Chapter XXIX: Section IV: STICHOCYRTIDA, Haeckel, 1862, Monogr. d. Radiol., p. 280, 312 (4)

Shell smooth, nearly spindle-shaped, with four sharp strictures, very similar to the preceding in size and form. It differs in the smooth surface, the absence of longitudinal ribs, and the unequal size of the pores, which form four transverse series in each joint, and are much larger in the broadest (fourth) joint. Proportion of the five joints = 2 : 2 : 3 : 5 : 4.

_Dimensions._--Length of the shell (with five joints) 0.1. Length of the single joints, _a_ 0.012, _b_ 0.012, _c_ 0.02, _d_ 0.03, _e_ 0.025; greatest breadth 0.05.

_Habitat._--Cosmopolitan; Atlantic, Pacific; many stations, in different depths.

15. _Lithocampe heteropora_, Haeckel.

_Lithocampe heteropora_, Haeckel, 1862, Monogr. d. Radiol., p. 317.

_Eucyrtidium heteroporum_, Ehrenberg, 1854, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 242.

Shell smooth, subconical, obtuse, with four distinct strictures. Five joints of different lengths = 2 : 4 : 3 : 3 : 2. The fourth joint is the broadest. Mouth slightly constricted. Pores regular, circular, in the second joint much larger than in the four others, disposed in transverse series; two rows in the first and fifth, three rows in the second, four rows in the third and fourth joints.

_Dimensions._--Length of the shell (with five joints) 0.14. Length of the single joints, _a_ 0.02, _b_ 0.04, _c_ 0.03, _d_ 0.03, _e_ 0.02; greatest breadth 0.07.

_Habitat._--North Atlantic (depth 2000 fathoms, Ehrenberg), Canary Islands, surface, Haeckel.

{1507}16. _Lithocampe meta_, Stöhr.

_Lithocampe meta_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 103, Taf. iv.
fig. 4.

Shell rough, subconical, obtuse, with four slight strictures. Five joints of different lengths = 2 : 4 : 5 : 4 : 2. The fourth joint is the broadest, and three times as broad as the constricted mouth. Pores, small, regular, circular, quincuncially disposed, equal in size; two transverse rows in the first and fifth, five rows in the second and fourth, six rows in the third joint.

_Dimensions._--Length of the shell (with five joints) 0.14. Length of the single joints, _a_ 0.017, _b_ 0.033, _c_ 0.04, _d_ 0.033, _e_ 0.017; greatest breadth 0.083.

_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stöhr), Caltanisetta (Haeckel).

17. _Lithocampe urceolata_, n. sp. (Pl. 77, fig. 2).

Shell rough, wide, urceolate, without external strictures, but with four internal septal rings (not visible in the figure), each of which contains an internal circle of horizontal pores. Five joints of different lengths = 2 : 3 : 6 : 4 : 2. The third joint is the broadest, and three times as broad as the constricted mouth. Pores of very different sizes, irregular, roundish, with prominent polygonal frames. A very remarkable species.

_Dimensions._--Length of the shell (with five joints) 0.17. Length of the single joints, _a_ 0.02, _b_ 0.03, _c_ 0.06, _d_ 0.04, _e_ 0.02; greatest breadth 0.13.

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

18. _Lithocampe clava_, Ehrenberg.

_Lithocampe clava_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 66, Taf. iv. fig. 2.

Shell smooth, club-shaped, or slenderly ovate, with five internal septal rings. Six joints of very different lengths = 5 : 2 : 3 : 4 : 5 : 18. The sixth joint is the broadest, and as long as the five others together. Pores small, circular, in the basal half of the last joint irregular and larger. Constricted mouth as broad as the subspherical, hyaline cephalis.

_Dimensions._--Length of the shell (with six joints) 0.15. Length of the single joints, _a_ 0.02, _b_ 0.011, _c_ 0.013, _d_ 0.016, _e_ 0.02, _f_ 0.07.

_Habitat._--Fossil in Barbados.

19. _Lithocampe hexacola_, n. sp. (Pl. 79, fig. 7).

Shell smooth, nearly spindle-shaped, without external strictures, but with five internal septal rings. Six joints of different lengths = 4 : 8 : 5 : 5 : 5 : 10. The fourth joint is the broadest, and four times as broad as the constricted mouth. Pores subregular hexagonal, or irregular polygonal, with thin bars.

_Dimensions._--Length of the shell (with six joints) 0.18, greatest breadth 0.09. Length of the six joints, _a_ 0.02, _b_ 0.04, _c_, _d_, and _e_ each 0.025, _f_ 0.05.

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

{1508}20. _Lithocampe heptacola_, n. sp. (Pl. 79, fig. 8).

Shell smooth, subcylindrical, constricted at both poles, with six distinct strictures. Seven joints of different lengths, the five abdominal joints nearly equal, each half as long as the hemispherical, vaulted thorax, and twice as long as the subspherical, small cephalis. Mouth constricted, with a short, tubular, hyaline peristome (like an eighth joint without pores), about one-third as broad as each of the four middle joints. Pores subregular hexagonal, or irregular polygonal, with thin bars.

_Dimensions._--Length of the shell (with seven joints) 0.24, greatest breadth 0.09. Length of the cephalis 0.02, thorax 0.06, each of the four following joints 0.03, of the last joint 0.04.

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

21. _Lithocampe octocola_, n. sp. (Pl. 79, fig. 6).

Shell smooth, subcylindrical, thick-walled, constricted at both poles, without distinct, external strictures, but with seven internal septal rings. Eight joints of different lengths; four joints (the second to the fifth) being about twice as long as the four others (the first and the three last). The constricted mouth only one-third as broad as the four middle joints. Pores small and numerous, subregular, circular.

_Dimensions._--Length of the shell (with eight joints) 0.19, breadth 0.09. Length of the second to the fifth joints, each 0.03; length of the four other joints, each about 0.016.

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

22. _Lithocampe polycola_, n. sp.

Shell smooth, subcylindrical, constricted at both poles, with twelve to fifteen distinct strictures. Fourteen to sixteen joints of different lengths. Cephalis flat, cap-shaped, hyaline, without pores. Thorax nearly hemispherical, with three transverse rows of small circular pores. Each following joint (each abdominal joint) only with a single row of small pores. The constricted mouth of the last joint only one-third as broad as the middle part of the shell. (Very similar to _Lithomitra eruca_, Pl. 79, fig. 3.)

_Dimensions._--Length of the shell (with sixteen joints) 0.3, breadth 0.08. Length of the cephalis 0.02, thorax 0.06, each of the following joints 0.015, last joint 0.025.

_Habitat._--Tropical Pacific, Station 224, depth 1850 fathoms.

Genus 651. _Spirocyrtis_,[268] Haeckel, 1881, Prodromus, p. 438.

_Definition._--#Stichocorida# (vel Stichocyrtida eradiata aperta) with spirally-arranged constrictions on the shell. Cephalis with a horn.

The genus _Spirocyrtis_ and the following closely allied genus _Spirocampe_ differ from the other Stichocorida (and also from nearly all #Cyrtoidea#) in a very remarkable {1509}character. The annular constrictions of the multiarticulate shell and the corresponding internal annular septa are here not separated, and do not lie in parallel, transverse planes (as usually happens), but they are all or partly connected in the form of an ascending spiral, so that the joints are not perfectly separated. An irregularity or asymmetry of growth on the different sides of the shell is probably the cause of this strange, spiral structure.

Subgenus 1. _Spirocyrtidium_, Haeckel.

_Definition._--Shell conical, gradually dilating towards the wide open terminal mouth.

1. _Spirocyrtis scalaris_, n. sp. (Pl. 76, fig. 14).

Shell conical, gradually dilating towards the wide open mouth, with ten to twelve spiral convolutions, which correspond to the same number of short and broad chambers or joints, gradually increasing in breadth; all joints form together a spirally winding staircase. The length or height of the single joints or stairs is about equal, and each bears four or five transverse rows of small, square pores. Cephalis flat, cap-shaped, with two or three short divergent horns.

_Dimensions._--Length of the shell (with ten joints or turnings) 0.16, length of each joint (on an average) 0.016; breadth of the third joint 0.04, of the fifth joint 0.07, of the tenth joint 0.1.

_Habitat._--Central Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms.

2. _Spirocyrtis cornutella_, n. sp. (Pl. 76, fig. 13).

Shell conical, gradually dilating towards the wide mouth, similar to the preceding, but differing in the curved axis, and the broader and shorter joints, each of which bears only two or three transverse rows of square pores. The turnings of the staircase are not so sharp, nor so distinct, as in the preceding species. Cephalis with a single short horn.

_Dimensions._--Length of the shell (with eight joints) 0.1; breadth of the fourth joint 0.05, of the eighth joint 0.08.

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

Subgenus 2. _Spirocyrtoma_, Haeckel.

_Definition._--Shell ovate, or nearly spindle-shaped, more or less tapering towards the narrower, somewhat constricted mouth.

3. _Spirocyrtis holospira_, n. sp. (Pl. 76, fig. 16).

Shell subovate, twice as long as broad, without external strictures, but with an internal regularly descending spiral septum, which separates seven to nine broad joints of nearly equal lengths; the {1510}first and second joints together are conical, and about as long as each of the following joints. Cephalis small, hemispherical, with a thick pyramidal horn of the same length. The fifth joint is the broadest, the truncate mouth is slightly constricted (in the specimen figured it is broken off). Pores regular, circular, quincuncial.

_Dimensions._--Length of the shell (with eight joints) 0.2, breadth 0.1; length of each joint, about 0.03.

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

4. _Spirocyrtis hemispira_, n. sp.

Shell slender, nearly spindle-shaped, three times as long as broad, without external strictures, but with ten to eleven internal septa. The five or six upper of these are perfectly separate, complete parallel rings; the five or six lower are spirally connected. The eleven or twelve joints gradually taper in length and breadth, from the broadest middle towards the two constricted ends of the shell. The middle (fifth or sixth) joint is the broadest, and is three to four times as broad as the constricted mouth. Cephalis small, hemispherical, with a conical horn of the same length. Pores regular, circular, hexagonally framed.

_Dimensions._--Length of the shell (with twelve joints) 0.25, breadth 0.09; length of the middle joint 0.03.

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

5. _Spirocyrtis merospira_, n. sp. (Pl. 76, fig. 15).

Shell ovate, with six to eight slight strictures, twice as long as broad. The three or four upper joints are perfectly separated by annular septa, the three or four lower joints connected by an internal spiral septum. The spiral line is often more or less irregular or interrupted (as is also the case in the specimen figured). Mouth rather wide. Pores small, subregular, circular. A rather variable species.

_Dimensions._--Length of the shell (with eight joints) 0.2, breadth 0.1.

_Habitat._--Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.

6. _Spirocyrtis diplospira_, n. sp. (Pl. 76, fig. 17).

Shell slender, ovate, with seven to eight slight strictures. All eight or nine joints are connected by an internal double spiral septum, the first spiral beginning from the ventral side, the second from the dorsal side of the collar stricture. Length and breadth of the single joints rather variable and irregular; the broadest joint is commonly the fifth. Mouth more or less constricted. Pores subregular, circular. This remarkable species differs from all other #Cyrtoidea# by the double spiral septum of the joints.

_Dimensions._--Length of the shell (with eight joints) 0.2, breadth 0.1.

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

{1511}Genus 652. _Spirocampe_,[269] Haeckel, 1881, Prodromus, p. 438.

_Definition._--#Stichocorida# (vel Stichocyrtida eradiata aperta) with spirally arranged constrictions on the shell. Cephalis without horn.

The genus _Spirocampe_ has the same peculiar spiral structure of the shell as the preceding _Spirocyrtis_, and differs from it only in the absence of a cephalic horn. It exhibits, therefore, the same relation to the latter as the similar _Lithocampe_ bears to _Eucyrtidium_.

1. _Spirocampe callispira_, n. sp. (Pl. 76, fig. 11).

Shell ovate, smooth, with six joints, connected in the form of a complete winding staircase. All the windings are nearly at equal distances; each bears one row of large roundish pores, enclosed by two rows of smaller pores. Cephalis hemispherical, of about the same breadth as the constricted, short tubular mouth.

_Dimensions._--Length of the shell (with six joints) 0.15, breadth 0.09; mouth 0.03 diameter.

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

2. _Spirocampe allospira_, n. sp. (Pl. 76, fig. 12).

Shell subcylindrical, or nearly spindle-shaped, smooth, very thick-walled, with eight joints alternately longer and shorter, and connected in the form of an irregular spiral. The distance between the windings is very variable. Pores small, regular, circular. Cephalis hemispherical, of about the same size as the short tubular mouth.

_Dimensions._--Length of the shell (with eight joints) 0.2, breadth 0.08; mouth 0.03 diameter.

_Habitat._--Central Pacific, Station 273, depth 2350 fathoms.

3. _Spirocampe polyspira_, n. sp.

Shell cylindrical, rough, with twelve joints nearly equal in length, connected in the form of a regular, complete spiral. All windings are at the same distance. Pores regular, circular, three rows on each turning. Cephalis flat, cap-shaped, half as broad as the slightly constricted, not tubular mouth.

_Dimensions._--Length of the shell (with twelve joints) 0.24, breadth 0.07; mouth 0.05 diameter.

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

Subfamily 2. STICHOCAPSIDA, Haeckel, 1881, Prodromus, p. 439.

_Definition._--#Lithocampida# with the terminal mouth of the shell fenestrated (vel Stichocyrtida eradiata clausa).

{1512}Genus 653. _Cyrtocapsa_,[270] Haeckel, 1881, Prodromus, p. 439.

_Definition._--#Stichocapsida# (vel Stichocyrtida eradiata clausa) with an apical horn on the cephalis, without basal terminal spine.

The genus _Cyrtocapsa_ and the two following genera represent together the small subfamily of Stichocapsida, or of those #Cyrtoidea# in which the many-jointed shell bears no radial appendages, and the terminal mouth is closed by a lattice-plate. They have been derived from the Stichocorida by development of such a closing plate. _Cyrtocapsa_ bears an apical horn on the cephalis, and may be derived therefore directly from _Eucyrtidium_.

Subgenus 1. _Cyrtocapsella_, Haeckel.

_Definition._--Shell with three annular strictures (or internal septa) and four distinct joints.

1. _Cyrtocapsa tetrapera_, n. sp. (Pl. 78, fig. 5).

Shell rough, pear-shaped, with three deep strictures. The three first joints are of equal lengths, and each half as long as the hemispherical fourth joint. Cephalis subspherical, with an oblique conical horn of the same length. The third joint is the broadest, three times as broad as long. Pores regular, circular.

_Dimensions._--Length of the shell (with four joints) 0.15, breadth 0.09; length of each of the three first joints 0.03, of the last 0.06.

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

2. _Cyrtocapsa compacta_, n. sp. (Pl. 77, fig. 8).

_Eucyrtidium compactum_, Haeckel, 1878, Atlas, loc. cit.

Shell rough, pear-shaped, with three slight strictures. The hemispherical cephalis bears a thick pyramidal spine of the same length, and is half as long as the second and the third joints, one-third as long as the hemispherical fourth joint. The third joint is the broadest, three times as broad as long. Pores subregular, circular. In the centre of the basal pole is one larger pore, the remnant of the constricted mouth of _Eucyrtidium_.

_Dimensions._--Length of the shell (with four joints) 0.16, breadth 0.12. Length of the single joints, _a_ 0.02, _b_ 0.04, _c_ 0.04, _d_ 0.06.

_Habitat._--Western Tropical Pacific, Station 206, depth 2100 fathoms.

{1513}3. _Cyrtocapsa inflata_, n. sp.

Shell spiny, pear-shaped, with three deep strictures. The inflated third joint is twice as long as the second and fourth joints, and three times as long as the hemispherical cephalis, which bears a large conical horn of three times the length. Fourth joint flat, vaulted, inversely cap-shaped. The third joint is the broadest, being twice as broad as long. Pores regular, circular, double-contoured.

_Dimensions._--Length of the shell 0.14, breadth 0.11. Length of the single joints, _a_ 0.02, _b_ 0.03, _c_ 0.06, _d_ 0.03.

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

4. _Cyrtocapsa pyrum_, n. sp. (Pl. 78, fig. 8).

Shell thorny, pear-shaped, without external strictures, but with three internal annular septa. Length of the four joints = 2 : 5 : 6 : 7. The fourth joint is the broadest, being about twice as broad as long, and hemispherical. The small subspherical cephalis bears a stout conical horn of the same length. Pores large, regular, circular.

_Dimensions._--Length of the shell (with four joints) 0.2, breadth 0.12. Length of the single joints, _a_ 0.02, _b_ 0.05, _c_ 0.06, _d_ 0.07.

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

5. _Cyrtocapsa cornuta_, n. sp. (Pl. 78, fig. 9).

Shell rough, very thick-walled, nearly pear-shaped, with three annular strictures; the second of which is very sharp, the first and third slight. Length of the four joints = 3 : 4 : 5 : 6. The third joint is the broadest, being about twice as broad as long; the fourth joint is hemispherical. Cephalis subspherical, with a large, conical, curved horn of twice the length. Pores regular, circular, hexagonally framed.

_Dimensions._--Length of the shell (with four joints) 0.18, breadth 0.12. Length of the single joints, _a_ 0.03, _b_ 0.04, _c_ 0.05, _d_ 0.06.

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

6. _Cyrtocapsa diploconus_, n. sp. (Pl. 78, fig. 6).

Shell rough, doubly conical, with three annular septa. Length of the four joints = 3 : 4 : 4 : 8. The third joint is the broadest, two and a half times as broad as long; the fourth is inversely conical, acute. Cephalis hemispherical, with a pyramidal horn of the same length. Pores irregular, roundish.

_Dimensions._--Length of the shell (with four joints) 0.19, breadth 0.1. Length of the single joints, _a_ 0.03, _b_ 0.04, _c_ 0.04, _d_ 0.08.

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

{1514}7. _Cyrtocapsa fusulus_, n. sp. (Pl. 78, fig. 7).

Shell smooth, spindle-shaped, with three distinct strictures. Length of the four joints = 1 : 1 : 4 : 3. The third joint is the broadest, somewhat longer than broad. The fourth joint is inversely conical. Cephalis hemispherical, with a coronal of large, ovate pores, and a pyramidal, sulcate, oblique horn of twice the length. Pores regular, circular.

_Dimensions._--Length of the shell (with four joints) 0.18, breadth 0.07. Length of the single joints, _a_ 0.02, _b_ 0.02, _c_ 0.08, _d_ 0.06.

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

Subgenus 2. _Cyrtocapsoma_, Haeckel.

_Definition._--Shell with four or more annular septa, and five or more joints.

8. _Cyrtocapsa incrassata_, Haeckel.

_Eucyrtidium incrassatum_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 105,
Taf. iv. fig. 9.

Shell rough, spindle-shaped, with four annular septa. Length of the five joints = 2 : 3 : 4 : 4 : 4. The third joint is the broadest, nearly three times as broad as long. The fourth joint is inversely conical, acute. Cephalis small, spherical, with two short, conical, divergent horns. Pores small, regular, circular.

_Dimensions._--Length of the shell (with five joints) 0.17, breadth 0.11. Length of the single joints, _a_ 0.015, _b_ 0.035, _c_ 0.04, _d_ 0.04, _e_ 0.04.

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

9. _Cyrtocapsa costata_, n. sp.

Shell smooth, spindle-shaped, twice as long as broad, with numerous longitudinal ribs, and four annular septa. Length of the five joints = 1 : 4 : 3 : 2 : 8. The third joint is the broadest. Fourth joint inversely conical, acute. Cephalis small, hemispherical, with a small conical horn. Pores regular, circular.

_Dimensions._--Length of the shell (with five joints) 0.18, breadth 0.09. Length of the single joints, _a_ 0.01, _b_ 0.04, _c_ 0.03, _d_ 0.02, _e_ 0.08.

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

10. _Cyrtocapsa colatractus_, n. sp.

Shell smooth, spindle-shaped, with eight internal annular septa (without external stricture). All nine joints are nearly equal in length, the first somewhat shorter, the last longer. The fourth joint is the broadest, four times as broad as long. Last joint inversely conical, blunt. Cephalis subspherical, with a conical horn of the same length. Pores small and numerous, regular, circular.

{1515}_Dimensions._--Length of the shell (with nine joints) 0.22, breadth 0.1; length of the cephalis 0.015, of the last joint, 0.03, of each of the seven other joints, 0.022 to 0.028.

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

11. _Cyrtocapsa chrysalidium,_ n. sp. (Pl. 76, fig. 9).

Shell rough, nearly spindle-shaped, with seven distinct strictures. Length of the eight joints = 4 : 6 : 11 : 8 : 5 : 5 : 4 : 3. The third and fourth joints are the broadest. The last joint is small, inversely cap-shaped. Cephalis subspherical, with an oblique, dentate horn of the same length. Pores very numerous, subregular, circular.

_Dimensions._--Length of the shell (with eight joints) 0.23, breadth 0.1. Length of the single joints, _a_ 0.02, _b_ 0.03, _c_ 0.055, _d_ 0.04, _e_ 0.025, _f_ 0.025, _g_ 0.02, _h_ 0.015.

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

Genus 654. _Stichocapsa_,[271] Haeckel, 1881, Prodromus, p. 439.

_Definition._--#Stichocapsida# (vel Stichocyrtida eradiata clausa) without apical horn, and without basal spine.

The genus _Stichocapsa_ differs from the preceding _Cyrtocapsa_ in the absence of an apical horn, and bears therefore to it the same relation as _Lithocampe_ does to _Eucyrtidium_. It may be derived either from _Cyrtocapsa_ by loss of the horn, or from _Eucyrtidium_ by closure of the terminal mouth.

1. _Stichocapsa tetracola,_ n. sp. (Pl. 78, fig. 1).

Shell smooth, spindle-shaped, half as broad as long, with three slight strictures. Length of the four joints = 3 : 4 : 4 : 11. The fourth joint is the broadest, inversely conical, with acute basal pole. Pores subregularly square in the second and third joints, more irregular in the fourth joint.

_Dimensions._--Length of the shell (with four joints) 0.11. Length of the single joints, _a_ 0.015, _b_ 0.02, _c_ 0.02, _d_ 0.055; breadth 0.055.

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

2. _Stichocapsa quadrigata,_ n. sp. (Pl. 78, fig. 3).

Shell smooth, pear-shaped, half as broad as long, with three deep strictures. Length of the four joints = 3 : 8 : 8 : 5. The second joint is the broadest. The fourth joint is scarcely larger than the hemispherical cephalis, inversely conical, with blunt basal pole. Pores subregular, square, in transverse rows, in the second and third joints of equal size, in the fourth smaller.

_Dimensions._--Length of the shell (with four joints) 0.12. Length of the single joints, _a_ 0.015, _b_ 0.04, _e_ 0.04, _d_ 0.025; breadth 0.06.

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

{1516}3. _Stichocapsa tricincta,_ n. sp. (Pl. 78, fig. 2).

Shell smooth, spindle-shaped, twice as long as broad, with three deep strictures. Length of the four joints = 2 : 5 : 5 : 10. The third joint is the broadest. Fourth joint inversely conical, with acute basal pole. Cephalis small, subconical. Pores irregular, roundish, of very different sizes.

_Dimensions._--Length of the shell 0.11. Length of the single joints, _a_ 0.01, _b_ 0.025, _e_ 0.025, _d_ 0.05; breadth 0.055.

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

4. _Stichocapsa subglobosa,_ n. sp.

Shell thorny, broad, pear-shaped, nearly spherical, almost as broad as long, with three internal septal rings. Length of the four joints = 1 : 2 : 7 : 2. Cephalis small, subspherical. Thorax flat, conical. Third joint very large, inflated, about twice as broad as the second and fourth joints. The latter is flat, cap-shaped, with rounded basal pole. Pores regular, circular, hexagonally framed, in the third joint twice as broad as in the second and fourth joints.

_Dimensions._--Length of the shell 0.24. Length of the single joints, _a_ 0.02, _b_ 0.04, _c_ 0.14, _d_ 0.04; breadth 0.2.

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

5. _Stichocapsa compressa,_ Haeckel.

_Lithocampe compressa_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 103, Taf.
iv. fig. 5.

Shell rough, broad, pear-shaped, almost as broad as long, with three internal septal rings. Length of the four joints = 1 : 2 : 3 : 2. Cephalis very small, spherical. Thorax conical. The third joint is the broadest, strongly inflated. The fourth joint (in the figure of Stöhr broken off) is in a well preserved specimen inversely hemispherical, with rounded basal pole. Pores very small, regular, circular.

_Dimensions._--Length of the shell 0.1. Length of the single joints, _a_ 0.013, _b_ 0.027, _c_ 0.04, _d_ 0.022; breadth 0.08.

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

6. _Stichocapsa pyriformis_, n. sp.

Shell rough, pear-shaped, about twice as long as broad, with three internal septal rings. Length of the four joints = 2 : 5 : 2 : 9. Cephalis small, spherical, hyaline. Thorax conical. Third joint very short and broad; the fourth joint is the broadest, half as long as the shell, with an inversely hemispherical basal pole. Pores subregular, circular, small and numerous, larger in the basal third.

_Dimensions._--Length of the shell 0.18. Length of the single joints, _a_ 0.02, _b_ 0.05, _c_ 0.02, _d_ 0.09; breadth 0.1.

_Habitat._--Fossil in Barbados.

{1517}7. _Stichocapsa monstrosa,_ n. sp. (Pl. 78, fig. 4).

Shell tuberculate, twice as long as broad, irregular, horn-shaped or inversely conical, with curved axis, and with three internal septal rings. Length of the four joints = 2 : 7 : 3 : 4. Cephalis subspherical, with small, circular pores. The thorax is the broadest joint, half as long as the shell. The fourth joint is small, inversely conical, with a blunt, curved, basal pole. Pores irregular, roundish, partly double-contoured.

_Dimensions._--Length of the shell (with four joints) 0.16. Length of the single joints, _a_ 0.02, _b_ 0.07, _c_ 0.03, _d_ 0.04; breadth 0.08.

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

8. _Stichocapsa pentacola_, n. sp. (Pl. 76, fig. 1).

Shell smooth, slender, pear-shaped, twice as long as broad, with four sharp strictures. Length of the five joints = 1 : 1 : 1 : 2 : 3. The three first joints are nearly equal in length, but increase in breadth. The fifth joint is the broadest, nearly spherical, with rounded basal pole. Pores irregular, roundish.

_Dimensions._--Length of the shell (with five joints) 0.13. Length of the single joints, _a_ 0.017, _b_ 0.017, _c_ 0.017, _d_ 0.028, _e_ 0.05; breadth 0.07.

_Habitat._--Central Pacific, Station 273, depth 2350 fathoms.

9. _Stichocapsa hexacola_, n. sp. (Pl. 76, fig. 2).

Shell rough, slender, pear-shaped, twice as long as broad, with five internal septal rings. The five first joints are nearly equal in length. The sixth joint is the broadest, half as long as the shell, with a rounded, hemispherical basal pole. Pores small and numerous, subregular, circular, larger in the inflated basal third.

_Dimensions._--Length of the shell (with six joints) 0.2. Length of each of the first five joints 0.02, of the sixth joint 0.1; breadth 0.1.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms; also fossil in Barbados.

10. _Stichocapsa compacta_, n. sp. (Pl. 76, fig. 3).

Shell rough very thick-walled, slender, pear-shaped, twice as long as broad, without external stricture, but with eight internal septal rings. The eight first joints, gradually increasing in breadth, are nearly equal in length. The eighth joint is the broadest, and one-third as long as the shell, inversely hemispherical. Pores small, circular, in the last joint larger.

_Dimensions._--Length of the shell (with nine joints) 0.25. Length of each of the eight first joints about 0.02, of the ninth joint 0.08; breadth 0.13.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms; also fossil in Barbados.

{1518}11. _Stichocapsa radicula,_ Haeckel.

_Lithocampe radicula_, Ehrenberg, 1838 (_partim_); Mikrogeol., 1854, Taf.
xxii. fig. 23_b_.?

Shell smooth, spindle-shaped, decreasing from the broader middle towards the two rounded poles, with four or five slight strictures. All five or six joints nearly equal in length, the middle (third and fourth) are the broadest. Pores subregular, circular. (To this species those forms of _Lithocampe radicula_, Ehrenberg, must be referred, in which the basal opening is perfectly closed by lattice-work. The other forms in which the basal mouth remains open, and which are connected with the former by transitional forms, constitute the true type of the genus _Lithocampe_ (page 1503).

_Dimensions._--Length of the shell (with six joints) 0.12 to 0.15, breadth 0.06 to 0.07.

_Habitat._--Fossil in Barbados.

12. _Stichocapsa subligata_, Haeckel.

_Lithocampe subligata_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 102, Taf.
iv. fig. 1.

Shell rough, subcylindrical, irregular, with seven slight strictures. All eight joints of slightly different lengths, the third joint is the broadest; the seventh joint is much broader than the sixth and the eighth joints. The latter is inversely hemispherical. Cephalis very small, spherical. Pores regular, circular, very small and numerous.

_Dimensions._--Length of the shell (with eight joints) 0.24; length of the single joints (on an average) 0.025 to 0.035, breadth 0.08.

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

13. _Stichocapsa paniscus_, n. sp. (Pl. 76, fig. 4).

Shell smooth, cylindrical, with a blunt, conical cephalis, and a hemispherical last joint, without external strictures, but with seven or eight internal septa. Eight or nine joints nearly equal in length, the second and the last somewhat longer. Pores circular, of unequal sizes.

_Dimensions._--Length of the shell (with seven joints) 0.16; length of each joint (on an average) 0.02 to 0.03, breadth 0.07.

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

14. _Stichocapsa cylindrica_, n. sp.

Shell rough, cylindrical, four times as long as broad, with hemispherical cephalis and last joint, without external stricture, but with ten or eleven internal septa. All eleven or twelve joints are nearly equal in length, and are three times as broad as long. Only the flat cephalis is shorter, and the vaulted last joint longer than each of the nine or ten other joints. Pores regular, circular.

_Dimensions._--Length of the shell (with twelve joints) 0.24; length of each joint (on an average) 0.02, breadth 0.06.

_Habitat._--Tropical Atlantic, Station 338, depth 1990 fathoms.

{1519}Genus 655. _Artocapsa_,[272] Haeckel, 1881, Prodromus, p. 438.

_Definition._--#Stichocapsida# (vel Stichocyrtida eradiata clausa) with an apical horn on the cephalis, and a basal terminal spine on the last joint.

The genus _Artocapsa_ differs from _Cyrtocapsa_, its ancestral form, by the development of a vertical terminal spine, or a bunch of spines, on the base of the last joint, and bears therefore to it the same relation as _Rhopalatractus_ does to _Rhopalocanium_.

1. _Artocapsa fusiformis_, n. sp. (Pl. 76, fig. 5).

Shell spindle-shaped, rough, with five slight strictures, decreasing uniformly from the broader middle towards both poles, with a strong, pyramidal, terminal spine at each pole. Length of the six joints = 2 : 5 : 3 : 3 : 2 : 5. Cephalis hemispherical, hyaline, without pores, its horn half as large as the basal spine. Pores small and numerous, subregular, circular.

_Dimensions._--Length of the shell (with six joints) 0.2, breadth 0.09. Length of the single joints, _a_ 0.02, _b_ 0.05, _c_ 0.03, _d_ 0.03, _e_ 0.02, _f_ 0.05.

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

2. _Artocapsa spinosa_, n. sp. (Pl. 76, fig. 10).

Shell spindle-shaped, spiny, with five distinct strictures. Length of the six joints = 2 : 3 : 2 : 5 : 4 : 4. The fourth joint is the broadest, and much larger than the five other joints. The first and the last joints are similar in size and form, hemispherical, armed with some larger, irregular, conical spines. Pores irregular, roundish, of variable sizes.

_Dimensions._--Length of the shell (with six joints) 0.2, breadth 0.09. Length of the single joints, _a_ 0.02, _b_ 0.03, _c_ 0.02, _d_ 0.05, _e_ 0.04, _f_ 0.04.

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

3. _Artocapsa infraculeata_, Haeckel.

_Eucyrtidium infraculeatum_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 106,
Taf. iv. fig. 13.

Shell subcylindrical, rough, with five annular septa. Length of the six joints = 2 : 3 : 4 : 4 : 4 : 3. The third, fourth, and fifth joints are nearly equal in length and breadth, whilst the second and sixth are cupola-shaped. The cephalis is very small, subspherical (regarded by Stöhr as a "large pore"), and bears a short conical horn. The last joint bears a bunch of basal spines.

_Dimensions._--Length of the shell (with six joints) 0.2, breadth 0.09. Length of the cephalis 0.02, second and sixth joints 0.03, third, fourth, and fifth joints 0.04.

_Habitat._--Fossil in Tertiary rocks of Sicily; Grotte (Stöhr), Caltanisetta (Haeckel).

{1520}4. _Artocapsa quadricamera_, n. sp.

Shell spindle-shaped, smooth, with three sharp strictures. Length of the four joints = 2 : 3 : 4 : 8. The third joint is the broadest. The fourth joint is inversely conical, nearly as long as the three other joints together, and bears a strong, conical, basal spine, of half the length. The cephalis is small, subspherical, and bears a conical horn of the same length. Pores subregular, circular.

_Dimensions._--Length of the shell (with four joints) 0.17, breadth 0.08. Length of the single joints, _a_ 0.02, _b_ 0.03, _c_ 0.04, _d_ 0.08.

_Habitat._--Fossil in Barbados.

5. _Artocapsa armata_, n. sp.

Shell slender, inversely ovate, spiny, with six deep strictures. Length of the seven joints = 2 : 4 : 6 : 5 : 4 : 3 : 2. The third joint is the broadest, inflated, and much larger than the four following, which gradually decrease in size. The small, hemispherical cephalis bears a stout pyramidal horn of twice the length. The last hemispherical joint is armed with a bunch of stout spines, one of which is much the larger, and as long as the third joint. Pores irregular, roundish.

_Dimensions._--Length of the shell (with seven joints) 0.26, breadth 0.12. Length of the single joints, _a_ 0.02, _b_ 0.04, _c_ 0.06, _d_ 0.05, _e_ 0.04, _f_ 0.03, _g_ 0.02.

_Habitat._--Western Tropical Pacific, Station 225, depth 4575 fathoms.

6. _Artocapsa octocamera_, n. sp.

Shell subcylindrical, smooth, with seven internal annular septa. Five joints (the third to the seventh) are nearly equal in size, while the second and eighth are cupola-shaped, somewhat longer. The cephalis is smaller, with a conical horn of the same length. The last joint bears a bunch of divergent, conical spines, of different lengths. Pores small, regular, circular.

_Dimensions._--Length of the shell (with eight joints) 0.16, breadth 0.08. Length of the cephalis 0.016, second and eighth joints 0.033, each of the five other joints 0.022.

_Habitat._--South Pacific, Station 285, depth 2375 fathoms.

7. _Artocapsa elegans_, n. sp. (Pl. 76, fig. 8).

Shell spindle-shaped, smooth, with eight internal, broad, annular septa. The second and third joints are the largest, the fourth and fifth of medium size, while the cephalis and the four last joints are nearly equal in length, and much shorter. The third joint is the largest. The subspherical cephalis bears a bristle-shaped horn of the same length, while the last joint is armed with a bunch of conical spines. Pores small, in the upper half of the shell regular, hexagonal, in the lower half irregular.

_Dimensions._--Length of the shell (with nine joints) 0.2, breadth 0.09. Length of the first and the four last joints, each 0.014; of the fourth and fifth, each 0.02; of the third 0.04, second 0.05.

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

{1521}LEGION IV. PHÆODARIA,

VEL CANNOPYLEA, VEL PANSOLENIA (PLS. 99-128).

_Phæodaria_, Haeckel, 1879.
_Tripylea_, Hertwig, 1879.
_Cannopylea_, Haeckel, 1881.
_Pansolenia_, Haeckel, 1878.

_Definition._--Radiolaria with a double membrane surrounding the central capsule, which bears on one pole of the main axis a peculiar astropyle, or a tubular main-opening, in the centre of a circular radiate operculum. Usually (but not constantly) a pair of small, lateral, accessory openings (or parapylæ) on the opposite pole of the main axis. Extracapsulum constantly with a phæodium, or with a voluminous aggregation of peculiar dark pigment bodies (phæodella) covering the astropyle of the central capsule. Skeleton siliceous or silicated, always extracapsular, very rarely wanting. Fundamental form very variable, originally monaxon, often dipleuric or bilateral.

The legion PHÆODARIA, or CANNOPYLEA, in the extent here defined, was constituted by me in 1878, in my Protistenreich (p. 102) under the name PANSOLENIA. This name was given on the supposition that the skeleton of these interesting Radiolaria is always composed of hollow tubules, in contrast to that of the other Radiolaria, where it is never tubular. But I was soon convinced that this supposition was erroneous, that in a great part of the PANSOLENIA the skeleton is not composed of hollow tubules but of solid bars, and that a constant, very characteristic, and never failing mark of this group is to be found in the peculiar phæodium, a voluminous, constant, extracapsular pigment body. Therefore, in 1879, I changed the name into PHÆODARIA, and having discovered in the collection of the Challenger an astonishing number of new and wonderful types of this group, I described, in a preliminary note on it, four different orders and ten families with thirty-eight genera (Ueber die Phæodarien, eine neue Gruppe kieselschaliger mariner Rhizopoden; in Sitzungsberichte der Jenaischen Gesellschaft für Medicin und Naturwissenschaft. Sitzung vom 12th December 1879).

In the same year (1879), Richard Hertwig, in his excellent work entitled Der Organismus der Radiolarien, published the first accurate description of the intimate structure of the soft body of the PANSOLENIA, and mainly of their central capsule; and having always observed, in the few representatives examined by him, three openings in the capsule (one main-opening and two accessory openings), he called them TRIPYLEA (_loc. cit._ p. 87), being guided by the erroneous supposition that these three openings are {1522}constant in all members of the group. But this is by no means the case. The two accessory openings are completely absent in several families, whilst in others their number is increased. A constant and very striking character, however, of all PHÆODARIA, is the peculiar structure of their tubular main-opening, which I call astropyle, with its radiate operculum and cannular proboscis. On account of this important and startling characteristic I proposed in 1881 to call this group CANNOPYLEA. The two names PHÆODARIA and CANNOPYLEA both express a very striking and quite constant character of these curious Radiolaria, whilst the two names PANSOLENIA and TRIPYLEA are applicable only to a part of the whole legion.

The history of our knowledge of the PHÆODARIA is short, but very remarkable. Although hundreds of species, many of them cosmopolitan, are distributed over all oceans and all zones, although their size is in general much greater than that of the other Radiolaria (usually 1 to 2 mm., often even 5 to 10 mm. or more), and although their form and structure are usually striking, nevertheless the PHÆODARIA remained completely unknown up to the year 1859. During that year I observed the first forms living in the Gulf of Messina, and described and figured in 1862 in my Monograph five genera and seven species, viz., (1) _Aulacantha scolymantha_ (p. 263), (2) _Thalassoplancta cavispicula_ (p. 261, now _Cannobelos cavispicula_), (3) _Aulosphæra trigonopa_, and _Aulosphæra elegantissima_ (p. 359), (4) _Spongodictyum trigonizon_ (p. 459, now _Sagoplegma trigonizon_), and (5) _Coelodendrum ramosissimum_, and _Coelodendrum gracillimum_ (p. 361). I recognised the structure of the three genera enumerated as 1, 3, and 5, as so remarkable and so different from that of the other Radiolaria, that I founded three peculiar families for them, the Aulacanthida, Aulosphærida, and Coelodendrida.

The first note on the numerous remarkable PHÆODARIA discovered by the Challenger, and mainly on the large-sized inhabitants of the deep-sea, was published in 1876 by Dr. John Murray, in his Preliminary Reports on Work done on Board the Challenger (Proc. Roy. Soc., vol. xxiv., read March 16, 1876). He pointed out (_loc. cit._, p. 535), that the tow-nets, sent down to a great depth (according to a new plan, adopted in April 1875) brought up on every occasion a great many new and peculiar Rhizopods, which had never been observed in the nets used near the surface. "The shells of all have an exceedingly beautiful tracery, a fenestrated appearance often, which a closer examination shows to be caused by pit-like depressions. Some have only one, others have several openings, through which the sarcode flows. The sarcode of all these deep-sea Rhizopods has many large black-brown pigment-cells. At times they come up with a good deal of the sarcode outside of the shell; and two specimens have been seen to throw out elongated pseudopodia" (_loc. cit._, p. 536). Dr. John Murray distinguished at that time not less than fifty species of these interesting deep-sea Rhizopods and called them provisionally Challengerida; a term which we retain here for the largest and most characteristic family. He gave at the same time, in an accompanying plate (xxiv.), six {1523}figures of new PHÆODARIA, the names of which (as found by me in 1879 in the corresponding preparations) are the following; (1) _Challengeria naresii_, (2) _Challengeria aldrichii_, (3) _Bivalva compressa_ (now = _Conchopsis compressa_), (4) _Tuscarora belknapii_, (5) _Challengeria circopora_ (now = _Circoporus sexfurcus_), and (6) _Haeckeliana porcellana_. A great number of these Challengerida (twenty species) were afterwards figured by Dr. John Murray in the Narrative of the Cruise of H.M.S. Challenger, 1885, vol. i. part 1, p. 226, Pl. A; viz., fourteen species of _Challengeria_ and six species of _Tuscarora_.

The most important advance in the knowledge which we had of the peculiar organisation of the PHÆODARIA, was made by the accurate description which Richard Hertwig published, in 1879, of the intimate structure of their central capsule, and mainly of its peculiar openings. He examined living at Messina the following three forms, described in my Monograph; (1) _Aulacantha scolymantha_, (2) _Aulosphæra elegantissima_, and (3) _Coelodendrum ramosissimum_. Besides, he described an interesting new genus, _Coelacantha anchorata_; and another new form, which he placed in the Aulosphærida, as _Aulosphæra gracilis_, but which really was a new genus of Sagosphærida, here described as _Sagoscena gracilis_. Finally, Hertwig first discovered that the peculiar bodies, described by Ehrenberg as _Dictyocha_ and placed by him in the _Diatomea_ (_Polygastrica_), were the isolated pieces of the skeleton of a true _Phæodarium_, and that they were scattered loosely in great numbers over the surface of the jelly-sphere, just as are the hollow spicula of _Thalassoplancta_ or _Cannobelos_.

The six species mentioned, of which Hertwig gave a very accurate description and very instructive figures, belong to six different genera, and these represent six different families of PHÆODARIA, viz.; Aulacanthida, Aulosphærida, Coelodendrida, Cannosphærida, Sagosphærida and Cannorrhaphida. He found that all these six forms, in spite of great differences in the form and structure of their skeleton, were identical in the structure of the central capsule; and since he observed constantly three openings in its double wall (a large main-opening on the oral pole, and a pair of lateral accessory openings on the aboral pole of its main axis) he called them TRIPYLEA (_loc. cit._, p. 87, 94). But he also pointed out the remarkable shape of their voluminous extracapsular body, and especially the characteristic position, size, colour and composition of the large pigment body, which I had called the phæodium.

The accurate description of the gigantic and elegant skeleton of a new _Phæodarium_, surpassing all other known Radiolaria in its extraordinary size (15 mm.), was published in 1882 by O. Bütschli (in Zeitschr. f. wiss. Zool., vol. xxxvi. p. 486, Taf. xxxi.). He called it _Coelothamnus davidoffii_, in honour of its discoverer, who had found it floating on the surface of the Gulf of Villafranca, near Nice. He placed it among the Coelodendrida; it belongs, however, to that part of this group which possesses a nasal tube, and which I afterwards separated under the name Coelographida.

{1524}The total number of PHÆODARIA, hitherto described and illustrated by figures, amounts therefore to seventeen species, viz., the seven species first described by myself (in 1862); the six new species figured by Dr. John Murray (in 1876); the three new species discovered by Hertwig (in 1879) and the single species last-mentioned described by Bütschli (in 1882). The rich collection of the Challenger has added to this small number such an astonishing wealth of new and remarkable forms, that I can describe in the following system of PHÆODARIA not less than eighty-four genera and four hundred and sixty-five species. These belong to fifteen different families and four different orders. But this great number is probably only a small part of the numerous interesting PHÆODARIA, which are abundantly distributed over all the oceans; those (_e.g._) of the Indian and of the Arctic Oceans are almost unknown.

The great majority of these wonderful PHÆODARIA are inhabitants of the deep-sea, mainly of the southern hemisphere, and are so common in many stations explored by the Challenger, that its collection contains many thousands (or rather hundreds of thousands) of well-preserved specimens. A smaller part of the legion is found on the surface, widely distributed over all oceans; some of these are very common (as, _e.g._, _Aulacantha_, _Aulosphæra_, _Sagosphæra_, _Coelodendrum_, _Castanella_, &c.) and it is difficult to explain how they could entirely escape the eyes of all former observers.

The three general characters which distinguish the PHÆODARIA easily and constantly from all the other Radiolaria are the following:--(1) the double membrane, a thick outer and a thin inner envelope, of the big central capsule; (2) its typical main-opening or astropyle, placed on the oral pole of the main axis, and distinguished by a peculiar radiate operculum, with tubular proboscis; (3) the phæodium, or the peculiar voluminous pigment-body, which constantly lies in the oral half of the calymma, surrounds the oral part of the central capsule, and is composed of numerous phæodella, or singular pigment-granules of green, olive, brown or black colour.

Besides these three general and never failing marks of the PHÆODARIA, the majority of this legion (but by no means all) possess the three following peculiarities; (1) two parapylæ or accessory openings of the central capsule, placed laterally (at the right and left) on the aboral pole of the main axis (wanting in the Challengerida, Medusettida, Castanellida, and perhaps in some other families); (2) a characteristic skeleton which is always extracapsular, wanting only in the Phæodinida, incomplete in the Cannorrhaphida and Aulacanthida, but perfectly developed and of very various shapes in the twelve other families; usually this silicated skeleton is composed of hollow tubules, which are filled up by jelly (PANSOLENIA); but in some families it is composed of ordinary solid network, not different from that of the other Radiolaria, _e.g._, especially in the Castanellida and Sagosphærida; (3) an extraordinary size of the body, as well of the central capsule and its nucleus, as of the extracapsular skeleton; the majority of PHÆODARIA have a diameter of 1 to 2 mm., and are therefore from ten to twenty times as large as the {1525}majority of the other Radiolaria; in some gigantic forms the diameter of the unicellular body reaches 20 or even 30 mm.

_The Central Capsule_ of the PHÆODARIA is the most important part of their body and preserves in all families of this legion the same essential structure, and nearly the same form, in striking contrast to the extraordinary variety and complication of the skeleton. As already mentioned, it differs from the central capsule of all the other Radiolaria in two most important peculiarities; firstly, the double membrane of the spheroidal capsule, and secondly, the singular structure of its constant main-opening, the astropyle. A third constant character is the considerable size of the enclosed nucleus, the diameter of which usually equals about half of that of the capsule itself.

The diameter of the capsule is, in the majority of PHÆODARIA, 0.1 to 0.2 mm., often also 0.3 to 0.4, rarely more than 0.5, or less than 0.05 mm.

The position of the central capsule is somewhat different in the four orders into which we have divided the PHÆODARIA. It lies in the centre of the spherical, concentric calymma in all the #Phæocystina#, or in those PHÆODARIA which possess no complete lattice-shell--Phæodinida, Cannorrhaphida, and Aulacanthida (Pls. 101-105). The #Phæosphæria# (comprising the Orosphærida, Sagosphærida, Aulosphærida, and Cannosphærida, Pls. 106-112) all possess a very big, usually spherical lattice-shell, and here the central capsule is much smaller than the latter and lies in its centre. Another position is constantly occupied by the central capsule in all #Phæogromia# (Pls. 99, 100, 113-120; the families Challengerida, Medusettida, Castanellida, Circoporida, Tuscarorida), which have a peculiar mouth on the lattice-shell, placed on the oral pole of its main axis; the central capsule lies in the opposite aboral half of the shell cavity. The #Phæoconchia# finally (Pls. 121-128, the families Concharida, Coelodendrida, and Coelographida) all possess a bivalved shell, and the capsule is here enclosed between the two valves of the shell.

The form of the central capsule is constantly spheroidal, slightly depressed in the direction of the main axis, and therefore comparable to the spheroidal form of our globe. The depression is generally very slight, so that the proportion of the minor vertical main axis to the major horizontal or equatorial axis is about 4 : 5 or 5 : 6, often even 8 : 9 or less; but sometimes the proportion becomes 3 : 4, or even 2 : 3, so that the capsule becomes nearly lenticular; very rarely its form becomes almost perfectly spherical (Pl. 101, fig. 1). The main axis stands always vertically, and is distinctly marked by the peculiar shape of the astropyle, placed on its oral pole. Usually this pole, in the living and freely floating PHÆODARIA seems to be the lower pole, directed downwards (as also in the NASSELLARIA); but in some families it seems to be inversely directed upwards, as in the Challengerida and Tuscarorida, (Pls. 99, 100).

The two _membranes of the central capsule_ possess in all PHÆODARIA a very different shape, and were in all preparations which I could accurately examine (some hundreds {1526}belonging to all families) separated by a clear, rather wide interval, filled up either by a colourless fluid or by a structureless jelly (Pl. 103, fig. 1; Pl. 123, figs. 8, 9, &c.). They are in direct connection only at the openings. In the living PHÆODARIA, however, their distance is very small, or they are in immediate contact without any interval (Pl. 101, fig. 10; Pl. 102, fig. 1). According to the observations of Hertwig, the two membranes are always in close contact, and without interspace, in the living PHÆODARIA; and the space between them is an artificial product due to the influence of the preserving fluid or of certain chemical agents. In every case it is very easy to separate both membranes completely, except at the openings, where they are in direct connection. We distinguish both membranes shortly as ectocapsa and endocapsa.

The ectocapsa, or the outer membrane of the central capsule, is rather firm and durable, double-contoured, elastic and difficult to destroy. Its physical and chemical qualities seem to approach those of chitin. It becomes, however, stained red by carmine, and yellow by nitric acid. Usually it appears structureless and refracts the light strongly. In a few cases, however, it exhibits, when examined by strong lenses, a fine punctation; and in some Aulacanthida (especially in some big forms of _Aulographis_ and _Aulospathis_) the entire ectocapsa was densely covered with peculiar curved, or S-shaped dark corpuscles (Pl. 114, fig. 13). They were all of the same length, about 0.01, and seemed to lie on its inner face.

The endocapsa, or the inner membrane of the central capsule, is much thinner than the outer, with which it is in immediate connection only at the openings. It encloses the entire contents of the capsule, and becomes very distinct, as soon as the latter are dissolved by chemical agents, or stained by carmine. In the majority of well-preserved preparations it is irregularly plicated, and resembles a thin, but firm, crumpled paper. Isolated pieces of the endocapsa are completely structureless, but exhibit also a considerable resistance, in spite of their minute thickness.

The openings of the central capsule exhibit in the PHÆODARIA a greater variety than their discoverer, R. Hertwig, supposed. The majority of the legion, certainly, possess the three openings described by him, and are therefore true TRIPYLEA. Some families, however, have only one opening, the astropyle, which is generally present (Challengerida, Medusettida, Castanellida, and _Phæocolla_ among the Phæodinida, Pl. 101, fig. 1). In some other families there is a variable number of accessory openings or parapylæ, one, three, or more, _e.g._, especially in the Circoporida and Tuscarorida. The former may be called Astropylea, the latter Sporopylea. Thus only a single opening to the central capsule is constant in all PHÆODARIA without exception, and that is the astropyle, or the large main-opening with its peculiar structure.

The astropyle, or the single constant main-opening of the central capsule, is distinguished by a very remarkable structure, and is sufficient of itself to separate the {1527}PHÆODARIA from all the other Radiolaria, and from the other Rhizopoda in general. It is always placed on the oral pole of the main axis, forming here a peculiar cap-shaped or flatly conical elevation, the centre of which is prolonged into a short, cylindrical tubule; we call the latter shortly a proboscis, and the former an operculum. To understand better the different forms which these important parts assume in the different families, compare Pl. 101, figs. 1-6; Pl. 102, fig. 1; Pl. 103, fig. 1; Pl. 104, figs. 1-3; Pl. 111, fig. 2; Pl. 123, figs. 1-9; Pl. 127, figs. 4-6; Pl. 128, fig. 2, &c. Compare also the first very accurate figures which R. Hertwig has given in 1879 (_loc. cit._) in his Taf. x.