical pores 0.01 to 0.02, bars 0.004; length of the main spines 0.03, basal breadth 0.005.

_Habitat._--North Atlantic, Station 353, surface.

6. _Echinomma trinacrium_, Haeckel.

_Actinomma trinacrium_, Haeckel, 1862, Monogr. d. Radiol., p. 441, Taf.
xxiv. figs. 6-8.

Cortical shell thin walled, with irregular, roundish pores, twice to three times as broad as the bars. Both medullary shells with regular, circular pores. Radial proportion of the three spheres {259}= 1 : 3 : 9. On the surface about twenty three-sided pyramidal main spines, as long as the radius, and numerous (forty to sixty) by-spines of half the length. (Compare with this species _Actinomma trinacrium_, with which it is connected by transitional forms.)

_Dimensions._--Diameter of the outer shell 0.09, middle 0.03, inner 0.01; cortical pores 0.008 to 0.012, bars 0.004; length of the spines 0.02 to 0.05, basal breadth 0.01.

_Habitat._--Mediterranean (Messina).

7. _Echinomma toxopneustes_, n. sp. (Pl. 29, fig. 1).

Cortical shell thin walled, with large, irregular roundish, polygonally framed pores, twice to four times as broad as the crested bars. Both medullary shells of similar structure. Radial proportion of the three spheres = 1 : 2.5 : 6. Numerous (thirty to fifty or more) thin radial beams connecting them, prolonged outside into strong three-sided pyramidal spines, shorter than the radius; each of the three wings with two teeth. Between these, numerous smaller angular by-spines of one-quarter to one-half the length.

_Dimensions._--Diameter of the outer shell 0.12, middle 0.05, inner 0.02; cortical pores 0.01 to 0.03, bars 0.008; length of the main spines 0.05, basal breadth 0.01.

_Habitat._--South-east Pacific (South of Juan Fernandez), Station 300, surface.

Genus 103. _Pityomma_,[139] Haeckel, 1881, Prodromus, p. 453.

_Definition._--#Astrosphærida# with three concentric lattice-shells and numerous branched radial spines.

The genus _Pityomma_ differs from its ancestral form, _Actinomma_, in the ramification of its radial spines, and exhibits therefore the same relation to it that _Elatomma_, among the Haliommida, bears to _Haliomma_.

1. _Pityomma scoparium_, n. sp.

Cortical shell thick walled, connected with both concentric medullary shells by twenty thin radial beams, which are prolonged outside into twenty large cylindrical radial spines; these are somewhat shorter than the shell radius, simple in the proximal inner half, irregularly branched in the outer half. All three spheres with regular, circular pores, twice to three times as broad as the bars; radial proportion = 1 : 2 : 6. (Similar to _Cladococcus scoparius_, Pl. 27, fig. 2, and _Elatomma scoparium_, but differs from both in the double medullary shell.)

_Dimensions._--Diameter of the outer shell 0.15, middle 0.05, inner 0.025; length of the spines 0.1.

_Habitat._--Central Pacific, Station 273, surface.

{260}2. _Pityomma piniferum_, n. sp.

Cortical shell thin walled, with irregular, roundish pores, connected with both medullary shells by twenty stout radial beams, which are prolonged outside into twenty large three-sided prismatic spines. These are longer than the shell diameter and have three dentate edges, being branched like a pine tree (with four to six ramified branches on each edge, decreasing in size towards the distal end); similar to those of _Cladococcus abietinus_ (Pl. 27, fig. 3). Radial proportion of the three spheres = 1 : 2 : 8. Both medullary shells with regular, circular pores, twice as broad as the bars.

_Dimensions._--Diameter of the outer shell 0.2, middle 0.05, inner 0.025; length of the spines 0.25.

_Habitat._--South Pacific, Station 299 (Juan Fernandez), surface.

3. _Pityomma drymodes_, n. sp. (Pl. 29, fig. 9).

Cortical shell thin walled, connected with both medullary shells by very numerous (one hundred to two hundred or more) very thin radial beams, which are prolonged outside into thin branched radial spines, scarcely half as long as the shell radius, each spine bearing six to nine simple branches. Outer and middle shell uneven, with hill-shaped protuberances and valleys between them; the connecting radial beams, which arise from the top of the protuberances of the middle shell, are inserted into the deepest part of the valleys of the outer shell. Radial proportion of the three spheres = 1 : 3 : 8. Outer medullary shell with small, irregular, roundish, or polygonal pores, not much broader than the bars; innermost shell with polygonal pores and very thin bars.

_Dimensions._--Diameter of the outer shell 0.28, middle 0.1, inner 0.033; length of the spines 0.07, breadth 0.004.

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

Subfamily CROMYOMMIDA,[140] Haeckel, 1881, Prodromus, pp. 449, 453.

_Definition._--#Astrosphærida# with four concentric spherical lattice-shells.

Genus 104. _Cromyomma_,[141] Haeckel, 1881, Prodromus, p. 454.

_Definition._--#Astrosphærida# with four concentric lattice-spheres and numerous simple radial spines of one kind.

The genus _Cromyomma_ is the common ancestral form of the Cromyommida, or of those Astrosphærida in which the shell is composed of four concentric spheres, connected by radial beams. Usually two of these are intracapsular or medullary {261}shells, two extracapsular or cortical shells; the distance between the former and the latter is greater than the distance between either the two inner or the two outer shells. In some cases, however (_e.g._, _Cromyomma zonaster_), the distance between all four shells is equal.

Subgenus 1. _Cromyommetta_, Haeckel.

_Definition._--Pores of the outer cortical shell regular, of nearly equal size and similar form.

1. _Cromyomma villosum_, n. sp. (Pl. 30, fig. 2).

Radial proportion of the four spheres = 1 : 2 : 4 : 5. Outer cortical shell thick walled, densely covered with innumerable bristle-shaped radial spines, half as long as the radius. Pores regular, circular, double-edged, of the same breadth as the bars; ten to twelve on the radius. The thick outer shell is so dark, that the outlines only of the other three shells can be seen.

_Dimensions._--Diameter of the four shells--(A) outer cortical shell 0.2, (B) inner cortical shell 0.16, (C) outer medullary shell 0.08, (D) inner medullary shell 0.04; pores and bars of the outer shell 0.008; length of the spines 0.04.

_Habitat._--Central Pacific, Station 267, depth 2700 fathoms.

2. _Cromyomma zonaster_, Haeckel.

_Acanthosphæra zonaster_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 285, Taf. ii. fig. 2.

Radial proportion of the four spheres = 2 : 3 : 4 : 5. Outer cortical shell thick walled, densely covered with numerous bristle-shaped radial spines, as long as the radius. Pores regular, circular, twice as broad as the bars; eight to ten on the radius. The thick outer shell is so dark, that the outlines only of the other three shells can be seen.

_Dimensions._--Diameter of the four shells--(A) 0.15, (B) 0.12, (C) 0.09, (D) 0.06; pores of the outer shell 0.01, bars 0.005; length of the spines 0.08.

_Habitat._--Arctic Ocean, Greenland (depth 1000 fathoms), "Alert" Expedition.

3. _Cromyomma perplexum_, Stöhr.

_Cromyomma perplexum_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 95, Taf.
iii. fig. 5.

Radial proportion of the four spheres = 1 : 2 : 3 : 4. Outer cortical shell thick walled, densely covered with short conical spines, as long as the diameter of the pores. These are regular, circular, three times as broad as the bars; six to eight on the radius. The thick outer shell is so dark, that the outlines only of the three other shells can be seen.

_Dimensions._--Diameter of the four shells--(A) 0.17, (B) 0.13, (C) 0.087, (D) 0.043; pores of the outer shell 0.015, bars 0.005; length of the spines 0.02.

_Habitat._--Fossil in the Tertiary rocks of Sicily (Grotte) Stöhr.

{262}Subgenus 2. _Cromyommura_, Haeckel.

_Definition._--Pores of the outer cortical shell irregular, of different size and form.

4. _Cromyomma perspicuum_, n. sp. (Pl. 30, fig. 8).

_Cromyosphæra perspicua_, Haeckel, 1879, Atlas (pl. xxx. fig. 8).

Radial proportion of the four shells = 1 : 2.5 : 6 : 9. Outer cortical shell very thin walled, with thread-like bars, and irregular, polygonal pores; inner cortical shell with similar pores, but with thicker bars. Both medullary shells with regular, circular pores (the outer three times as broad as the inner). Numerous thin radial beams connect the latter with the former; other very thin and numerous beams connect the two cortical shells, and are prolonged outside into short bristle-shaped spines (often longer than in the figure).

_Dimensions._--Diameter of the four shells--(A) 0.18, (B) 0.12, (C) 0.05, (D) 0.02; pores of the outer shell 0.01 to 0.02; length of the spines 0.01 to 0.03.

_Habitat._--Central Pacific, Station 274, surface.

5. _Cromyomma quadruplex_, Haeckel.

_Cromyomma quadruplex_, Haeckel, 1862, Monogr. d. Radiol., p. 446.

_Haliomma quadruplex_, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 243.

Radial proportion of the four spheres = 1 : 3 : 7 : 10. Outer cortical shell thin walled, irregularly covered with numerous angular spines, as long as the radius. Pores of all four shells irregular, roundish, increasing in size from the first to the fourth.

_Dimensions._--Diameter of the four shells--(A) 0.15, (B) 0.1, (C) 0.045, (D) 0.015; pores of the outer shell 0.01 to 0.02; length of the spines 0.07.

_Habitat._--North Atlantic, Station 353, depth 2965 fathoms.

6. _Cromyomma macroporum_, Stöhr.

_Cromyomma macroporum_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 95, Taf.
iii. fig. 4.

Radial proportion of the four spheres = 1 : 3 : 6 : 9. Outer cortical shell thick walled, densely covered with short conical spines, as long as the diameter of the pores; the latter are irregular, roundish, or polygonal, larger and smaller alternating.

_Dimensions._--Diameter of the four shells--(A) 0.1, (B) 0.066, (C) 0.033, (D) 0.011; pores of the outer shell 0.033 to 0.016, bars 0.003; length of the spines 0.01.

_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.

7. _Cromyomma circumtextum_, n. sp. (Pl. 30, fig. 4).

Radial proportion of the four spheres = 1 : 2 : 5 : 7. Outer cortical shell very delicate and thin walled, with thread-like bars and large, irregular, polygonal meshes (larger than the innermost shell); {263}inner cortical shell also with irregular, polygonal pores, three to nine times as broad as the thick bars. Both medullary shells with subregular, circular pores (the outer three times as broad as the inner). Radial spines twelve to twenty, three-sided prismatic, stout, piercing the three outer shells, inserted on the innermost; their outer part pyramidal, half as long as the radius.

_Dimensions._--Diameter of the four shells--(A) 0.22, (B) 0.15, (C) 0.07, (D) 0.03; meshes of the outer shell 0.02 to 0.04; length of the outer spines 0.05.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.

8. _Cromyomma mucronatum_, n. sp. (Pl. 30, figs. 5, 5_a_).

Radial proportion of the three spheres = 1 : 2 : 3 : 6. Outer cortical shell thin walled, with large, irregular, roundish pores and crested three-sided bars; inner cortical shell with regular, circular, hexagonally formed pores (four times as broad as the bars). Both medullary shells with simple, small, regular, circular pores (fig. 5_a_). Twelve radial spines three-sided prismatic, dagger-shaped, with three teeth, as long as the diameter of the innermost shell.

_Dimensions._--Diameter of the four shells--(A) 0.24, (B) 0.12, (C) 0.08, (D) 0.04; meshes of the outer shell 0.02 to 0.04; length of the spines 0.04.

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

Genus 105. _Cromyechinus_,[142] Haeckel, 1881, Prodromus, p. 454.

_Definition._--#Astrosphærida# with four concentric lattice-spheres and numerous simple spines of two different kinds; larger main spines and smaller by-spines.

The genus _Cromyechinus_ differs from _Cromyomma_ in the same way as _Echinomma_ from _Actinomma_; the radial spines being differentiated into two different kinds; a larger number of small by-spines, and a smaller number of large main spines.

1. _Cromyechinus icosacanthus_, n. sp. (Pl. 30, fig. 1).

Radial proportion of the three spheres = 1 : 2 : 6 : 8. Outer cortical shell very delicate, with very small, regular, circular pores, covered with very numerous bristle-shaped by-spines, half as long as the radius; inner cortical shell with very large, irregular, polygonal pores, three to eight times as broad as the bars. Both medullary shells with regular, circular pores, connected with the former by twenty regularly disposed, very thin bars; these are prolonged outside into twenty very stout, three-sided prismatic main spines, as long as the radius, which arise from the inner cortical shell, and at the distal end are cuspidate.

_Dimensions._--Diameter of the four shells--(A) 0.16, (B) 0.13, (C) 0.04, (D) 0.02; pores of the outer cortical shell 0.003, of the inner 0.03, bars 0.003; length of the spines 0.08.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.

{264}2. _Cromyechinus dodecacanthus_, n. sp. (Pl. 30, figs. 3, 3_a_).

Radial proportion of the four spheres = 1 : 3 : 10 : 12. Outer cortical shell very delicate, with very small, regular, circular pores, covered with numerous short bristle-shaped by-spines, scarcely one-fourth as long as the radius; inner cortical shell with very large, irregular, polygonal pores, twice to six times as broad as the bars. Both medullary shells with very small, regular, circular pores, connected with the former by twelve regularly disposed, thin radial beams; these are prolonged outside into twelve strong, three-sided pyramidal main spines, one-third as long as the shell diameter. (Differs from the foregoing only in the number and form of the radial spines.)

_Dimensions._--Diameter of the four shells--(A) 0.12, (B) 0.1, (C) 0.03, (D) 0.01; pores of the outer cortical shell 0.002, of the inner 0.02, bars 0.002; length of the spines 0.04, basal breadth 0.01.

_Habitat._--South Atlantic, Station 325, surface.

3. _Cromyechinus polyacanthus_, n. sp.

Radial proportion of the four spheres = 1 : 2 : 8 : 10. Outer cortical shell of the same structure as the inner, with irregular, roundish pores, twice to six times as broad as the bars. Both medullary shells with small, regular, circular pores, twice as broad as the bars. Connecting radial beams forty to sixty, thin, cylindrical, prolonged outside into forty to sixty strong conical main spines, about as long as the radius. Between these, numerous thin bristle-shaped by-spines, nearly of the same length.

_Dimensions._--Diameter of the four shells--(A) 0.25, (B) 0.2, (C) 0.05, (D) 0.025; pores of both cortical shells 0.01 to 0.03; length of the spines 0.12.

_Habitat._--North Pacific, Station 237, surface.

Genus 106. _Cromyodrymus_,[143] Haeckel, 1881, Prodromus, p. 454.

_Definition._--#Astrosphærida# with four concentric lattice-spheres and numerous branched radial spines.

The genus _Cromyodrymus_ differs from its ancestral form, _Cromyomma_, in the ramification of the radial spines, and exhibits therefore the same relation to it that _Pityomma_ among the Actinommida bears to _Actinomma_.

1. _Cromyodrymus quadricuspis_, n. sp. (Pl. 30, figs. 7, 7_a_).

Radial proportion of the four shells = 1 : 3 : 6 : 12. All four shells with regular, circular pores, about twice as broad as the bars. Radial proportion of the pores in the four shells = 2 : 4 : 2 : 1. Radial spines fifty to sixty, three-sided prismatic, half as long as the radius, with three recurved teeth, each spine in this way bearing four points.

{265}_Dimensions._--Diameter of the four shells--(A) 0.16, (B) 0.08, (C) 0.04, (D) 0.013; length of the spines 0.03 to 0.04, breadth 0.007.

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

2. _Cromyodrymus abietinus_, n. sp. (Pl. 30, fig. 6).

Radial proportion of the four shells = 1 : 2 : 5 : 11. All four shells with irregular, roundish pores, twice to four times as broad as the bars. Radial proportion of the pores in the four shells = 9 : 3 : 2 : 1. Radial spines eighty to one hundred and twenty, about as long as the radius, branched like a pine tree, with six to twelve ramified branches.

_Dimensions._--Diameter of the four shells--(A) 0.22, (B) 0.1, (C) 0.04, (D) 0.02; length of the spines 0.12, breadth 0.006.

_Habitat._--South-east Pacific (Juan Fernandez), Station 299, surface.

Subfamily CARYOMMIDA,[144] Haeckel.

_Arachnosphærida_, Haeckel, 1862, Monogr. d. Radiol., p. 354; Prodromus, 1881, p. 454.

_Definition._--#Astrosphærida# with five or more concentric spherical lattice-shells.

Genus 107. _Caryomma_,[145] n. gen.

_Definition._--#Arachnosphærida# with five to six or more concentric spherical lattice-shells; two inner (intracapsular) medullary and three or more outer (extracapsular) cortical shells, composed of ordinary lattice-work; distance between the former and the latter greater than between any other two shells.

The genus _Caryomma_ may be regarded as a _Cromyomma_, in which the number of the cortical shells is increased to three, four, or more. These lie outside the central capsule, whilst two medullary shells lie within it, and are connected with the former by numerous radial spines piercing the wall of the capsule. The ordinary lattice-work is not arachnoidal, as in the three following genera.

1. _Caryomma regulare_, n. sp.

Radial proportion of the five shells = 1 : 2 : 6 : 8 : 10. All five shells with regular, circular pores, twice to three times as broad as the bars, and gradually increasing in size from the innermost to the outermost shell. Radial beams connecting them twenty, prolonged on the surface into twenty stout, three-sided pyramidal, radial spines, half as long as the radius, regularly disposed.

_Dimensions._--Diameter of the five shells--(A) 0.25, (B) 0.2, (C) 0.15, (D) 0.05, (E) 0.025.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.

{266}2. _Caryomma irregulare_, n. sp.

Radial proportion of the six shells = 1 : 2.5 : 8 : 10.5 : 13 : 15. Both inner (medullary) shells with regular, circular pores, the other four (cortical) shells with irregular, roundish pores, gradually increasing in size from the innermost to the outermost shell. Radial spines sixty to eighty, pyramidal, irregularly disposed.

_Dimensions._--Diameter of the six shells--(A) 0.3, (B) 0.26, (C) 0.21, (D) 0.16, (E) 0.05, (F) 0.02.

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

Genus 108. _Arachnopila_,[146] n. gen.

_Definition._--#Astrosphærida# with five to ten or more cortical, concentric, polyhedral, or spherical lattice-shells, composed of a very thin cobweb-like network; innermost shell with hexagonal (regular) or polygonal (irregular) meshes; other shells with simple triangular meshes, without diagonal threads between them.

The genus _Arachnopila_, together with the two following genera, forms the peculiar small group of large Arachnosphærida, separated from the true Caryommida by the totally different structure and disposition of the numerous concentric shells; the former exhibits a similar relation to the latter that the Diplosphærida bears to the Elatommida among the dispherical Haliommida. The concentric shells (five to ten or more) lie outside the central capsule, and are composed of very delicate, cobweb-like threads. From the innermost shell arise numerous, three-sided prismatic, very long spines, from which at equal regular distances arise lateral branches (three pairs from each spine, and one pair from each corner). In _Arachnopila_ these threads pass directly from one spine to the other, and form simple, large, triangular meshes between them. The concentric shells are not connected by interwoven diagonal threads.

1. _Arachnopila hexagonella_, n. sp.

Innermost shell with regular hexagonal pores; its diameter twice as long as the equal distance between every two concentric shells. Radial spines twenty to forty, each with twenty to twenty-four verticils.

_Dimensions._--Diameter of the innermost shell 0.1; distance between the concentric shells 0.05.

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

2. _Arachnopila polygonella_, n. sp.

Innermost shell with irregular, polygonal pores; its diameter fully as long as the equal distance between every two concentric shells. Radial spines sixty to eighty, each with twelve to sixteen verticils.

_Dimensions._--Diameter of the innermost shell 0.04; distance between the concentric shells 0.04.

_Habitat._--Central Pacific, Station 266, surface.

{267}Genus 109. _Arachnopegma_,[147] Haeckel, 1881, Prodromus, p. 454.

_Definition._--#Astrosphærida# with five to ten or more cortical, concentric, polyhedral, or spherical lattice-shells, composed of a very thin, cobweb-like network; innermost shell with hexagonal or polygonal meshes; other shells with simple triangular meshes, connected to one another by diagonal threads between them.

The genus _Arachnopegma_ differs from its ancestral form _Arachnopila_, in the possession of peculiar diagonal threads, which connect the verticils or nodal-points of every two neighbouring radial spines in two different neighbouring concentric shells. In this case, therefore, not only do triangular meshes lie in the spherical faces of the concentric spheres, but also between them, in numerous oblique diagonal planes; a very rare and remarkable structure, and forming a transition to spongy shells.

1. _Arachnopegma verticillatum_, n. sp.

Innermost shell with regular, hexagonal meshes; its diameter is the same as the equal distance between each of the two shells. Threads of the network smooth. Radial spines twenty to forty, each with fifteen to twenty verticils.

_Dimensions._--Diameter of the innermost shell 0.04, distance between the concentric shells 0.03 to 0.04.

_Habitat._--Central Pacific, Station 266, surface.

2. _Arachnopegma longispinum_, n. sp.

Innermost shell with regular, hexagonal meshes; its diameter half as large as the equal distance between every two shells. Threads of the network dentated or with small knots. Radial spines fifty to sixty, each with twenty to twenty-five verticils.

_Dimensions._--Diameter of the innermost shell 0.02; distance between the concentric shells 0.04 to 0.05.

_Habitat._--Central Pacific, Station 272, surface.

3. _Arachnopegma increscens_, n. sp.

Innermost shell with regular, hexagonal meshes; its diameter quite as large as the distance between it and the second shell; only half as large as the distance between the fourth and fifth shells. Forty to fifty radial spines, each with fifteen to twenty verticils.

_Dimensions._--Diameter of the innermost shell (A) 0.025; distance between the following shells--A, B = 0.025, B, C = 0.03, C, D = 0.04, D, E = 0.048, E, F = 0.056, F, G = 0.064, &c.

_Habitat._--Central Pacific, Station 274, surface.

{268}Genus 110. _Arachnosphæra_,[148] Haeckel, 1862, Monogr. d. Radiol., p. 355.

_Definition._--#Astrosphærida# with five to ten or more cortical, concentric, polyhedral, or spherical lattice-shells, composed of a very thin cobweb-like network; innermost shell with hexagonal (regular) or polygonal (irregular) meshes; other shells with larger, irregular, polygonal meshes.

The genus _Arachnosphæra_ (accurately described by me in 1862, _loc. cit._) differs from the two preceding genera in the irregular form of the large meshes in all shells (except often the innermost). This is caused by the ramification of the thin threads, which on each shell connect the neighbouring spines. In _Arachnopila_ and _Arachnopegma_ the threads pass directly and undivided from each spine to the neighbouring spine (three pairs from the three edges), and therefore all meshes are triangular. In _Arachnosphæra_ they become polygonal by irregular ramification of the threads. There are here no diagonal threads.

Subgenus 1. _Arachnosphærella_, Haeckel.

_Definition._--Pores of the innermost shell regular, hexagonal.

1. _Arachnosphæra oligacantha_, Haeckel.