2. Botryopyle cribrosa, Haeckel.

Cephalis trilobate, separated by a slight collar constriction from the ovate thorax, which is somewhat smaller. Occipital lobe very large, helmet-shaped, longer than the thorax and twice as long as the two subspherical frontal lobes. Pores regular, circular, scarce.

Dimensions.—Length of the shell 0.11, breadth 0.05.

Habitat.—Fossil in Barbados.

3. Botryopyle cephalodes, Haeckel.

Cephalis quinquelobate, separated by a slight collar constriction from the larger conical thorax, which is gradually dilated towards the wide mouth. Occipital lobe helmet-shaped, little longer than the frontal half of the cephalis, which is divided into two pairs of lateral chambers, corresponding to the four crossed pores of the sagittal septum, figured by Ehrenberg. The figure of the latter is inverse, seen from the frontal face, a part of the frontal wall having been broken off.

Dimensions.—Length of the shell 0.08, breadth 0.05.

Habitat.—Fossil in Barbados.

4. Botryopyle dictyocephalus, n. sp. (Pl. 96, fig. 6).

Cephalis multilobate, separated by an oblique constriction from the subcylindrical thorax, which is somewhat larger and slightly curved. Occipital lobe conical, of the same length as the posterior part of the triangular frontal half of the shell, which is divided into five to seven lobes, two or three odd lobes in the median part, and one or two pairs of lateral lobes; very variable in size and form of the lobes. Mouth of the thorax wide, truncate.

Dimensions.—Length of the shell 0.12, breadth 0.07.

Habitat.—Central Pacific, Station 271 to 274, depth 2350 to 2750 fathoms.

5. Botryopyle inclusa, n. sp. (Pl. 96, fig. 5).

Cephalis multilobate, campanulate, separated by a sharp constriction from the inflated thorax, which is nearly twice as long and broad. Both joints of the shell are irregularly lobate, with numerous vaulted lobes of different sizes, and partly internal septa. Pores small and numerous.

Dimensions.—Length of the shell 0.1, breadth 0.06.

Habitat.—Mediterranean (Candia), Spratt, depth 1620 fathoms.

Genus 489. Acrobotrys, Haeckel,^[106] 1881, Prodromus, p. 440.

Definition.—Lithobotryida with tubes on the cephalis, and with the mouth of the thorax open.

The genus Acrobotrys differs from the preceding Botryopyle in the development of radial tubes, and from its probable ancestral form, Cannobotrys, in the development of a thorax, the basal mouth of which remains open. According to the varying number of the tubes we may distinguish the following five subgenera (corresponding to those of Cannobotrys), viz., (1) Acrobotrantha (monosolenia) with a single (apical) tube; (2) Acrobotrella (disolenia) with two divergent tubes (an apical and a sternal); (3) Acrobotrissa (trisolenia) with three sagittal tubes (an apical, a caudal, and a sternal); (4) Acrobotromma (tetrasolenia) with four tubes, like the four typical spines of Cortina; and (5) Acrobotrusa (pentasolenia) with five feet, corresponding to the five typical spines of Stephanium.

1. Acrobotrys monosolenia, n. sp.

Cephalis trilobate, with a single straight apical tube, which ascends vertically from the apex of the occipital lobe, and is pointed at the distal end, with an anterior oblique aperture. Two frontal lobes paired, ovate, half as long as the helmet-shaped occipital lobe. Thorax ovate, twice as long as the cephalis. Pores very scarce.

Dimensions.—Length of the shell 0.08, breadth 0.06.

Habitat.—Mediterranean (Corfu), surface.

2. Acrobotrys disolenia, n. sp. (Pl. 96, fig. 10).

Cephalis trilobate, with three odd ovate lobes of nearly equal size in the sagittal plane and two divergent straight slender cylindrical tubes, a vertical apical tube on the occipital lobe, and a horizontal nasal tube on the frontal lobe; the middle lobe between them is somewhat smaller. Thorax ovate, about twice as large as the cephalis, with constricted mouth. Pores small and numerous.

Dimensions.—Length of the shell 0.1, breadth 0.06.

Habitat.—Central Pacific, Station 265 to 274, depth 2350 to 2925 fathoms.

3. Acrobotrys aquaria, n. sp.

Cephalis quinquelobate, with two divergent long cylindrical curved tubes. Occipital lobe helmet-shaped, with an ascending apical tube; nasal lobe conical, with a descending sternal tube; between them a smaller odd middle lobe, and on each side of the latter an ovate frontal lobe. Thorax inflate, twice as long and broad as the cephalis. Pores small, scarce.

Dimensions.—Length of the shell 0.09, breadth 0.07.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

4. Acrobotrys acuminata, n. sp. (Pl. 96, fig. 9).

Cephalis sexlobate, with two divergent tubes. Occipital and frontal lobes ovate, odd; between them a cupola-shaped apical lobe, bearing an ascending pointed apical tube. On each side at the base a small buccal lobe, and between the paired buccal lobes an anterior nasal lobe with a descending curved sternal tube. Thorax smaller than the cephalis. Pores numerous and small.

Dimensions.—Length of the shell 0.11, breadth 0.09.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

5. Acrobotrys auriculata, n. sp. (Pl. 96, fig. 11).

Cephalis quadrilobate, with three pointed and auriculate tubes, two ascending apical (an anterior and a posterior) in the helmet-shaped occipital lobe, and a descending sternal tube on the base of the frontal lobe; between the lobes two lateral paired buccal lobes. Thorax campanulate, twice as broad as the cephalis. Pores rather large and numerous.

Dimensions.—Length of the shell 0.1, breadth 0.08.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

6. Acrobotrys trisolenia, n. sp. (Pl. 96, fig. 8).

Cephalis quadrilobate, with four odd lobes and three divergent curved tubes, an ascending apical tube in the conical occipital lobe, and two descending tubes on the anterior and posterior basal lobes; between these three lobes a small central lobe. Thorax ovate, about as large as the cephalis. Pores small and numerous.

Dimensions.—Length of the shell 0.11, breadth 0.05.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

7. Acrobotrys tetrasolenia, n. sp.

Cephalis trilobate, with four slender cylindrical tubes. Occipital lobe helmet-shaped, with an apical tube on the apex and a caudal tube on the base. Two frontal lobes ovate, prolonged into two paired pectoral tubes. The four tubes correspond in position to the four spines of Cortina. Thorax inflate, ovate, larger than the cephalis. Pores very scarce, rather large, irregular.

Dimensions.—Length of the shell 0.08, breadth 0.05.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

8. Acrobotrys pentasolenia, n. sp.

Cephalis quinquelobate, with five short conical tubes; three divergent odd tubes arise from three odd lobes; an apical from the occipital lobe, a posterior caudal from the suboccipital lobe, and an anterior sternal from the nasal lobe. Two paired lateral tubes arise from the base of two ovate frontal lobes. The five tubes correspond in disposition to the five spines of Stephanium. Thorax truncate. Pores small.

Dimensions.—Length of the shell 0.12, breadth 0.09.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

Genus 490. Botryocella,^[107] Haeckel, 1881, Prodromus, p. 440.

Definition.—Lithobotryida without tubes on the cephalis, and with the mouth of the thorax closed.

The genus Botryocella differs from the closely allied Botryopyle in having the mouth of the thorax closed, and may be derived from it by development of a lattice-plate, effecting this closure. It bears therefore the same relation to the latter that Dicolocapsa has to Dictyocephalus.

1. Botryocella nucula, Haeckel.

Cephalis trilobate; occipital lobe helmet-shaped, nearly twice as long as the two ovate frontal lobes. Thorax about as long as the cephalis. Pores very small and scarce.

Dimensions.—Length of the shell 0.06, breadth 0.03.

Habitat.—Fossil in Barbados.

2. Botryocella borealis, Haeckel.

Cephalis trilobate; occipital lobe ovate, little longer than the two ovate frontal lobes. Thorax about twice as long as the cephalis. Pores very numerous and small.

Dimensions.—Length of the shell 0.08, breadth 0.04.

Habitat.—North Atlantic, Greenland, depth 1000 to 2000 fathoms.

3. Botryocella tricellaris, n. sp.

Cephalis trilobate, with three odd sagittal lobes; the middle or central lobe larger than the anterior frontal and smaller than the posterior occipital lobe. Thorax nearly spherical, about as long as the cephalis. Pores small and scarce.

Dimensions.—Length of the shell 0.08, breadth 0.06.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

4. Botryocella quadricellaris, n. sp. (Pl. 96, fig. 13).

Cephalis quadrilobate; the helmet-shaped occipital lobe twice as long as the two paired subspherical buccal lobes, and three times as long as the odd spherical frontal lobe. Thorax nearly spherical, about as long as the cephalis.

Dimensions.—Length of the shell 0.1, breadth 0.05.

Habitat.—Central Pacific, Station 272, depth 4475 fathoms.

5. Botryocella quadrigemina, n. sp. (Pl. 96, fig. 14).

Cephalis quadrilobate, with two pairs of lateral ovate lobes and complete sagittal constriction; the two occipital lobes nearly twice as large as the two frontal lobes. Thorax ovate, separated from the cephalis by a collar septum with four cortinar pores (fig. 14).

Dimensions.—Length of the shell 0.09, breadth 0.06.

Habitat.—Indian Ocean, Sunda Strait (Rabbe), surface.

6. Botryocella multicellaris, n. sp. (Pl. 96, fig. 12).

Cephalis multilobate; occipital lobe helmet-shaped, very large, about twice as long and broad as the frontal half of the shell, which is divided into six to eight small roundish clustered lobes. Thorax subspherical, of about the same size as the cephalis.

Dimensions.—Length of the shell 0.1, breadth 0.05.

Habitat.—South Pacific Station 297, depth 1775 fathoms.

Genus 491. Lithobotrys,^[108] Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 74.

Definition.—Lithobotryida with tubes on the cephalis, and with the mouth of the thorax closed.

The genus Lithobotrys, the oldest and first known of the Botryodea, was founded by Ehrenberg in 1844, and was one of his five oldest genera of Polycystina. It represented by itself the suborder Botryodea until the year 1860. The numerous species described by Ehrenberg belong to very different genera of Botryodea, and partly also of Spyroidea. Following Bütschli (1882) we retain here the name Lithobotrys for those species, the type of which is Lithobotrys geminata. The genus Lithocorythium of Ehrenberg is for the greater part identical with it. When in the preceding genus Acrobotrys the mouth of the thorax becomes closed by lattice work, Lithobotrys arises. In the latter as well as in the former the number of tubes on the cephalis is different, and may characterise different subgenera.

1. Lithobotrys geminata, Ehrenberg.

Cephalis trilobate, with a single apical tube in the apex of the helmet-shaped occipital lobe, which is one and a half times as long as the two subspherical frontal lobes. Thorax ovate, one and a half times as long as the cephalis, with few small pores in six to eight transverse rows.

Dimensions.—Length of the shell 0.1, breadth 0.05.

Habitat.—Fossil in Barbados.

2. Lithobotrys lithocorythium, Haeckel.

Cephalis trilobate, with a single apical horn or a pointed tube in the apex of the helmet-shaped occipital lobe, which is a little longer than the two ovate frontal lobes. Thorax ovate, about as long as the cephalis, with very numerous and small pores.

Dimensions.—Length of the shell 0.08, breadth 0.04.

Habitat.—Fossil in Barbados.

3. Lithobotrys nasuta, Ehrenberg.

Cephalis quadrilobate, with a single descending sternal or nasal tube on the base of the anterior or frontal lobe, which is half as long as the helmet-shaped occipital lobe and twice as large as the two lateral buccal lobes. Thorax ovate, twice as long as the cephalis. Pores rather large, circular.

Dimensions.—Length of the shell 0.11, broad 0.05.

Habitat.—Fossil in Barbados.

4. Lithobotrys ornata, Ehrenberg.

Cephalis quinquelobate, with two divergent ascending tubes, a posterior occipital and an anterior sternal or nasal tube. Occipital lobe campanulate, twice as large as the two frontal, and four times as large as the two buccal lobes. Thorax ovate, twice as long as the cephalis. Pores scarce and small. The specimen figured by Ehrenberg is very incomplete.

Dimensions.—Length of the shell 0.09, breadth 0.05.

Habitat.—Fossil in Barbados.

5. Lithobotrys sphærothorax, n. sp. (Pl. 96, fig. 15).

Cephalis trilobate, with two divergent cylindrical tubes, an ascending apical tube in the apex of the ovate occipital lobe, and a descending sternal or nasal tube in the campanulate frontal lobe; between the two lobes a smaller central lobe. Thorax spherical, twice as long as the latter. Pores very small, numerous.

Dimensions.—Length of the shell 0.08, breadth 0.06.

Habitat.—Western Tropical Pacific, Station 225, depth 4575 fathoms.

6. Lithobotrys mascula, n. sp. (Pl. 96, fig. 16).

Cephalis sexlobate, with two divergent cylindrical tubes, an ascending apical tube in the apex of the helmet-shaped occipital lobe and a descending sternal tube on the base, between the two kidney-shaped frontal lobes. The latter are half as large as the odd occipital lobe and of about the same size as the two inflated lateral buccal lobes, which are separated by a small odd nasal lobe.

Dimensions.—Length of the shell 0.13, breadth 0.08.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

7. Lithobotrys orchidea, n. sp. (Pl. 96, fig. 17).

Cephalis sexlobate, similar to the preceding species, but with five divergent and curved cylindrical tubes, which correspond to the five spines of Stephanium; an apical tube on the apex of the occipital lobe, a caudal tube on its base, a sternal tube between the two frontal lobes, and two paired pectoral tubes between the latter and the lateral buccal lobes. Pores small and scarce.

Dimensions.—Length of the shell 0.12, breadth 0.06.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Family LVIII. Pylobotryida, Haeckel (sensu emendato).

Definition.—Botryodea trithalamia, the shell of which is composed of a lobate cephalis, a thorax, and an abdomen.

The family Pylobotryida comprises those Botryodea in which the shell exhibits two parallel transverse annular constrictions, and is divided by these into three successive joints, corresponding to the cephalis, the thorax, and the abdomen of the Tricyrtida. As in the latter, the abdomen is here also a later production, arising from the terminal mouth of the thorax; therefore the Pylobotryida must be derived phylogenetically from the Lithobotryida.

Two genera of Pylobotryida were incompletely described in 1860 by Ehrenberg, Botryocyrtis and Botryocampe. We retain them here, with a stricter definition, however. Two other genera were added in my Prodromus—Pylobotrys and Phormobotrys. The small number of species here enumerated may be easily increased, since numerous forms, belonging probably to this family, are not sufficiently known. Their study is, however, very difficult and requires accurate examination of the tiny shells from different sides.

The four genera of Pylobotryida, here described, represent two different subfamilies. The terminal mouth of the abdomen remains open in the Botryocyrtida, whilst it becomes closed by a lattice-plate in the Botryocampida. There are in both groups shells with and without porous tubes; the number of these tubes, and also the number and disposition of the lobes in the cephalis, exhibits remarkable differences in the different species of those genera, and may in future serve for their division into a greater number of genera.

Synopsis of the Genera of Pylobotryida.

Genus 492. Botryocyrtis,^[109] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 829.

Definition.—Pylobotryida without tubes on the cephalis, and with the mouth of the abdomen open.

The genus Botryocyrtis, founded by Ehrenberg upon two Indian species, is the simplest among the Pylobotryida. It may have been derived from Botryopyle by the development of an abdomen (or a third shell-joint), the mouth of which remains open.

1. Botryocyrtis serpentis, Ehrenberg.

Cephalis quadrilobate; the odd frontal and the two paired buccal lobes subspherical, about half as large as the odd occipital lobe. Thorax inflated, about as long as the cephalis and half as long as the ovate abdomen. Mouth of the latter constricted, of half the breadth.

Dimensions.—Length of the shell 0.12, breadth 0.06.

Habitat.—Indian Ocean (Zanzibar), depth 2200 fathoms, Pullen.

2. Botryocyrtis theocampe, n. sp. (Pl. 96, fig. 19).

Cephalis quadrilobate; the odd frontal and the two paired buccal lobes hemispherical, about half as large as the helmet-shaped occipital lobe. Thorax cylindrical, of equal length and breadth, one and a half times as broad as the cephalis and as the cylindrical abdomen. Pores rather large, irregular, roundish.

Dimensions.—Length of the shell 0.12, breadth 0.06.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

3. Botryocyrtis cerebellum, n. sp. (Pl. 96, fig. 18).

Cephalis quinquelobate; the odd frontal and the two paired buccal lobes ovate, about half as large as the two helmet-shaped paired occipital lobes (?). Thorax campanulate, twice as broad and long as the cephalis and as the truncate cylindrical abdomen.

Dimensions.—Length of the shell 0.12, breadth 0.08.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

4. Botryocyrtis quinaria, Ehrenberg.

Cephalis quinquelobate; the odd occipital lobe ovate, twice as large as each of the other four subspherical lobes, the two anterior (or frontal) of which are somewhat smaller than the two posterior (or buccal). Thorax campanulate, somewhat larger than the truncate abdomen. Pores rather large, irregular.

Dimensions.—Length of the shell 0.09, breadth 0.05.

Habitat.—Indian Ocean (Zanzibar and Madagascar), surface.

Genus 493. Pylobotrys,^[110] Haeckel, 1881, Prodromus, p. 440.

Definition.—Pylobotryida with tubes on the cephalis, and with the mouth of the abdomen open.

The genus Pylobotrys differs from the closely allied Acrobotrys, its ancestral form, in the development of an abdomen or a third shell-joint, the basal mouth of which remains open.

1. Pylobotrys putealis, n. sp. (Pl. 96, fig. 21).

Cephalis multilobate, with a single curved and descending tube on the base of its anterior part (sternal tube). Occipital half of the cephalis divided into three large odd lobes (the largest the apical); facial half divided into three to five lobes, an odd frontal and one or two lateral pairs of small buccal lobes. Thorax truncate conical, about as large as the cephalis and larger than the truncate abdomen. Pores regular circular.

Dimensions.—Length of the shell 0.12, breadth 0.08.

Habitat.—Tropical Atlantic Station 347, depth 2250 fathoms.

2. Pylobotrys fontinalis, n. sp. (Pl. 96, fig. 20).

Cephalis trilobate, with three ovate lobes in the sagittal plane, of nearly equal size, and two divergent cylindrical tubes conical at the base. An ascending apical tube on the apex of the occipital lobe and a descending sternal tube on the base of the frontal lobe. The middle lobe between the former distinctly exhibits in the apical view (fig. 20) the collar septum with the four cortinar pores. Thorax campanulate, larger than the cephalis and the truncate abdomen.

Dimensions.—Length of the shell 0.11, breadth 0.06.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

3. Pylobotrys cerebralis, n. sp. (Pl. 96, fig. 22).

Cephalis multilobate, with four divergent cylindrical tubes, which are cylindrical, obliquely truncate at the mouth, and correspond in position to the four typical spines of Cortina; an ascending apical tube and three descending basal tubes (an odd caudal and two paired pectoral). The helmet-shaped occipital lobe is about as large as the frontal half of the cephalis, which is divided into three pairs of smaller pyriform lobes. Thorax subspherical, about as large as the cephalis and half as large as the inflated abdomen. Pores very scarce and small.

Dimensions.—Length of the shell 0.15, breadth 0.08.

Habitat.—Indian Ocean, Cocos Islands, Rabbe, surface.

Genus 494. Botryocampe,^[111] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 829.

Definition.—Pylobotryida without tubes on the cephalis, and with the mouth of the abdomen closed.

The genus Botryocampe may be derived from Botryocyrtis by development of a basal lattice-plate, closing the terminal mouth of the abdomen. It is at the same time closely allied to the Tricyrtid Theocapsa, and may be perhaps derived from this by lobation of the cephalis.

1. Botryocampe inflata, Ehrenberg.

Cephalis trilobate, inflated, of about the same breadth and length as the tun-shaped thorax and the hemispherical abdomen. Frontal lobes of the cephalis ovate, a little smaller than the ovate odd occipital lobe. Pores numerous and small.

Dimensions.—Length of the shell 0.05 to 0.08, breadth 0.02 to 0.04.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, Stations 267 to 274, 241, 354, &c., surface, and in various depths.

2. Botryocampe theocapsa, n. sp.

Cephalis trilobate, half as long as the campanulate thorax, and one-third as long as the ovate abdomen. Frontal lobes subspherical, scarcely half as long as the helmet-shaped occipital lobe. Pores very small and scarce.

Dimensions.—Length of the shell 0.12, breadth 0.04.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

3. Botryocampe galea, Haeckel.

Cephalis quinquelobate, about as large as the ovate thorax, and twice as large as the hemispherical abdomen (which is identical with the "crista obtusa finis anterioris" of Ehrenberg). Occipital lobe helmet-shaped, about twice as long as the two pairs of lateral lobes (the superior frontal and the inferior buccal lobes).

Dimensions.—Length of the shell 0.08, breadth 0.04.

Habitat.—Fossil in Barbados.

4. Botryocampe rotalia, n. sp. (Pl. 96, fig. 23).

Cephalis quinquelobate, half as large as the campanulate thorax and the subspherical abdomen. Occipital lobe ovate, one and a half times as long as the two ovate frontal lobes, and three times as long as the two subspherical buccal lobes. Collar septum with six distinct cortinar pores (two anterior jugular, two middle cardinal and two posterior cervical, fig. 23).

Dimensions.—Length of the shell 0.1, breadth 0.06.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

5. Botryocampe camerata, n. sp. (Pl. 96, fig. 24).

Cephalis multilobate, about as long and half as broad as the irregularly campanulate thorax, which is half as long as the subspherical large abdomen. Occipital lobe of the cephalis helmet-shaped, larger than its uviform frontal part, which is divided into six to eight small subspherical lobes. In the interior of the thorax and abdomen irregularly branched rods are visible, which divide their inner space into compartments or incomplete chambers. Pores large, regular, circular, hexagonally framed.

Dimensions.—Length of the shell 0.15, breadth 0.09.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Genus 495. Phormobotrys,^[112] Haeckel, 1881, Prodromus, p. 440.

Definition.—Pylobotryida with tubes on the cephalis, and with the mouth of the abdomen closed.

The genus Phormobotrys differs from the similar and closely allied Pylobotrys in the development of a basal lattice-plate closing the terminal mouth of the thorax, and corresponds therefore to Lithobotrys among the Lithobotryida. As in the latter and in Cannobotrys, &c., so here in Phormobotrys, different subgenera may be distinguished, according to the different number and disposition of the radial tubes which become developed from the lobate cephalis.

1. Phormobotrys trithalamia, n. sp. (Pl. 96, fig. 26).

Cephalis trilobate, with a single apical tube, which is only one-third as long, spindle-shaped, pointed, with frontal opening. Frontal lobes ovate, two-thirds as long as the helmet-shaped occipital lobe. Internal frontal septum of the cephalis with four large pores. Thorax cylindrical, twice as long as the hemispherical abdomen. Pores small and numerous, irregular, roundish.

Dimensions.—Length of the shell 0.16, breadth 0.05.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Phormobotrys pentathalamia, n. sp. (Pl. 96, fig. 27).

Cephalis quinquelobate, with a single conical apical tube of the same length, which has an obliquely truncate frontal opening. Odd frontal and paired buccal lobes smaller than the sternal and the occipital lobe. Internal frontal septum with six large pores. Thorax inflated, a little larger than the subspherical abdomen. Pores subregular, circular.

Dimensions.—Length of the shell 0.15, breadth 0.08.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

3. Phormobotrys hexathalamia, Haeckel.

Cephalis sexlobate, with a single apical horn, which is solid, vertical, cylindrical, pointed, only one-third as long. Frontal lobes subcylindrical, nearly as long as the kidney-shaped occipital lobe, three to four times as long as the small buccal lobes and the odd sternal lobe. Thorax tun-shaped, smaller than the cephalis, larger than the hemispherical abdomen. Pores numerous, subregular, circular.

Dimensions.—Length of the shell 0.13 to 0.15, breadth 0.05 to 0.06.

Habitat.—Mediterranean, Messina, surface.

4. Phormobotrys cannothalamia, n. sp. (Pl. 96, fig. 25).

Cephalis trilobate, of about the same breadth and length as the campanulate thorax, which is three times as long as the flat cap-shaped abdomen. The middle (or central) lobe of the cephalis is simple, nearly cubical, and smaller than the ovate occipital and frontal lobe. The two latter are prolonged into two slender cylindrical divergent tubes. Pores small and very numerous.

Dimensions.—Length of the shell 0.1, breadth 0.05.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

5. Phormobotrys polythalamia, n. sp.

Cephalis multilobate, of the same length and breadth as the subspherical thorax, and half as long as the ovate abdomen. Occipital lobe helmet-shaped, about as large as the frontal half of the cephalis, which is divided into six to eight lobes (two odd and two or three pairs of lateral lobes). Four cylindrical tubes corresponding to the four typical spines of Cortina, an ascending apical and three descending basal tubes (a posterior caudal and two anterior pectoral).

Dimensions.—Length of the shell 0.14, breadth 0.08.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

Suborder III. CYRTOIDEA, Haeckel, 1862.

Definition.—Nassellaria with a complete lattice-shell, exhibiting a simple or reduced cephalis, which is neither bilocular nor lobate, without sagittal constriction.

The order Cyrtoidea, described by me in 1862 as the family Cyrtida, is by far the largest of all the main groups of Radiolaria, and remarkable from the extraordinary variety of forms and the number of species. In the following system more than eleven hundred species are described, comprising about one-fourth of the number of species in the whole class of Radiolaria. This astonishing variety, however, is not effected by development of a large number of different types, but by an extraordinary variability within certain restricted boundaries, similar to what is seen among insects and birds. The number of genera, therefore, is comparatively small, and they may all be disposed into four families only, which in my Monograph (1862, p. 280) were distinguished as Monocyrtida, Dicyrtida, Tricyrtida and Stichocyrtida. If we divide these four groups in the following pages into twelve families and twenty-four subfamilies, we are guided by practical considerations only, hoping thereby to give a better survey of the difficult labyrinth of Cyrtoidean morphology.

The Cyrtoidea are characterised by this wonderful richness of specific forms not only in the present seas, but also for millions of years in the former ages of our globe. The majority of all the fossil Radiolaria which are now known belong to this group, and many species of it are so common that great rocks are formed by their union. The fact was first observed by Ehrenberg, who in his first system of Polycystina (1847, loc. cit., p. 54) enumerated forty-four genera and two hundred and eighty-two species; the Cyrtoidea, his Polycystina solitaria, form the preponderant majority of the whole class, viz., twenty-five genera and one hundred and ninety-three species.

In this first system (of 1847), as well as in the last systematic table of Ehrenberg (of 1875, loc. cit.), the Cyrtida as "Polycystina solitaria" are opposed to all other Radiolaria, as "Polycystina composita." The former bear the definition "Testæ siliceæ spatio interno ample pervio, aut passim levius transverse constricto"; the latter, however, "Testæ siliceæ spatio interno celluloso aut strictura longitudinali constricto." In reality these definitions are insufficient, and the conclusions which Ehrenberg derived from the organisation of the Polycystina solitaria and composita, were quite erroneous. So also are the definitions of the three families into which he divided the Polycystina solitaria, afterwards (in 1875) called by him "Monodictya nassellaria." These three families were the Halicalyptrina, Lithochytrina and Eucyrtidina. With these were also united the three genera of Botryodea known to Ehrenberg (Lithobotrys, Botryocampe, Botryocyrtis). We entirely separate these here from the true Cyrtida, on account of their lobate or multilocular cephalis.

Whilst Ehrenberg only knew the skeleton of the Polycystina solitaria, the first observations of living Cyrtida were published by Johannes Müller, 1858, in his fundamental treatise. He gave the first description and figures of the central capsule of this group, with the characteristic lobes developed from its basal part; and of the pseudopodia radiating on all sides (loc. cit., Taf. vi.). The forms described by him were all Mediterranean, one Dicyrtid (Lithomelissa mediterranea), two Tricyrtids (Eucyrtidium zancleum and Pterocanium charybdeum), and one Stichocyrtid (Lithocampe tropeziana).

In my monograph (1862, p. 272-341) I gave a detailed description of all known and some new Cyrtida, and characterised this family by the fundamental monaxonial form of the shell, with two different poles (an upper apical and a lower basal pole), and by the unipolar growth, beginning from the apical pole. I pointed out also the peculiar structure of the monaxonial central capsule. At that time I divided the Cyrtida into five subfamilies, in which, however, the Spyroidea (= Zygocyrtida), and the Botryodea (= Polycyrtida) were united with the true Cyrtoidea (Monocyrtida, Dicyrtida, Stichocyrtida).

The astonishing number of new and interesting forms of Cyrtida which I found in the rich collection of the Challenger (beginning from 1876), and mainly in the Radiolarian ooze of the Central Pacific (Stations 263 to 274), enabled me to give in my Prodromus, in 1881, a greatly enlarged and amended system of this important group. I separated there the Spyroidea (= Zygocyrtida), and the Botryodea (= Polycyrtida) from the true Cyrtoidea by restricted definition, pointing out the essential differences in the structure of the cephalis in these groups of Cyrtellaria. The latter name, as here used, is therefore identical with the "Cyrtida" of my Monograph. In the Prodromus I divided the true Cyrtida (p. 426) into five subfamilies and thirty tribes, corresponding to the differences in the number of the shell-joints and of the radial apophyses, and in the shape of the closed or open mouth. These groups are here retained, but reduced to four families and twenty-four subfamilies, since the Tetracyrtida are better united with the Stichocyrtida (compare below).

Richard Hertwig in his work Organismus der Radiolarien (1879, pp. 74 to 86) gave the first accurate description of the finer structure of the central capsule of the Cyrtida, and pointed out their character as true Monopylea, with porochora and podoconus, and the peculiar shape of its nucleus. He also published excellent figures of some interesting new species.

O. Bütschli, 1882, in his valuable paper entitled: "Beiträge zur Kentniss der Radiolarien-Skelette, insbesondere der der Cyrtida" (Zeitschr. für wiss. Zool., vol. xxxvi. p. 485) made an attempt at a natural classification of the Cyrtida, which he derived from the Spyroidea or Zygocyrtida. As already mentioned above, we cannot accept this essay as the foundation of a true natural system, since the affinities of the Cyrtellaria (and of the Nassellaria as a whole) are far more complicated and difficult than Bütschli supposed. His views were supported by accurate observations only on the structure of the fossil Cyrtoidea of Barbados; these, however, represent the minority only of the genera, and many interesting and important forms (mainly of true "Monocyrtida") remained unknown to Bütschli. A great part, however, of his observations are very useful, and his remarks on comparative morphology are very suggestive.

The Cyrtoidea may be divided into families and subfamilies according to three different principles, viz., (1) the number of joints into which the shell is divided by transverse strictures; (2) the number of radial apophyses which arise from the shell; (3) the shape of the basal mouth, which is either open or closed by a lattice-plate. At present every attempt of classification in this large group must be more or less artificial, since the affinities of the numerous smaller and larger groups are extremely complicated, and the ontogeny, the only sure guide in this phylogenetical labyrinth, is perfectly unknown. It seems therefore the most convenient to employ for our artificial classification, first, the number of shell-joints, second, the radial structure, and third, the shape of the mouth.

A. The number of joints into which the shell is divided by transverse constrictions, serves here for the distinction of four primary groups or suborders of the Cyrtoidea, viz., (1) Monocyrtida with one joint; (2) Dicyrtida with two joints; (3) Tricyrtida with three joints; and (4) Stichocyrtida with four or more joints. In my Prodromus (1881, p. 426) I divided the latter group into Tetracyrtida (with four joints), and Stichocyrtida (with five or more joints); but these two groups may be united, since the fourth and all the succeeding joints are of rather indifferent shape and of little morphological value. The three first joints, however, are usually very different and possess a high morphological importance, so that we distinguish the first joint as cephalis, the second as thorax, and the third as abdomen. The uppermost transverse constriction, which separates the two first joints, cephalis and thorax, is the collar stricture and is usually caused by an internal fenestrated septum, the cortinar septum. The second constriction, which separates the second and third joints (thorax and abdomen) is called the lumbar constriction. The following constrictions (in the Stichocyrtida) are indifferent and of little morphological interest, and require therefore no peculiar designation.