Chapter XI: Literature and History (37)

The genus _Tessaraspis_ introduces the series of Lychnaspida, which comprise all those Dorataspida in which the shell is composed of twenty plates, each of which is perforated by four primary aspinal pores. In _Tessaraspis_ and _Lychnaspis_ each plate exhibits only these four primary pores, whilst in _Icosaspis_ and _Hylaspis_ they become surrounded by a circle of secondary or coronal pores. If in _Stauraspis_, the common ancestral form of the Tessaraspida, the four crossed apophyses of each single radial spine became recurved and united together, we should have the typical plate of _Tessaraspis_, in which the piercing radial spine is surrounded by four crossed pores of equal size. The number of sutural pores, between the neighbouring plates, is variable; usually each plate is surrounded by a circle of eight to twelve sutural pores. The sutures between the meeting condyles of the apophyses usually remain open; but in some species they become obliterated (subgenus _Tessaraspidium_).

Subgenus 1. _Tessarasparium_, Haeckel.

_Definition._--Condyles of the neighbouring plates connected by permanent open sutures; therefore the whole shell is composed of twenty separated pieces of acanthin.

{836}1. _Tessaraspis arachnoides_, n. sp. (Pl. 136, fig. 1).

Parmal pores pentagonal, ten to twenty times as broad as the thin thread-like bars, on an average of about the same size as the irregular sutural meshes; the majority of the latter are either triangular or hexagonal. Radial spines very thin and long, cylindrical, their outer part two to four times as long as the inner. As the insertion of the spines is on the highest point of the plates, the shell becomes polyhedral (dodecahedral?).

_Dimensions._--Diameter of the shell 0.15 to 0.17, of the parmal meshes 0.02 to 0.025, sutural meshes 0.01 to 0.03, bars 0.002.

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

2. _Tessaraspis pentagonalis_, n. sp.

Parmal meshes pentagonal, three to four times as broad as the thick bars, and on an average smaller than the irregular polygonal sutural meshes. Radial spines stout, quadrangular; their outer pyramidal part shorter than the inner prismatic part.

_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.01 to 0.012, bars 0.003.

_Habitat._--Central Pacific, Station 269, surface.

3. _Tessaraspis tetragonalis_, n. sp.

Parmal meshes tetragonal, or nearly square, six to eight times as broad as the thin bars, and on an average larger than the irregular polygonal sutural meshes. Radial spines thin, quadrangular, prismatic, their outer part longer than their inner.

_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.012 to 0.016, bars 0.002.

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

4. _Tessaraspis hexagonalis_, n. sp.

Parmal meshes hexagonal, ten to twelve times as broad as the thin bars, and on an average larger than the polygonal sutural meshes (the two proximal sides of each hexagonal parmal mesh two to three times as long as the four distal sides). Radial spines cylindrical, thin; their outer part longer than the inner.

_Dimensions._--Diameter of the shell 0.15, of the parmal pores 0.01 to 0.015, bars 0.001.

_Habitat._--North Pacific, Station 254, surface.

5. _Tessaraspis trigonalis_, n. sp.

Parmal meshes triangular, three to four times as broad as the thick bars, and on an average smaller than the irregular sutural meshes (in each plate all four parmal meshes of the same size, formed like an isosceles triangle, the distal base of which is somewhat curved, and convex towards {837}the periphery, whilst the two proximal sides are straight). Radial spines thick, rounded; their outer conical part shorter than the inner cylindrical part.

_Dimensions._--Diameter of the shell 0.1, of the parmal pores 0.01, of the sutural pores 0.01 to 0.02.

_Habitat._--Tropical Atlantic (near Ascension), Station 345, depth 2010 fathoms.

6. _Tessaraspis circularis_, n. sp.

Parmal meshes circular, all eighty of equal size, quite regular, five to six times as broad as the thick bars, on an average larger than the roundish irregular sutural meshes. Radial spines quadrangular, prismatic, the outer part longer than the inner.

_Dimensions._--Diameter of the shell 0.18, parmal pores 0.015 to 0.018, bars 0.003.

_Habitat._--South-east Pacific, Station 300, surface.

7. _Tessaraspis micropora_, n. sp.

Parmal meshes circular, very small, all eighty of the same size, regular, scarcely as broad as the separating thick bars, and much smaller than the large irregular sutural meshes. Radial spines rounded, their outer conical part about as long as the inner cylindrical part.

_Dimensions._--Diameter of the shell 0.08, of the parmal pores 0.003, of the sutural pores 0.005 to 0.015, bars 0.004.

_Habitat._--Western Tropical Pacific, Station 225, surface.

8. _Tessaraspis diodon_, Haeckel.

_Dorataspis diodon_, Haeckel, 1862, Monogr. d. Radiol., p. 417, Taf.
xxii. figs. 1-5.

Parmal meshes roundish, for the most part nearly circular, three to four times as broad as the bars, and on an average smaller than the roundish sutural meshes. Radial spines in the inner part cylindrical; the outer part very short (only one-third or one-fourth of the radius), divided completely into two parallel conical pointed teeth by a deep incision.

_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.01 to 0.012, of the sutural pores 0.01 to 0.03, bars 0.004.

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

9. _Tessaraspis quadriforis_, n. sp.

Parmal meshes irregular, roundish, of nearly equal size, four to six times as broad as the bars, and on an average of the same size as the roundish sutural meshes. Radial spines quadrangular, prismatic in the inner part, which is somewhat longer than the conical outer part.

_Dimensions._--Diameter of the shell 0.16, of the pores 0.012 to 0.018, bars 0.003.

_Habitat._--North Atlantic, Canary and Cape Verde Islands, Station 353, surface.

{838}10. _Tessaraspis irregularis_, n. sp.

Parmal meshes irregular, roundish, of unequal size, three to six times as broad as the bars, and on an average larger than the irregular sutural meshes. Radial spines cylindrical, the outer part longer than the inner part.

_Dimensions._--Diameter of the shell 0.13, parmal pores 0.006 to 0.012, sutural pores 0.005 to 0.01; bars 0.002.

_Habitat._--Central Pacific, Station 270, surface.

Subgenus 2. _Tessaraspidium_, Haeckel.

_Definition._--Condyles of the neighbouring plates grown together and sutures obliterated; therefore the whole shell forms a single piece of acanthin.

11. _Tessaraspis quadrata_, n. sp.

_Tessaraspidium quadratum_, Haeckel, 1882, Manuscript.

Parmal meshes square, four times as broad as the thin bars, on an average of the same size as the polygonal sutural meshes. Radial spines stout, tetrapterous, prismatic, in the outer part longer than in the inner. Sutures of the shell completely obliterated, therefore the whole shell forms one piece.

_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.012, sutural pores 0.01 to 0.015.

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

12. _Tessaraspis rotunda_, n. sp.

Parmal meshes circular, of equal size, twice as broad as the thick bars, on an average smaller than the roundish sutural meshes. Radial spines cylindrical in the inner part, which is somewhat longer than the outer conical part. Sutures of the shell completely obliterated, therefore the whole shell forms one piece.

_Dimensions._--Diameter of the shell 0.12, parmal pores 0.008, sutural pores 0.005 to 0.015.

_Habitat._--North Atlantic, Station 354, surface.

13. _Tessaraspis concreta_, n. sp. (Pl. 136 fig. 5).

Parmal meshes irregular, polygonal or roundish, six to eight times as broad as the narrow and high bars, much larger than the irregular sutural meshes. Radial spines leaf-shaped, compressed, two-edged, pointed at both ends; inner and outer part nearly of equal size. Shell very thick walled; meshes therefore funnel-shaped; sutures completely obliterated, therefore the whole shell forms a single piece.

_Dimensions._--Diameter of the shell 0.09, parmal pores 0.02, sutural pores 0.01.

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

{839}Genus 363. _Lychnaspis_,[403] Haeckel, 1862, Prodromus, p. 468.

_Definition._--#Dorataspida# with twenty plates, which are perforated by eighty aspinal pores (four crossed pores in each plate). Surface covered with numerous by-spines.

The genus _Lychnaspis_, the largest and most common of all Dorataspida, exhibits the same structure of the shell as its ancestral form _Tessaraspis_, and differs from it only in the development of by-spines on the sutural condyles. Many species of this genus are very widely distributed, and appear in large numbers, and some of them are amongst the most graceful and elegant of the Radiolaria.

Subgenus 1. _Lychnasparium_, Haeckel.

_Definition._--Condyles of the neighbouring plates connected by permanent open sutures; therefore the whole shell is composed of twenty separate pieces of acanthin.

1. _Lychnaspis giltschii_, n. sp. (Pl. 135, fig. 3).

Parmal meshes pentagonal, about ten or twelve times as broad as the thin bars, on an average of the same size as the irregular polygonal sutural meshes. By-spines (two hundred to three hundred) very delicate, half as long as the radius, barbed, and zigzag. Radial main-spines very thin and long, straight, cylindrical; their outer part longer than the inner part.

_Dimensions._--Diameter of the shell 0.2, of the parmal pores 0.02, sutural pores 0.01 to 0.03, bars 0.002.

_Habitat._--Tropical Atlantic, Stations 338 to 348, surface.

2. _Lychnaspis capillaris_, n. sp.

Parmal meshes pentagonal, twenty to thirty times as broad as the very thin thread-like bars, on an average of the same size as the irregular polygonal sutural meshes. By-spines (two hundred to two hundred and fifty) very delicate, zigzag, with very small denticles, one-third as long as the radius. Radial main-spines very thin and long, cylindrical, more or less undulated.

_Dimensions._--Diameter of the shell 0.25, parmal pores 0.025, sutural pores 0.02 to 0.04, bars 0.001.

_Habitat._--North Pacific, Station 250, surface.

3. _Lychnaspis maxima_, n. sp.

Parmal meshes pentagonal, six to eight times as broad as the thick bars, for the most part larger than the irregular sutural meshes. By-spines (four hundred to five hundred) nearly as {840}long as the radius, zigzag, with short denticles. Radial spines very long and stout, quadrangularly-prismatic, with four smooth edges.

_Dimensions._--Diameter of the shell 0.3, parmal pores 0.03, sutural pores 0.01 to 0.025, bars 0.004.

_Habitat._--Central Pacific, Stations 271 to 274, surface.

4. _Lychnaspis serrata_, n. sp.

Parmal meshes pentagonal, three to four times as broad as the thick bars, smaller than the irregular sutural meshes. By-spines (two hundred to three hundred) scarcely one-third as long as the radius, zigzag, with strong denticles. Radial spines very long, stout, quadrangularly-prismatic, with four serrated edges.

_Dimensions._--Diameter of the shell 0.22, parmal pores 0.015, sutural pores 0.012 to 0.03, bars 0.004.

_Habitat._--South Atlantic, Station 330, surface.

5. _Lychnaspis wagenschieberi_, n. sp.

Parmal meshes tetragonal, nearly rhombic, three to four times as broad as the thick bars, smaller than the large irregular sutural meshes. By-spines (about two hundred) large, as long as the radius, with long recurved denticles, very zigzag. Radial main-spines very long, four-sided prismatic. This species differs by the form and size of the spines, and by the square form of the parmal pores from the similar _Lychnaspis polyancistra_, of which the late excellent engraver Wagenschieber, of Berlin, has given such a beautiful figure in my monograph (Taf. xxi. fig. 8).

_Dimensions._--Diameter of the shell 0.16, parmal pores 0.014, sutural pores 0.015 to 0.02, bars 0.004.

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

6. _Lychnaspis polyancistra_, Haeckel.

_Dorataspis polyancistra_, Haeckel, 1862, Monogr. d. Radiol., p. 418,
Taf. xxi. figs. 7-9.

Parmal meshes roundish, tetragonal, or nearly square, two to three times as broad as the thick bars, smaller than the irregular sutural meshes. By-spines (about two hundred) thin, half as long as the radius, zigzag, with blunt denticles. Radial main-spines stout, in the inner half cylindrical, in the outer half (of the same length) conical, pointed.

_Dimensions._--Diameter of the shell 0.12, parmal pores 0.012, sutural pores 0.01 to 0.04, bars 0.004.

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

{841}7. _Lychnaspis rottenburgii_, n. sp. (Pl. 135, fig. 4).

Parmal meshes roundish, about twice as broad as the thick bars, and for the most part smaller than the irregular sutural meshes. By-spines (about two hundred to two hundred and fifty) thin, zigzag, half as long as the radius. Radial main-spines very strong, cylindrical in the inner half, in the outer half much thicker and conical, pointed. I call this species in honour of my learned friend, the great patron of zoological studies, Mr. Paul Rottenburg, of Glasgow.

_Dimensions._--Diameter of the shell 0.15, parmal pores 0.012, sutural pores 0.01 to 0.03, bars 0.006.

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

8. _Lychnaspis undulata_, n. sp. (Pl. 135, fig. 2).

Parmal meshes circular, twice as broad as the thick bars, on an average of the same size as the irregular sutural meshes. By-spines (one hundred and fifty to two hundred) very thin, barbed and zigzag, as long as the radius. Radial main-spines cylindrical; their outer pointed part longer than the inner part.

_Dimensions._--Diameter of the shell 0.1, parmal pores 0.01, sutural pores 0.01, bars 0.005.

_Habitat._--Tropical Atlantic, Station 343, surface.

9. _Lychnaspis longissima_, n. sp. (Pl. 134, fig. 6).

Parmal meshes circular, very small, of the same breadth as the thick bars, much smaller than the irregular sutural meshes. By-spines (one hundred to one hundred and ten) very long and thin, zigzag, twice as long as the diameter of the shell. Radial main-spines very long and strong, cylindrical (at the base quadrangular, pyramidal), four to six times as long as the diameter of the shell, and one fourth as thick as its radius.

_Dimensions._--Diameter of the shell 0.08, parmal pores 0.002, sutural pores 0.01 to 0.015, bars 0.003; length of the radial spines 0.3 to 0.5.

_Habitat._--Tropical Pacific (Philippines), Stations 200 to 215, surface.

10. _Lychnaspis minima_, n. sp. (Pl. 134, figs. 2, 7, 8).

Parmal meshes circular, very small, only half as broad as the thick bars, much smaller than the irregular sutural meshes. By-spines (one hundred to one hundred and ten) half as long as the radius, zigzag. Radial main-spines thick, in the inner part cylindrical, in the outer shorter part conical, of very variable size.

_Dimensions._--Diameter of the shell 0.05, parmal pores 0.002, sutural pores 0.006 to 0.012, bars 0.004.

_Habitat._--Antarctic Ocean, Station 154, surface.

{842}Subgenus 2. _Lychnaspidium_, Haeckel.

_Definition._--Condyles of the neighbouring plates grown together and sutures obliterated, therefore the whole shell forms a single piece of acanthin.

11. _Lychnaspis echinoides_, Haeckel.

_Haliomma echinoides_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
Berlin, p.36, Taf. v. figs. 3, 4.

_Haliommatidium echinoides_, J. Müller, 1858, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 22.

_Haliommatidium echinoides_, Haeckel, 1862, Monogr. d. Radiol., p. 422.

Parmal meshes pentagonal or somewhat roundish, four times as broad as the bars, and of about the same size as the polygonal meshes. By-spines (about two hundred) short, zigzag. Radial spines thin; their outer conical part shorter than the inner cylindrical part. Sutures perfectly obliterated, but recognisable by the characteristic pair of divergent by-spines. (Some recent observations on this species, made during 1880 in Portofino, have convinced me that the interpretation of it given in my Monograph, 1862, _loc. cit._, was quite correct.)

_Haliomma ligurinum_, J. Müller (= _Haliommatidium ligurinum_, Haeckel, L. N. 16, p. 423) seems to be closely allied to the preceding.

_Dimensions._--Diameter of the shell 0.12 to 0.14, parmal pores 0.015, sutural pores 0.01 to 0.02, bars 0.004.

_Habitat._--Mediterranean, Nice, Saint Tropez (J. Müller); Portofino near Genoa (Haeckel).

12. _Lychnaspis haliommidium_, n. sp.

_Lychnaspidium haliommidium_, Haeckel, 1882, Manuscript.

Parmal meshes circular, twice as broad as the bars, smaller than the irregular sutural meshes. By-spines (about two hundred) barbed and zigzag, as long as the radius. Radial main-spines four-sided; their outer pyramidal part shorter than the inner prismatic part. Sutures perfectly obliterated.

_Dimensions._--Diameter of the shell 0.1, parmal pores 0.01, sutural meshes 0.015 to 0.02.

_Habitat._--South Atlantic, Station 335, depth 1425 fathoms.

13. _Lychnaspis rabbeana_, n. sp.

Parmal meshes circular, very small, of the same breadth as the bars, and much smaller than the irregular sutural meshes. By-spines (about one hundred) very long and thin, zigzag, about as long as the diameter of the shell. Radial main-spines cylindrical, thick, twice to three times as long as the diameter of the shell. Sutures perfectly obliterated, with thickened condyles. Named in honour of Captain Henrik Rabbe (of Bremen), to whom I am indebted for many new Indian and Atlantic Radiolaria.

_Dimensions._--Diameter of the shell 0.086, parmal pores 0.002, sutural pores 0.012, bars 0.002.

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

{843}14. _Lychnaspis cataplasta_, n. sp.

Parmal pores very small, circular, half as broad as the bars, and much smaller than the irregular sutural pores. By-spines zigzag, as long as the diameter of the shell. Radial main-spines very thin and long, needle-shaped, cylindrical, five to six times as long as the diameter of the shell. Sutures perfectly obliterated. (This stunted species is one of the smallest of the Dorataspida.)

_Dimensions._--Diameter of the shell 0.05, parmal pores 0.0015, sutural pores 0.01, bars 0.002.

_Habitat._--Antarctic Ocean (off Kerguelen Island), Station 149, surface.

Genus 364. _Icosaspis_,[404] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Dorataspida# with twenty plates, which are perforated by one hundred and sixty to three hundred or more parmal pores (in each plate four crossed aspinal pores, and around them four to twelve or more coronal pores). Surface without by-spines.

The genus _Icosaspis_ and the closely allied _Hylaspis_ differ from all other Tessaraspida in the increased number of the parmal pores. Whilst this number in all other genera is eighty (only four crossed pores in each plate), here it amounts to one hundred and sixty to three hundred or more (sometimes more than a thousand); in each shield four primary, crossed "aspinal pores" being surrounded by a circle of four to twelve or more "coronal pores." The number of sutural pores in these two genera is also increased.

Subgenus 1. _Icosasparium_, Haeckel.

_Definition._--Condyles of the neighboring plates connected by permanent open sutures; therefore the whole shell composed of twenty separated pieces of acanthin.

1. _Icosaspis tabulata_, n. sp. (Pl. 136, fig. 2).

Parmal meshes all of nearly equal size and form, square, four times as broad as the bars, little larger than the triangular or polygonal sutural meshes. In each plate fifty to seventy (regularly sixty-four) quadrangular pores, viz., four primary square aspinal meshes, forming together a regular square surrounded by two to three coronas of rectangular (not quite regular) coronal meshes (six to eight in each transverse row). Radial spines tetrapterous, prismatic, with four thin and broad wings, from which arise the crossed bars between the four primary pores. Outer part of the spines longer than the inner. Commonly the condyles of the plates are only contiguous; sometimes they grow together, and this form approaches _Icosaspis tetragonopa_.

_Dimensions._--Diameter of the shell 0.25 to 0.3, of the pores 0.02, bars 0.005.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.

{844}2. _Icosaspis elegans_, n. sp. (Pl. 136, fig. 4; Pl. 134, fig. 9).

_Tessaraspis elegans_, Haeckel, 1882, Manuscript et Atlas.

Parmal meshes of very different size and form; in the centre of each plate a cross of four primary, pear-shaped "aspinal pores" (the largest of all); between them four secondary, little smaller, crossed, egg-shaped "angular pores"; around this rosette of eight larger meshes an inner complete circle of sixteen to twenty polygonal coronal pores, and an outer incomplete circle of thirty to forty very small marginal pores. The latter are smaller than the irregular sutural meshes, which are constricted in the middle, about forty to sixty around each plate. Radial spines thin, cylindrical, or a little compressed; their outer part longer than the inner. In this elegant and very common species the condyles usually remain separated by sutures; but sometimes the latter become obliterated, and the whole shell then forms a single piece, _Icosaspidium elegans_.

_Dimensions._--Diameter of the shell 0.2 to 0.3, commonly 0.25; larger parmal pores 0.02, smaller 0.001 to 0.003; sutural pores 0.005 to 0.015; bars 0.003.

_Habitat._--Tropical and Subtropical Atlantic, Canary Islands to Ascension Island, Stations 340 to 354, surface.

3. _Icosaspis cruciata_, n. sp. (Pl. 134, fig. 10).

Parmal meshes very different; in the centre of each plate a cross of four primary, nearly oblong, rectangular "aspinal pores"; between these four secondary, triangular, egg-shaped "angular pores" (the largest of all), and around this rosette a single circle of twelve to twenty-four small "coronal pores." The latter are of about the same size as the irregular sutural meshes, of which there are twenty to thirty around each plate. Radial spines thin, cylindrical, or a little compressed; their outer part longer than the inner.

_Dimensions._--Diameter of the shell 0.2 to 0.3, commonly 0.25; larger parmal pores 0.025, smaller 0.005 to 0.01; bars 0.005.

_Habitat._--Tropical and Subtropical Pacific, Sandwich to Marquesas Islands, Stations 256 to 274, surface.

4. _Icosaspis ornata_, n. sp.

Parmal meshes very different; in the centre of each plate a cross of four primary octagonal aspinal pores (the largest of all); between them four secondary, rhombic angular pores, and around this rosette a circle of twelve to sixteen smaller, polyhedral coronal pores, which are however larger than the irregular sutural pores (surrounding each plate to the number of twenty to thirty). Radial spines thin, quadrangular, prismatic; the outer part longer than the inner.

_Dimensions._--Diameter of the shell 0.25; larger parmal pores 0.03, smaller 0.01; sutural pores 0.004 to 0.008; bars 0.006.

_Habitat._--South Pacific, Station 295, depth 1500 fathoms.

{845}5. _Icosaspis spectabilis_, n. sp.

Parmal meshes very different; in the centre of each plate four very large, pentagonal aspinal pores, and around these two to three circles of smaller polygonal coronal pores, which are very numerous, and not larger than the small sutural pores. Radial spines quadrangular, prismatic, stout, very long; the outer part two to three times as long as the inner.

_Dimensions._--Diameter of the shell 0.4, of the larger aspinal meshes 0.03, of the outer meshes 0.002 to 0.02, bars 0.005.

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

6. _Icosaspis multiforis_, n. sp.

Parmal meshes very numerous, more than one hundred in each plate; in the centre four larger pear-shaped pores, and around these four to five circles of smaller pores, gradually smaller towards the margin of the plate; the sutural meshes also very small and numerous (more than fifty around each plate), so that the number of all the pores together amounts to two thousand or even more. Radial spines thin, cylindrical, very long.

_Dimensions._--Diameter of the shell 0.32; larger aspinal pores 0.02, smaller 0.002 to 0.01; bars 0.003.

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

Subgenus 2. _Icosaspidium_, Haeckel.

_Definition._--Condyles of the neighbouring plates grown together, and sutures obliterated; therefore the whole shell forms a single piece of acanthin.

7. _Icosaspis tetragonopa_, Haeckel.

_Haliommatidium tetragonopum_, Haeckel, 1862, Monogr. d. Radiol., p.421,
Taf. xxii. fig. 13.

Parmal meshes all of nearly equal size and form, square, three times as broad as the bars, little larger than the sutural meshes. In each plate commonly sixteen equal square meshes, viz., four primary aspinal and twelve secondary, surrounding the former as a square corona. Radial spines tetrapterous, stout; the outer pyramidal half somewhat longer than the inner. This species differs from the similar _Icosaspis tabulata_ (Pl. 136, fig. 2) in the concrescence of the sutures, the smaller number of pores, and the form of the stouter spines. The figure in my Monograph, drawn from a broken fragment, is not quite correct.

_Dimensions._--Diameter of the shell 0.18, pores 0.009, bars 0.003.

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

8. _Icosaspis icosahedra_, n. sp.

Parmal meshes of different size and form; in the centre of each plate a cross of four pentagonal, primary aspinal pores, surrounded by a complete corona of twelve to sixteen polygonal coronal {846}pores and an incomplete corona of thirty to forty very small marginal pores; the latter are not to be distinguished from the pores of the obliterated sutures. Radial spines quadrangular, the outer pyramidal part shorter than the inner prismatic part. Condyles grown together. As the plates are quite even, the shell becomes icosahedral.

_Dimensions._--Diameter of the shell 0.16, pores 0.002 to 0.02, bars 0.005.

_Habitat._--North Pacific, Station 241, surface.

9. _Icosaspis icosastaura_, n. sp. (Pl. 136, fig. 3).

_Tessaraspis icosastaura_, Haeckel, 1882, Manuscript et Atlas.

Parmal plates of different size and form; in the centre of each plate a cross of four larger primary, pyriform aspinal pores; between these four smaller roundish angular pores, and around this rosette a circle of ten to twenty (commonly sixteen) coronal pores, little larger than the very small sutural pores. Radial spines very thin and long, cylindrical or bristle-shaped. Condyles grown together; no suture visible.

_Dimensions._--Diameter of the shell 0.14; larger pores of the cross 0.01, smaller pores 0.002 to 0.008; bars 0.002 to 0.004.

_Habitat._--Central Pacific, Station 268, surface.

Genus 365. _Hylaspis_,[405] n. gen.

_Definition._--#Dorataspida# with twenty plates, which are perforated by one hundred and sixty to three hundred or more parmal pores (in each plate four crossed aspinal pores, and around them four to twelve or more coronal pores). Surface covered with numerous by-spines.

The genus _Hylaspis_ exhibits the same structure of the shell as the nearly allied ancestral genus _Icosaspis_, and differs from it only in the development of by-spines. Some species of these two genera exhibit the highest degree of complication in the structure of the shell seen among the Dorataspida.

1. _Hylaspis serrulata_, n. sp. (Pl. 135, fig. 1).

Parmal meshes four hundred to five hundred; in the centre of each plate a cross of four very large pentagonal or roundish aspinal pores, and around this a circle of sixteen to twenty much smaller irregular, polygonal, coronal pores; the latter of about the same size as the sutural pores. On each condyle one thin zigzag-shaped by-spine, nearly as long as the radius. Twenty radial spines very long, quadrangular, prismatic; on the inside thinner and smooth, on the outside thickened, and armed with four rows of recurved teeth, serrated.

_Dimensions._--Diameter of the shell 0.18, aspinal spines 0.02, other pores 0.002 to 0.01, bars 0.003.

_Habitat._--South Atlantic, Station 326, surface.

{847}2. _Hylaspis coronata_, n. sp.

Parmal meshes five hundred to six hundred; in the centre of each plate a cross of four long rectangular aspinal pores, between these four larger egg-shaped angular pores; around this rosette a circle of sixteen to twenty much smaller, irregular, roundish, coronal pores; the latter about of the same size as the sutural pores. On each condyle one bearded by-spine about one-third or one-fourth as long as the radius. Twenty radial spines, very long, smooth, quadrangular, prismatic.

_Dimensions._--Diameter of the shell 0.25, aspinal pores 0.02, other pores 0.005 to 0.01, bars 0.004.

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

3. _Hylaspis barbata_, n. sp.

Parmal meshes twelve hundred to sixteen hundred; in the centre of each plate a cross of four large, somewhat oblong, octahedral aspinal pores, between these four rhombic smaller angular pores; around this rosette an inner circle of twelve to sixteen larger and an outer circle of fifty to sixty very small coronal pores; the latter smaller than the sutural pores. On each condyle one bristle-shaped zigzag by-spine, with recurved thin hooks, half as long as the radius. Twenty radial spines, very long, cylindrical, smooth.

_Dimensions._--Diameter of the shell 0.25 to 0.3, aspinal pores 0.022, other pores 0.002 to 0.015, bars 0.002.

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

Family XLI. #PHRACTOPELTIDA#, Haeckel (Pl. 133, figs. 1-6).

_Phractopeltida_, Haeckel, 1881, Prodromus, p. 468.

_Definition._--ACANTHARIA with double spherical lattice-shell, composed of the branched apophyses of twenty radial spines meeting in its centre, and disposed according to the Müllerian law of Icosacantha. Central capsule spherical, enclosing the inner and surrounded by the outer concentric shell.

The family #Phractopeltida# differs from all other ACANTHARIA in the development of a double spherical shell, composed of two concentric lattice-spheres, which are united by twenty radial spines meeting in the common centre. We could therefore oppose the Phractopeltida as _Diplophracta_ to all other #Acanthophracta# as _Haplophracta_ (with simple shell). The former exhibit a relation to the latter, similar to that exhibited by the Dyosphærida to the simple Monosphærida among the #Sphæroidea#.

In my Monograph (1862, p. 423) I described only one genus appertaining to this family, _Aspidomma_. I founded it upon the singular _Phractopelta_, described by {848}J. Müller as _Haliomma hystrix_. A second species of _Aspidomma_, the _Acanthometra mucronata_ of J. Müller, was probably an _Astrolonche_. At that time I placed _Aspidomma_ among the Haliommatida, led by the erroneous opinion that it might represent a transition-form between _Dorataspis_ and _Haliomma_. But I afterwards gave up this view, as I was convinced that there is no true phylogenetic connection between the acanthinic Dorataspida (_Actipylea_) and the siliceous Haliommatida (_Peripylea_). Therefore in my Prodromus (1881, p. 468) I placed _Aspidomma_ among the Dorataspida and changed its name to _Phractopelta_, to avoid further confusion with the unrelated Ommatida (#Sphæroidea#). It formed there, with three nearly related genera, the "subfamily Phractopeltida," which we now advance to the higher rank of a separate family. (By a typographical mistake the words are printed in the Prodromus _Phractopelma_ and Phractopelmida, &c., instead of _Phractopelta_ and Phractopeltida, &c.). The detection of other new species appertaining to this family, and a closer anatomical investigation of them, has now led to the distinction of five different genera, characterised by other differences than were employed in 1881 in the provisional system of the "Prodromus."

The two concentric spherical lattice-shells of the Phractopeltida, connected by radial beams, correspond perfectly to those of the double-shelled Dyosphærida (_Haliomma_, _Diplosphæra_, &c.), and in both cases we may call the smaller inner the "medullary shell," and the larger outer the "cortical shell." There is no doubt that the double-shelled Phractopeltida must be derived phylogenetically from the simple-shelled Dorataspida (just as we derive the double Dyosphærida from the simple Monosphærida). But it is not yet possible to decide positively which of the two shells is the first formed. Probably the small inner or medullary shell of the Phractopeltida is the first formed, and corresponds to the simple spherical lattice-shell of the Dorataspida; and the larger outer or cortical shell of the former is a later new formation, absent in the latter family. This opinion seems to be confirmed by the genus _Orophaspis_, the only form among the Dorataspida, in which the radial spines outside the shell bear free latticed apophyses. If these twenty apophyses grow further and meet one another, the second or outer shell of _Phractopelta_ may be formed. But some objections may be raised to this opinion from the peculiar structure and the very small size of the inner shell; and there is some possibility that this latter is a secondary later product inside of the primary cortical shell. The probably phylogenetic series which reveals the origin of the Phractopeltida is the following:--_Acanthometron_, _Zygacantha_, _Lithophyllium_, _Phractacantha_, _Doracantha_, _Dorataspis_, _Orophaspis_, _Phractopelta_.

The twenty radial spines exhibit in all Phractopeltida the same characteristic position and relation as in all other Icosacantha, and are constantly arranged according to the Müllerian law in four meridian planes, their distal ends falling into five parallel zones. Their distinction in the majority of the Phractopeltida is not difficult, {849}since the spines of the different zones bear apophyses of different shapes. Sometimes the four equatorial spines are stouter than the sixteen other spines, and often the eight tropical spines are somewhat different in form from the eight polar and from the four equatorial spines. The length of all twenty spines is commonly equal. Their form is usually more or less compressed, two-edged (as in _Zygacantha_), more rarely cylindrical (as in _Acanthometron_), or somewhat quadrangular (but not truly prismatic); therefore the transverse section of the spines is commonly elliptical or lanceolate, rarely circular or rhombic, never square; this seems to indicate their origin from _Zygacantha_. As in all ACANTHARIA, the spines consist of acanthin, not of silex. Their central ends are either perfectly grown together, and form a single star of acanthin, or the triangular faces of their small pyramidal bases are supported one upon another, without true concrescence.

The apophyses of the radial spines, by which the two concentric spherical shells are formed, seem to be constantly four on each spine, two being opposite in each shell. The proximal pair of opposite apophyses, forming the inner or medullary shell, is constantly much smaller than the distal pair composing the outer or cortical shell (Pl. 133, fig. 5). The proximal pair corresponds probably to the two primary apophyses of the Diporaspida (_Phractaspis_, _Dorataspis_, &c.), whilst the distal pair corresponds to the free apophyses of _Orophaspis_ (Pl. 133, fig. 6). Therefore the Phractopeltida may be derived phylogenetically from the Diporaspida (not from the Tessaraspida). In the common ancestral genus of this family, _Phractopelta_, the free part of the radial spines (outside the outer shell) is quite simple, without free apophyses; in all other genera of the family that free part of the spines (either in all twenty spines or only in some of them) bears a third pair of lateral apophyses; these may be either simple or branched or even latticed; but the outer apophyses (of the third rank) remain constantly free, and a third lattice-shell is never formed by union of their edges (Pl. 133, figs. 2-4).

The inner lattice-shell of the Phractopeltida, or their "medullary shell," is constantly very small (commonly 0.03 to 0.05 mm. in diameter, rarely more). Its structure is difficult to make out; in the unbroken shell it is concealed by the dense network of the outer shell; in the broken shell it is commonly destroyed. Usually the pores of the inner shell are very small, circular or subcircular, scarcely as broad as the small separating bars. In the majority of Phractopeltida their number seems to be about forty, being probably the forty primary aspinal pores of the Diporaspida; in some species this number seems to be exceeded, so that perhaps some sutural pores may exist between the aspinal pores; but commonly the twenty plates composing the inner shell (each with two aspinal pores) seems to grow together perfectly by their meeting edges, so that there are no sutural pores between them. Evident sutures were not recognisable in the inner shell of any Phractopeltida.

{850}The outer lattice-shell of the Phractopeltida, or their "cortical shell," is at least twice as broad, commonly about three times as broad, as the enclosed inner shell; it is much more varied in composition than the latter. Like the greater part of the Dorataspida we may distinguish here in the lattice-work two kinds of pores--parmal pores and sutural pores. The parmal pores are produced by the union of the meeting branches of the apophyses of each single spine, and are therefore visible on each isolated spine; whilst the sutural pores are formed by the meeting branches of the apophyses of neighbouring spines. The distinction of the parmal and the sutural pores, easy in most Dorataspida, is difficult in most Phractopeltida, because the sutures between the meeting branches are usually very early obliterated. However, the place of the obliterated suture is often indicated by the thickened condyles of the apophyses on both sides of the suture. Commonly also the form of the sutural pores is much more irregular than that of the parmal pores; the former are more or less constricted in the middle by the intumescence of the sutural condyles, whilst the latter are more roundish, elliptical, kidney-shaped, or square. The number of the pores in the outer shell in the typical normal form of Phractopeltida seems to be the same as in the most species of _Dorataspis_, _Diporaspis_, &c., between ninety and one hundred, viz., forty parmal pores and from fifty to sixty sutural pores. However, in many species this number is increased. Since in all Phractopeltida, each of the twenty plates is composed only of the meeting branches of two opposite apophyses, we find originally in each plate only two primary parmal pores or "aspinal pores." But in some species there occur four, six, or more pores in each plate; in this case two of them only are aspinal pores, all the others being "coronal pores." Moreover, in those species which exhibit on the base of each spine in the outer shell four crossed pores (Pl. 133, fig. 2), there are not four equivalent aspinal pores (as in the Tessaraspida), but the two opposite are primary or aspinal pores and the other two (different from them in size and form) coronal pores. However, the number of coronal pores in the Phractopeltida is never so large as in many Dorataspida, and the same holds good also for the increasing number of the irregular sutural pores. In none of the species observed does the total number of the pores in the outer shell reach two hundred.

The original mode of development of the apophyses composing the outer shell seems to be imitated by the free apophyses of the third order, which are developed from the radial spines outside the outer shell in all Phractopeltida, with the single exception of the simple ancestral genus _Phractopelta_. These apophyses of the third rank are also originally constantly two, opposite to one another (after the type of _Lithophyllium_, _Dorataspis_, &c.). Commonly they do not remain simple, but become branched, and by communication of the neighbouring branches small lattice-plates arise. Originally each of these free lattice-plates has only two parmal pores, but the number of the parmal pores increases afterwards, so that we may distinguish two (primary) {851}aspinal pores, and two, four, or more (secondary) coronal pores. In the majority of species the two opposite apophyses are first crossed at right angles by a transverse beam, and the two parallel transverse beams are again crossed by perpendicular tertiary branches (again parallel to the apophyses). In this case the network of the free lattice-plates becomes more or less rectangular. But in other species the ramification of the apophyses assumes more the form of bifurcation or of irregular branching. As already said, the neighbouring free lattice-plates of this third order never meet, and therefore a complete third shell is never formed.

The different genera of Phractopeltida exhibit very remarkable differences in the development of free apophyses (or lattice-plates of the third order). Whilst in the numerous species of the ancestral genus _Phractopelta_ all twenty spines remain simple, without such apophyses, only in a single observed species (representing the genus _Pantopelta_) were all twenty spines protected by them. In the three other genera only one part of the spines bears free apophyses, but not the other part. The most frequent form is _Dorypelta_ (Pl. 133, fig. 2); here eight spines are simple (four equatorial and four polar spines of the hydrotomical plane), whilst twelve spines bear apophyses (eight tropical and four polar spines of the geotomical plane). In _Octopelta_ the eight tropical spines only bear apophyses, whilst the twelve other (four equatorial and eight polar) are simple. In _Stauropelta_ finally the four equatorial spines only are simple, whilst the sixteen other bear free apophyses (eight tropical and eight polar spines).

_The Central Capsule_ of the Phractopeltida is constantly spherical, and enclosed between the two concentric spherical shells; it is therefore larger than the inner and smaller than the outer shell. Its wall is pierced by the twenty radial beams connecting the two shells. The shape of the central capsule and of the enveloping calymma is the same as in the other #Acanthophracta# and specially in the Dorataspida.

_Synopsis of the Genera of Phractopeltida._

{All twenty spines without
{ apophyses in the free
All twenty spines of the { external part, 366. _Phractopelta_.
same form, {
{All twenty spines with
{ apophyses in the free
{ part, 367. _Pantopelta_.

{Eight tropical spines with
{ apophyses, twelve others
{ (eight polar and four
{ equatorial) simple, 368. _Octopelta_.
{
{Twelve radial spines
Twenty radial spines, { (eight tropical and four
partly without, partly { polar) with apophyses,
with apophyses in the { eight others (four polar
free external part, { and four equatorial)
{ simple, 369. _Dorypelta_.
{
{Sixteen radial spines
{ (eight tropical and
{ eight polar) with
{ apophyses, four
{ equatorial, simple, 370. _Stauropelta_.

{852}Genus 366. _Phractopelta_,[406] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Phractopeltida# with twenty simple radial spines, bearing no free apophyses outside the outer shell.

The genus _Phractopelta_ is the most simple form among the Phractopeltida, and may be regarded as the common ancestral form of this family. All twenty spines are of nearly equal form and size, and bear no free apophyses on their free part, outside the two concentric shells. _Phractopelta_ may be derived from _Orophaspis_ by further development of the free apophyses, which by union of their branches form a second outer shell around the primary shell of that Dorataspid.

Subgenus 1. _Phractopeltaris_, Haeckel.

_Definition._--Outer shell composed of twenty separated plates, the sutures of their meeting condyles not being grown together.

1. _Phractopelta dorataspis_, n. sp. (Pl. 133, fig. 1).

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with two elliptical aspinal pores, which are two to three times as broad as the irregular sutural pores. Radial spines (in the outer free part) compressed, linear, twice as long as the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.05.

_Habitat._--North Pacific (off Japan), Station 239, surface.

2. _Phractopelta dyadopora_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with two kidney-shaped aspinal pores, which are three to four times as broad as the irregular sutural pores. Radial spines conical, about as long as the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.04.

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

3. _Phractopelta diporaspis_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with two quadrangular aspinal pores, which are four to five times {853}as broad as the irregular sutural pores. Radial spines compressed, sword-shaped, about as long as the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.04.

_Habitat._--South Atlantic, Station 332, surface.

4. _Phractopelta tessaraspis_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with four crossed, quadrangular, aspinal pores, the two opposite of which are much larger than the two others. Sutural pores small, roundish. Radial spines compressed, linear, about twice as long as the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.084, of the inner 0.032.

_Habitat._--North Pacific (off Japan), Station 238, surface.

5. _Phractopelta tetradopora_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with four crossed quadrangular (or nearly circular) aspinal pores, all of nearly the same size. Sutural pores polygonal or roundish. Radial spines cylindrical, two to three times as long as the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.045.

_Habitat._--North Pacific, Station 253, surface.

6. _Phractopelta hexadopora_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with six aspinal pores, the two opposite of which are much larger than the four others. Sutural pores small, roundish. Radial spines compressed, two-edged, larger than the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04.

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

7. _Phractopelta octadopora_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with eight aspinal pores, the four crossed being larger than the four others alternating with them. Sutural pores irregular. Radial spines conical, shorter than the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.04.

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

{854}Subgenus 2. _Phractopeltidium_, Haeckel.

_Definition._--Outer shell composed of twenty united plates, the sutures of their meeting condyles being grown together.

8. _Phractopelta aspidomma_, n. sp.

Outer shell composed of twenty united plates, the meeting condyles of which are grown together. On the base of each radial spine (where its outer free part arises from the surface of the outer shell), two large elliptical aspinal pores, two to four times as large as the other roundish pores. Radial spines compressed, sword-shaped, about as long as the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.05.

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

9. _Phractopelta haliomma_, n. sp.

Outer shell composed of twenty united plates, the meeting condyles of which are grown together. On the base of each radial spine two large kidney-shaped aspinal pores, little larger than the other irregular pores. Radial spines compressed, linear, two-edged, much longer than the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.03.

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

10. _Phractopelta tessaromma_, Haeckel.

Outer shell composed of twenty united plates, the meeting condyles of which are grown together. On the base of each radial spine four crossed egg-shaped aspinal pores, two opposite of which are much larger than the two others. Sutural pores irregular. Radial spines cylindrical or little compressed, thin, longer than the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04.

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

11. _Phractopelta hystrix_, Haeckel.

_Haliomma hystrix_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 37, Taf. v. figs. 1, 2.

_Aspidomma hystrix_, Haeckel, 1862, Monogr. d. Radiol., p. 424.

Outer shell composed of twenty united plates, the meeting condyles of which are grown together. On the base of each radial spine four crossed circular aspinal spines of equal size. Sutural pores roundish, of about the same size. Radial spines conical, about as long as the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.07, of the inner 0.024.

_Habitat._--Mediterranean (Nice), J. Müller, surface.

{855}Genus 367. _Pantopelta_,[407] n. gen.

_Definition._--#Phractopeltida# with twenty radial spines, each of which is protected by two free external apophyses.

The genus _Pantopelta_ differs from all other Phractopeltida in the development of free protecting apophyses on all twenty radial spines. Only a single specimen of this rare form was seen, and in this all twenty spines exhibited no marked differences in form and size, but were more or less irregularly developed.

1. _Pantopelta icosaspis_, n. sp. (Pl. 133, fig. 4).

Apophyses of all twenty radial spines with forked anastomosing branches, forming a more or less irregular cup-like fenestrated shield, pierced by a variable number of pores. Distance of the apophyses from the outer shell equal to half its radius. Pores of the outer shell irregular, roundish, four to six times as broad as those of the inner shell. Radial spines compressed, sword-shaped, longer than the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.03.

_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms.

Genus 368. _Octopelta_,[408] n. gen.

_Definition._--#Phractopeltida# with twelve simple spines (four equatorial and eight polar), and with eight tropical spines protected by external free apophyses.

The genus _Octopelta_ differs from the other Phractopeltida in the possession of eight shields or pairs of free apophyses outside the outer lattice-shell; the spines bearing these apophyses are the eight tropical spines. The twelve other spines (eight polar and four equatorial) are quite simple, without apophyses.

1. _Octopelta cultella_, n. sp.

Apophyses of the eight tropical spines simple, compressed, knife-shaped, about as long as their distance from the outer shell. On the base of each spine (in the network of the outer shell) two orthogonal aspinal pores, two to three times as long as the other polygonal pores.

_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.03.

_Habitat._--Tropical Atlantic, Station 338, surface.

{856}2. _Octopelta furcella_, n. sp.

Apophyses of the eight tropical spines forked, each with two parallel simple fork-branches, about as long as their distance from the outer shell. On the base of each spine (in the outer shell) two kidney-shaped aspinal pores, about twice as broad as the other irregular pores.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04.

_Habitat._--South Atlantic (off Tristan d'Acunha), Station 332, surface.

3. _Octopelta scutella_, n. sp. (Pl. 133, fig. 5).

Apophyses of the eight tropical spines crossed by a transverse beam, which is again crossed by two perpendicular branches; by union of these branches each tropical spine forms a square shield with four crossed pores and twelve to sixteen marginal spikes. On the base of each spine (in the surface of the outer shell) four crossed aspinal pores which correspond to those of the free shields; these are somewhat larger than the other pores.

_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.06.

_Habitat._--Tropical Atlantic, Station 348, surface.

Genus 369. _Dorypelta_,[409] Haeckel, Prodromus, p. 369.

_Definition._--#Phractopeltida# with eight simple spines (four equatorial and four hydrotomical polar spines) and with twelve spines protected by external free apophyses (eight tropical and four geotomical polar spines).

The genus _Dorypelta_, the most common of all Phractopeltida which are protected by free apophyses, exhibits a very peculiar differentiation of its twenty radial spines. There are constantly eight simple spines and twelve spines with apophyses. The eight simple spines are the four equatorial spines and four polar spines placed in the hydrotomical median plane. The four other polar spines (placed in the geotomical meridian plane) and the eight tropical spines are protected by two opposite apophyses, which are now simple, now branched or shield-shaped. A similar differentiation occurs in no other Acanthophractida.

Subgenus 1. _Dorypeltarium_, Haeckel.

_Definition._--Free apophyses of the radial spines simple, not branched.

{857}1. _Dorypelta stauroptera_, n. sp.

Apophyses of the long compressed radial spines simple, conical, about as long as their distance from the shell. At the base of each spine (in the outer shell) two elliptical aspinal pores, two to three times as large as the other pores.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.044.

_Habitat._--North Pacific, Station 238, surface.

2. _Dorypelta gladiata_, n. sp.

Apophyses of the long cylindrical radial spines simple, triangular, about half as long as their distance from the shell. At the base of each spine (in the outer shell) four crossed aspinal pores, the two opposite of which are much larger than the other two pores.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.04.

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

Subgenus 2. _Dorypeltidium_, Haeckel.

_Definition._--Free apophyses of the radial spines branched, with free (not anastomosing) branches.

3. _Dorypelta furcata_, n. sp.

Apophyses of the long compressed spines simply forked, each with two simple parallel fork-branches. At the base of each spine two elliptical aspinal pores, much larger than the other roundish pores.

_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.04.

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

4. _Dorypelta tetrodon_, n. sp.

Apophyses of the long compressed spines crossed by a transverse beam, which bears four simple parallel fork-branches or spikes (perpendicular to the beam), two larger medial and two smaller lateral. At the base of each spine four crossed aspinal pores of nearly equal size, little different from the other pores.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.035.

_Habitat._--South Pacific, Station 284, surface.

5. _Dorypelta ramosa_, n. sp.

Apophyses of the long cylindrical spines crossed by a transverse beam, which bears four to six irregularly branched spikes or fork-branches, the medial of which are larger than the lateral. At {858}the base of each spine four crossed aspinal pores, two opposite of which are much larger than the two other pores.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.04.

_Habitat._--South Pacific, Station 302, surface.

Subgenus 3. _Dorypeltonium_, Haeckel.

_Definition._--Free apophyses of the radial spines branched, and forming perforated shields by union of their anastomosing branches.

6. _Dorypelta lithoptera_, n. sp.

Apophyses of the long compressed radial spines with anastomosing branches; each spine bearing two free separated shields (each with two roundish aspinal pores). At the base of each spine (in the network of the outer shell) two elliptical aspinal pores, larger than the other pores.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.03.

_Habitat._--North Pacific, Station 239, surface.

7. _Dorypelta tessaraspis_, n. sp. (Pl. 133, fig. 2).

Apophyses of the long cylindrical spines with anastomosing branches; each spine bearing a single free shield with four crossed aspinal pores of equal size (on the margin of the shield twelve to sixteen spikes). At the base of each spine (in the outer shell) four crossed aspinal pores, about as large as the other roundish pores.

_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.05.

_Habitat._--Central Pacific, Station 263, surface.

8. _Dorypelta dodecaspis_, n. sp.

Apophyses of the long two-edged spines with anastomosing branches; each spine bearing a single free shield with six to eight parmal pores (four crossed aspinal pores alternating with four outer coronal pores), on the margin of each shield twelve to sixteen spikes. At the base of each spine (in the outer shell) four crossed aspinal pores, about as large as the other irregular pores.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04.

_Habitat._--North Pacific (off Japan), Station 235, surface.

Genus 370. _Stauropelta_,[410] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Phractopeltida# with four simple equatorial spines and sixteen spines protected by external free apophyses (eight tropical and eight polar spines).

{859}The genus _Stauropelta_ is distinguished from the other Phractopeltida by the possession of sixteen pairs of free apophyses (on the eight tropical and the eight polar spines); only the other four equatorial spines remain simple, without apophyses, and form a simple cross in the equatorial plane.

1. _Stauropelta cruciata_, n. sp. (Pl. 133, fig. 3).

Apophyses of the long polar and tropical spines crossed by a transverse beam, which is again crossed by two perpendicular branches parallel to the apophyses; branches with free ends, not united by concrescence. At the base of each spine (in the outer shell) two large elliptical aspinal pores, larger than the other irregular pores. Four equatorial spines simple, without apophyses, of the same size as the other sixteen spines.

_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.05.

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

2. _Stauropelta stauropora_, n. sp.