Chapter XXIII: Section III: TRICYRTIDA, Haeckel, 1881, Prodromus, p. 426, 434 (4)

Shell dome-shaped, with slight collar and deep lumbar stricture. Length of the three joints = 1 : 6 : 5, breadth = 1 : 7 : 8. Cephalis small, with a conical horn of the same length. Thorax cupola-shaped, with large, regular, circular pores, and numerous pyramidal tubercles. Abdomen with twelve (sometimes eleven or thirteen) slender, divergent ribs, which are connected at equal distances by four to six horizontal rings, and so produce twelve longitudinal rows of large, regular, square meshes.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.12, _c_ 0.1; breadth, _a_ 0.03, _b_ 0.14, _c_ 0.15.

_Habitat._--Central Pacific, Stations 263 to 274, depth 2350 to 2925 fathoms.

10. _Cycladophora dodecapleura_, n. sp.

Shell cupola-shaped, with two deep strictures. Length of the three joints = 2 : 5 : 6, breadth = 2 : 7 : 10. Cephalis hemispherical, with a conical horn of twice the length. Thorax subspherical, truncate at both poles, thorny, with regular, circular pores. Abdomen in the upper half with a coronal of twelve large ovate holes, separated by twelve divergent, slender ribs, in the lower half with curved, convergent prolongations of the twelve ribs, and numerous small, irregular, roundish pores.

_Dimensions._--Length of the three joints, _a_ 0.015, _b_ 0.05, _c_ 0.06; breadth, _a_ 0.02, _b_ 0.07, _c_ 0.1.

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

11. _Cycladophora campanula_, n. sp.

Shell campanulate, with two slight strictures. Length of the three joints = 2 : 4 : 5, breadth = 2 : 6 : 10. Cephalis ovate, with a conical horn of the same length. Thorax campanulate, rough, with regular, circular pores. Abdomen dilated, with fifteen to twenty slender, divergent, little curved ribs, which are connected by two or three horizontal rings, and from two or three transverse rows of large, roundish, square pores.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.08, _c_ 0.1; breadth, _a_ 0.04, _b_ 0.12, _c_ 0.2.

_Habitat._--North Atlantic, Bermuda, surface; also fossil in Barbados.

12. _Cycladophora spatiosa_, Ehrenberg.

_Cycladophora spatiosa_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 68, Taf. xviii. figs. 5, 6.

Shell campanulate, with two slight strictures. Length of the three joints = 2 : 6 : 9, breadth = 3 : 8 : 14. Cephalis subspherical, with a conical horn of the same length. Thorax campanulate, {1380}smooth, with regular, circular pores. Abdomen truncate, conical, with sixteen to twenty-four divergent ribs, which are straight or slightly curved, and connected by from four to six transverse, circular rings. The large regular meshes, so produced, form sixteen to twenty-four longitudinal series, and are rounded in the upper, square in the lower transverse rows.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.06, _c_ 0.09; breadth, _a_ 0.03, _b_ 0.08, _c_ 0.14.

_Habitat._--Fossil in Barbados.

13. _Cycladophora favosa_, n. sp. (Pl. 62, figs. 5, 6).

Shell dome-shaped, without collar stricture, but with a deep lumbar stricture. Cephalis flat, cap-shaped, without horn, or with a rudimentary conical horn, with small circular pores. Length of the three joints = 1 : 4 : 3, breadth = 2 : 5 : 4. Thorax subspherical, rough, with regular, circular, hexagonally-framed pores. Abdomen truncate, conical, with eighteen to twenty-four prominent ribs; between every two ribs only two or three ovate pores occur. Mouth circular, with eighteen to twenty-four teeth. The shape of the abdomen is rather variable (figs. 5, 6).

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.08, _c_ 0.06; breadth, _a_ 0.04, _b_ 0.09, _c_ 0.07.

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

Subgenus 5. _Cyclamptidium_, Haeckel.

_Definition._--Abdomen nearly cylindrical or prismatic, with numerous (ten to twenty or more) straight, vertical, parallel ribs. Mouth wide open, truncate.

14. _Cycladophora fenestrata_, n. sp. (Pl. 68, fig. 2).

Shell rough, with two slight strictures. Length of the three joints = 1 : 5 : 5, breadth = 1 : 6 : 5. Cephalis conical, with a conical, dimpled horn of twice the length. Thorax nearly spherical, with regular, circular pores, and small conical spines. Abdomen cylindrical, with eighteen stout, parallel, vertical ribs, which are connected by six to eight horizontal, circular rings; therefore regular transverse and longitudinal rows of square or circular pores occur. Mouth truncate, circular.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.1, _c_ 0.1; breadth, _a_ 0.03, _b_ 0.12, _c_ 0.1.

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

15. _Cycladophora stiligera_, Ehrenberg.

_Cycladophora stiligera_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 68, Taf. xviii. fig. 3.

Shell smooth, with two distinct strictures. Length of the three joints = 2 : 7 : 8, breadth = 2 : 9 : 7. Cephalis subspherical, with a conical horn of twice the length. Thorax subspherical, smooth, with regular, circular pores. Abdomen cylindrical, with twelve parallel, vertical ribs, which {1381}are connected by three to four broad, horizontal rings; therefore subregular, transverse, and longitudinal rows of roundish pores are present. Mouth truncate, circular.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.07, _c_ 0.08; breadth, _a_ 0.02, _b_ 0.09, _c_ 0.07.

_Habitat._--Fossil in Barbados.

Genus 605. _Calocyclas_,[222] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

_Definition._--#Theophormida# (vel Tricyrtida multiradiata aperta) with a simple corona of terminal feet around the truncate mouth. Abdomen not dilated, cylindrical or ovate. No ribs in the shell-wall.

The genus _Calocyclas_, and the three following closely allied genera, differ from the four preceding genera of Theophormida in the absence of radial or longitudinal ribs in the wall of the thorax and abdomen. These are completely reduced, and their terminal prolongations only remain, forming a simple or double corona around the mouth of the abdomen. They correspond therefore to _Carpocanium_ and _Anthocyrtis_ among the Dicyrtida. In _Calocyclas_ the corona is simple. The mouth is not dilated, but often constricted, and the abdomen is cylindrical or ovate, not conical. The teeth of the corona are usually vertical or convergent.

Subgenus 1. _Calocycletta_, Haeckel.

_Definition._--Thorax and abdomen smooth, without spines or thorns.

1. _Calocyclas veneris_, n. sp. (Pl. 74, fig. 5).

Shell smooth, with two distinct strictures. Length of the three joints = 1 : 2 : 2, breadth = 1 : 4 : 3. Cephalis ovate, with a large, triangular, prismatic horn of three times the length. Thorax hemispherical; abdomen cylindrical; both with regular, circular pores of equal size. Mouth truncate, with a corona of nine to twelve vertical, lamellar feet, which are as long as the abdomen, rectangular, twice as broad as their distance apart, and truncate at the end.

_Dimensions._--Length of the three joints, _a_ 0.03 to 0.04, _b_ 0.06 to 0.08, _c_ 0.04 to 0.06; breadth, _a_ 0.03 to 0.04, _b_ 0.09 to 0.11, _c_ 0.08 to 0.1.

_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, many stations; surface, and in various depths.

2. _Calocyclas virginis_, n. sp. (Pl. 74, fig. 4).

Shell smooth, with distinct collar, but indistinct lumbar stricture. Length of the three joints = 1 : 2 : 1, breadth = 1 : 4 : 3. Cephalis ovate, with a slender, conical horn, little shorter than the {1382}shell. Thorax subspherical. Abdomen nearly cylindrical, little contracted towards the peristome. Pores regular, circular, twice as broad in the thorax as in the abdomen, where they are separated by slight longitudinal ribs. Corona of the peristome composed of sixteen to twenty-four vertical, lamellar feet, which are longer than the abdomen, rectangular, and truncate at the end.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.08, _c_ 0.05; breadth, _a_ 0.03, _b_ 0.11, _c_ 0.09.

_Habitat._--Central Pacific, Station 225, depth 4475 fathoms.

3. _Calocyclas minervæ_, n. sp.

Shell smooth, with two deep strictures, similar to _Cycladophora stiligera_. Length of the three joints = 1 : 4 : 3, breadth = 1 : 4 : 3. Cephalis subspherical, with a large, conical horn of three times the length. Thorax subspherical, with small, regular, circular pores. Abdomen cylindrical, with truncate mouth and few irregular pores of different sizes, commonly arranged in three or four subregular, transverse rows, with large intervening distances. Peristome with a corona of twelve to twenty vertical, lamellar feet, which are about as long as the abdomen, and truncate at the end (in Ehrenberg's figure these are broken off).

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.08, _c_ 0.06; breadth, _a_ 0.02, _b_ 0.09, _c_ 0.07.

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

4. _Calocyclas amicæ_, n. sp. (Pl. 74, fig. 2).

Shell smooth, with two slight strictures. Length of the three joints = 2 : 4 : 5, breadth = 2 : 5 : 5. Cephalis subspherical, with a pyramidal horn of the same length. Thorax campanulate-conical; abdomen nearly cylindrical; both with small, subregular, circular pores. Peristome with a corona of twelve to fifteen small, triangular feet, only as large as the thickness of the shell-wall, and separated by distances of twice the size.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.08, _c_ 0.1; breadth, _a_ 0.04, _b_ 0.1, _c_ 0.1.

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

5. _Calocyclas sacerdotis_, n. sp.

Shell smooth, with two deep strictures. Length of the three joints = 1 : 3 : 4, breadth = 1 : 3 : 3. Cephalis ovate, with a pyramidal horn of three times the length. Thorax campanulate, conical; abdomen twice the length, cylindrical; both with small, regular, circular pores. Peristome somewhat constricted, with a corona of nine to twelve conical feet, which are as long as the cephalis, and with the ends curved inwards, protecting the mouth.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.08, _c_ 0.12; breadth, _a_ 0.03, _b_ 0.09, _c_ 0.09.

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

6. _Calocyclas vestalis_, n. sp. (Pl. 74, fig. 3).

Shell smooth, with two deep strictures. Length of the three joints = 1 : 2 : 3, breadth = 1 : 3 : 3. Cephalis subspherical, with a pyramidal horn of twice the length. Thorax campanulate; abdomen {1383}nearly cylindrical; both with regular, hexagonal pores, three times as broad as the bars. Peristome constricted, half as broad as the abdomen, with a corona of nine conical, vertical feet as long as the cephalis.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.07, _c_ 0.1; breadth, _a_ 0.035, _b_ 0.1, _c_ 0.1.

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

Subgenus 2. _Calocyclissa_, Haeckel.

_Definition._--Thorax spiny or thorny; abdomen smooth.

7. _Calocyclas turris_, Ehrenberg.

_Calocyclas turris_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 66, Taf. xviii. fig. 7.

Shell with two sharp strictures. Length of the three joints = 1 : 4 : 4, breadth = 1 : 5 : 4. Cephalis hemispherical, with a stout conical horn of the same length. Thorax subspherical, thorny with small, regular, circular, quincuncial pores. Abdomen cylindrical, smooth, nearly hyaline, with very scarce, irregular, widely scattered pores. Peristome with a corona of fifteen to twenty broad, lamellar, vertical, truncate feet, about as long as the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.08, _c_ 0.08; breadth, _a_ 0.03, _b_ 0.1, _c_ 0.08.

_Habitat._--Fossil in Barbados.

8. _Calocyclas hyalogaster_, n. sp.

Shell with two sharp strictures. Length of the three joints = 1 : 4 : 6, breadth = 1 : 4 : 3. Cephalis subspherical, with a conical horn of twice the length. Thorax subspherical, thorny, with regular, circular pores. Abdomen cylindrical, smooth, quite hyaline, without any pores. Peristome with a corona of twelve broad, lamellar, vertical, truncate feet, half as long as the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.08, _c_ 0.12; breadth, _a_ 0.02, _b_ 0.08, _c_ 0.06.

_Habitat._--South Pacific, Station 300, depth 1375 fathoms.

9. _Calocyclas erinaceus_, Haeckel.

_Cycladophora erinaceus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. xviii. fig. 2.

Shell with two sharp strictures. Length of the three joints = 2 : 9 : 5, breadth = 3 : 9 : 5. Cephalis subspherical, rough, with a short and broad conical horn of half the length. Thorax ovate, densely covered with conical spines as long as the horn, and with regular, circular, quincuncial pores. Abdomen cylindrical, smooth, with irregular roundish pores of different sizes. Peristome with twelve to fifteen vertical, broad, lamellar, truncate feet half as long as the abdomen (in Ehrenberg's figure these are broken off).

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.18, _c_ 0.1; breadth, _a_ 0.06, _b_ 0.18, _c_ 0.1.

_Habitat._--Fossil in Barbados.

{1384}10. _Calocyclas gigas_, Haeckel.

_Cycladophora gigas_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 68, Taf. xviii. fig. 1.

Shell with two sharp strictures. Length of the three joints = 2 : 5 : 3, breadth = 2 : 6 : 4. Cephalis subspherical, rough, with a short and broad conical horn of half the length. Thorax subspherical, campanulate, thorny, with subregular, circular pores (smaller and more numerous than in the preceding). Abdomen cylindrical, smooth, with a small number of sparsely disposed, roundish, irregularly scattered pores. Peristome with twenty to thirty short, lamellar, truncate, vertical feet about half as long as the cephalis.

_Dimensions._--Length of the three joints, _a_ 0.06, _b_ 0.15, _c_ 0.09; breadth, _a_ 0.06, _b_ 0.18, _c_ 0.12.

_Habitat._--Fossil in Barbados.

Subgenus 3. _Calocycloma_, Haeckel.

_Definition._--Thorax smooth; abdomen spiny or thorny.

11. _Calocyclas casta_, n. sp. (Pl. 73, fig. 10).

Shell ovate, with two sharp strictures. Length of the three joints = 1 : 2 : 8, breadth = 2 : 4 : 8. Cephalis hemispherical, with a strong pyramidal horn of twice the length. Thorax campanulate, smooth, with small, regular, circular pores. Abdomen inflated, subspherical, covered with large conical spines, and large intervening circular pores (four times as broad as the thoracic pores). Mouth constricted, only one-third as broad as the abdomen, with a peristome of nine to twelve conical vertical feet as long as the abdominal spines. (In the specimen figured they were broken off.)

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.04, _c_ 0.15; breadth, _a_ 0.04, _b_ 0.08, _c_ 0.15.

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

12. _Calocyclas pudica_, n. sp.

Shell ovate, with two distinct strictures. Length of the three joints = 1 : 3 : 8, breadth = 1 : 4 : 6. Cephalis subspherical, with a conical horn of three times the length. Thorax and abdomen nearly of the same shape as in the preceding species, but more slender and the regular, circular pores of the abdomen only twice as broad as the thoracic pores. Conical spines of the abdomen only half as large, but more numerous. Peristome constricted, half as broad as the abdomen, with sixteen to twenty short, conical, vertical feet as long as the cephalis.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.06, _c_ 0.16; breadth, _a_ 0.025, _b_ 0.08, _c_ 0.12.

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

Subgenus 4. _Calocyclura_, Haeckel.

_Definition._--Thorax and abdomen spiny or thorny.

{1385}13. _Calocyclas parthenia_, n. sp. (Pl. 74, fig. 1).

Shell nearly ovate, with thorny surface, and two slight strictures. Length of the three joints = 1 : 2 : 4, breadth = 2 : 4 : 5. Cephalis hemispherical, armed with numerous short, conical thorns, and with a pyramidal, very large, vertical horn as long as the thorax, and on the basal half as broad as the cephalis. Thorax hemispherical, separated by a slight stricture from the broader, barrel-shaped abdomen, which is a little constricted at the mouth. Teeth of the coronal about twenty, triangular, short, little divergent. Pores circular, somewhat irregular in size, three to four times as broad as the bars, in all three joints nearly of the same shape.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.11; breadth, _a_ 0.05, _b_ 0.1, _c_ 0.12.

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

14. _Calocyclas aspasia_, n. sp.

Shell ovate, conical, with two deep strictures. Length of the three joints = 1 : 3 : 4, breadth = 1 : 4 : 5. Cephalis subspherical, with a conical horn of twice the length. Thorax and abdomen nearly of the same shape as in the preceding species, but covered with longer conical spines, less numerous, and twice as long as the diameter of the subregular, circular pores. Mouth more constricted, and armed with a coronal of twelve to sixteen broad, lamellar feet, as long as the cephalis, and similar to those of _Calocyclas puella_ (Pl. 74, fig. 5).

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.06, _c_ 0.08; breadth, _a_ 0.03, _b_ 0.08, _c_ 0.1.

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

15. _Calocyclas monumentum_, n. sp. (Pl. 73, fig. 9).

Shell nearly conical, with two very deep strictures, everywhere covered with long, bristle-shaped, divergent spines, about as long as the thorax. Length of the three joints = 1 : 2 : 2, breadth = 1 : 4 : 6. Cephalis nearly spherical, with a very large, three-sided pyramidal horn of twice the length. Thorax and abdomen of similar form, campanulate, with a lower cylindrical, and an upper truncate, conical part. Pores irregular, roundish, in the smaller thorax of slightly different sizes, in the larger abdomen three to four transverse rows of larger pores (six to eight in each row) are separated by numerous much smaller pores. Peristome wide open, with a coronal of twelve large, triangular, vertical feet, nearly as long as the abdomen; in the base of each foot a large, roundish, triangular pore.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.06; breadth, _a_ 0.04, _b_ 0.12, _c_ 0.18.

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

Genus 606. _Clathrocyclas_,[223] Haeckel, 1881, Prodromus, p. 434.

_Definition._--#Theophormida# (vel Tricyrtida multiradiata aperta) with a simple corona of terminal feet around the dilated mouth. Abdomen dilated, truncate-conical, or discoidal. No ribs in the shell-wall.

{1386}The genus _Clathrocyclas_ differs from the preceding closely allied _Calocyclas_ in the dilated mouth and the flatter form of the abdomen, which is usually truncate, conical, or nearly discoidal. The conical thorax is often separated from the flat abdomen by an elegant ribbon of small quadrangular pores. The feet or teeth of the terminal corona are divergent, or even horizontally expanded, whilst in _Calocyclas_ they are usually vertical or somewhat convergent.

Subgenus 1. _Clathrocyclia_, Haeckel.

_Definition._--Shell highly conical, often ovate or slenderly campanulate. Cephalis commonly with a single horn.

1. _Clathrocyclas principessa_, n. sp. (Pl. 74, fig. 7).

Shell ovate, with two distinct strictures. Length of the three joints = 1 : 2 : 1, breadth = 1 : 2 : 2. Cephalis hemispherical, large, with a pyramidal, occipital horn of the same length. Thorax subspherical, with irregular, circular pores, about as broad as the bars. Abdomen short, widely open with a single transverse row of circular pores, and a coronal of twelve triangular, divergent feet, as long as the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.03; breadth, _a_ 0.04, _b_ 0.08, _c_ 0.09.

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

2. _Clathrocyclas basilea_, (Pl. 74, fig. 6).

Shell campanulate, with two deep strictures. Length of the three joints = 2 : 5 : 3, breadth = 3 : 7 : 9. Cephalis hemispherical, with an ovate, oblique horn of the same length. Thorax hemispherical, with subregular, circular pores of the same breadth as the bars. Abdomen short, with two transverse rows of the same pores, and with a coronal of sixteen to twenty ovate, divergent feet, as long as the horn.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.03; breadth, _a_ 0.035, _b_ 0.07, _c_ 0.09.

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

3. _Clathrocyclas fimbriata_, Haeckel.

? _Halicalyptra fimbriata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 72, Taf. ii. fig. 11.

Shell campanulate, with two deep strictures. Length of the three joints = 1 : 3 : 1, breadth = 1 : 3 : 5. Cephalis hemispherical, with a conical horn of twice the length. Thorax hemispherical, in the upper half hyaline, without pores, in the lower half with four to six transverse rows of subregular, circular pores. Abdomen short, suddenly dilated, with one or two transverse rows of larger {1387}ovate pores (six to eight in one row), and with a coronal of twelve to fifteen divergent, slender, curved feet, as long as the cephalis. (In the figure of Ehrenberg, seen half from below, the cephalis is not represented.)

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.06, _c_ 0.02; breadth, _a_ 0.02, _b_ 0.06, _c_ 0.1.

_Habitat._--Fossil in Barbados.

4. _Clathrocyclas collaris_, n. sp. (Pl. 74, fig. 8).

Shell subconical, with two indistinct strictures. Length of the three joints = 1 : 1 : 2, breadth = 1 : 2 : 3. Cephalis hemispherical, with a triangular prismatic horn three times the length. Thorax truncate, conical, with a single transverse row of circular pores, each of which is placed in the lower end of an oblong, lanceolate, longitudinal furrow; collar composed of fifteen to twenty such furrows. Abdomen inflated, with four to six transverse rows of circular pores, and with a coronal of nine triangular, divergent feet, longer than the collar.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.03, _c_ 0.06; breadth, _a_ 0.03, _b_ 0.06, _c_ 0.09.

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

5. _Clathrocyclas puella_, Haeckel.

_Podocyrtis puella sinensis_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 82, Taf. xiv. fig. 3.

Shell subconical, with two indistinct strictures. Length of the three joints = 1 : 1 : 2, breadth = 1 : 2 : 3. Cephalis hemispherical, with a pyramidal horn of twice the length. Pores subregular, circular, quincuncial, in the dilated abdomen (with four to five transverse rows), twice to three times as large as in the short thorax (with two to three rows). Coronal of the wide peristome with fifteen to twenty short, triangular, divergent feet, about as long as the cephalis.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.02, _c_ 0.04; breadth, _a_ 0.02, _b_ 0.04, _c_ 0.06.

_Habitat._--Fossil in Barbados.

6. _Clathrocyclas domina_, Haeckel.

_Podocyrtis domina sinensis_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 82, Taf. xiv. fig. 4.

Shell subconical, with two slight strictures. Length of the three joints = 1 : 2 : 4, breadth = 1 : 3 : 4. Cephalis ovate, with a conical horn of the same length (and sometimes with some little accessory thorns at its base). Pores subregular, circular, quincuncial, in the dilated abdomen (with six to eight transverse rows), twice to four times as large as in the hemispherical thorax (with four to six rows). Coronal of the wide peristome with nine to twelve short, triangular, divergent feet, half as long as the cephalis (in Ehrenberg's figure incomplete).

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.04, _c_ 0.08; breadth, _a_ 0.02, _b_ 0.06, _c_ 0.08.

_Habitat._--Central Pacific, Stations 263 to 268, depth 2650 to 3000 fathoms; also fossil in Barbados.

{1388}Subgenus 2. _Clathrocycloma_, Haeckel.

_Definition._--Shell flatly conical, often widely campanulate, or nearly discoidal. Cephalis commonly with two or more horns.

7. _Clathrocyclas alcmenæ_, n. sp. (Pl. 59, fig. 6).

Shell conical, with two indistinct strictures. Length of the three joints = 2 : 10 : 1, breadth = 2 : 12 : 14. Cephalis hemispherical, with two divergent, pyramidal horns; frontal horn as long as the cephalis, occipital horn of twice the length. Thorax conical, with large hexagonal meshes, increasing gradually in size towards the short abdomen, which is represented only by a single circular girdle of small, square, abdominal pores. Coronal of the peristome with twenty to thirty triangular, divergent, nearly horizontal feet, as long as the cephalis.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.1, _c_ 0.01. _breadth_, _a_ 0.02, _b_ 0.12, _c_ 0.14.

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

8. _Clathrocyclas europæ_, n. sp. (Pl. 59, figs. 11, 12).

Shell conical, almost of the same form as the preceding nearly allied species, differing from it in the concave (not straight) outline of the flatter conical thorax, in the more rounded form of its pores, and in the subspherical form of the cephalis, bearing only a single conical horn of the same length. Length of the three joints = 2 : 8 : 1, breadth = 2 : 12 : 14. In fig. 11 the cephalis is broken off, so that the four cortinar pores are visible (two smaller jugular and two larger cardinal pores, separated by two coracal beams).

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.08, _c_ 0.01. _breadth_, _a_ 0.02, _b_ 0.12, _c_ 0.14.

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

9. _Clathrocyclas semeles_, n. sp. (Pl. 58, fig. 5).

Shell conical-campanulate, with two distinct strictures. Length of the three joints = 2 : 8 : 1, breadth = 2 : 8 : 10. Cephalis hemispherical, with three divergent, conical horns (the caudal horn, directed downwards, much longer than the occipital and frontal horns). Pores of the thorax large, roundish. Abdomen (as in the two preceding species) with only a single circle of forty to fifty small square pores. Coronal with about the same number of short, triangular, almost horizontally divergent feet.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.08, _c_ 0.01. _breadth_, _a_ 0.02, _b_ 0.08, _c_ 0.1.

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

10. _Clathrocyclas danaës_, n. sp. (Pl. 59, figs. 13, 14).

Shell flatly conical, with straight outline (as in _Clathrocyclas alcmenæ_, Pl. 59, fig. 6). Length of the three joints = 1 : 5 : 1, breadth = 2 : 8 : 1. Cephalis hemispherical, with a single, short, conical, {1389}oblique horn (broken off in the specimen figured). Pores of the thorax polygonal, increasing gradually in size towards the girdle (in three to four circles.) Abdomen nearly horizontally expanded with two rows of pores, the inner with very small and numerous square pores, the outer with twenty to thirty much larger quadrangular pores. Coronal of the peristome with the same number of short, divergent feet, alternating with the larger pores.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.1, _c_ 0.02; breadth, _a_ 0.04, _b_ 0.15, _c_ 0.2.

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

11. _Clathrocyclas jonis_, n. sp. (Pl. 59, fig. 9).

Shell campanulate, with two slight strictures. Length of the three joints = 1 : 5 : 2, breadth = 1 : 6 : 8. Cephalis small, hemispherical, with two divergent, conical horns of nearly equal length. Pores of the thorax polygonal, increasing in size towards the girdle; in the upper half filled up by an extremely fine and delicate cobweb-like network. Abdomen with two rows of pores, of the same shape as in the preceding species, also with equal coronal.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.1, _c_ 0.03; breadth, _a_ 0.02, _b_ 0.12, _c_ 0.16.

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

12. _Clathrocyclas latonæ_, n. sp. (Pl. 59, fig. 7).

Shell campanulate, very similar to the preceding species, but flatter and different in the larger cephalis, bearing only a single oblique horn. All the polygonal pores of the thorax are filled out by delicate cobweb-like network. Length of the three joints = 1 : 3 : 1, breadth = 1 : 4 : 6. Abdomen with three circular rows of quadrangular pores; first very small and numerous, second of median size, third very large. Coronal with thirty to forty short triangular feet.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.08, _c_ 0.03; breadth, _a_ 0.03, b 0.12, c 0.18.

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

13. _Clathrocyclas coscinodiscus_, n. sp. (Pl. 58, figs. 3, 4).

Shell flatly campanulate, with two distinct strictures. Length of the three joints = 1 : 5 : 2, breadth = 1 : 8 : 10. Cephalis hemispherical, with two divergent, pyramidal horns of the same length. Thorax with concave outline, with numerous hexagonal pores, gradually increasing in size towards the girdle, except the outermost row (inside the girdle), which is composed of very small, square pores. Abdomen (outside the girdle) with three rows of pores; first with small, second with median, third with large pores. Coronal with eighty to one hundred short, divergent feet.

_Dimensions._--Length of the three joints, _a_ 0.02, b 0.1, _c_ 0.03; breadth, _a_ 0.025, b 0.16, c 0.2.

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

{1390}14. _Clathrocyclas cassiopeiæ_, n. sp. (Pl. 59, fig. 5).

Shell flatly campanulate, with two slight strictures. Length of the three joints = 2 : 4 : 3, breadth = 2 : 6 : 8. Cephalis ovate, thorny, with a pyramidal horn of the same length, and several smaller accessory horns. Thorax smooth, with irregular, polygonal pores of nearly equal size. Abdomen spiny, with three to four irregular rows of similar pores. Coronal with sixty to ninety or more irregularly and obliquely divergent feet, little larger than the abdominal spines.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.08, _c_ 0.06; breadth, _a_ 0.03, _b_ 0.12, _c_ 0.16.

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

Genus 607. _Lamprocyclas_,[224] Haeckel, 1881, Prodromus, p. 434.

_Definition._--#Theophormida# (vel Tricyrtida multiradiata aperta) with a double corona of solid terminal feet around the mouth. No ribs in the shell-wall.

The genus _Lamprocyclas_ differs from _Calocyclas_, its ancestral form, in the duplication of the terminal corona. Usually the feet or teeth of the lower corona are convergent and curved inwards, whilst the teeth of the upper corona are divergent and curved outwards. Sometimes above the latter a third corona begins to be developed. The whole shell is more or less conical, very thick-walled, with a large and stout apical horn.

Subgenus 1. _Lamprocyclia_, Haeckel.

_Definition._--Feet of the peristome simple, not branched.

1. _Lamprocyclas nuptialis_, n. sp. (Pl. 74, fig. 15).

Shell campanulate, nearly smooth, with two slight strictures. Length of the three joints = 1 : 2 : 2, breadth = 1 : 3 : 4. Cephalis ovate, with a very large, three-sided prismatic horn, nearly as long as the shell. Thorax and abdomen gradually dilated, with regular, circular, double-edged pores. Outer coronal of the peristome with twelve to fifteen divergent feet, inner with as many subvertical, triangular, little curved feet, about as long as the cephalis.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.06; breadth, _a_ 0.03, _b_ 0.09, _c_ 0.12.

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

2. _Lamprocyclas maritalis_, n. sp. (Pl. 74, figs. 13, 14).

Shell campanulate, very similar to the preceding species in form and fenestration, but not so slender and with different peristome. Length of the three joints = 4 : 5 : 6, breadth = 4 : 10 : 13. Cephalis subspherical, with a very stout, pyramidal horn of twice the length, the edges of which are {1391}spirally convoluted. Outer coronal of the peristome with twelve to fifteen short, divergent feet, inner with as many convergent, longer feet.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.05, _c_ 0.06; breadth, _a_ 0.04, _b_ 0.1, _c_ 0.13.

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

3. _Lamprocyclas deflorata_, n. sp. (Pl. 74, fig. 10).

Shell ovate, smooth, with deep collar, but indistinct lumbar stricture; very similar to the two preceding species, but with different horn and peristome. Length of the three joints = 3 : 5 : 8, breadth = 3 : 10 : 13. Cephalis subspherical, with a pyramidal horn of twice the length, the three faces of which are deeply concave. Thoracic pores half as large as the abdominal, both subregular, double-edged. Outer coronal of the wide peristome with nine short, triangular, subvertical feet, inner with nine larger, horizontal feet, lying in the plane of the wide mouth.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.05, _c_ 0.08; breadth, _a_ 0.03, _b_ 0.1, _c_ 0.13.

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

4. _Lamprocyclas saltatricis_, n. sp. (Pl. 74, fig. 16).

Shell conical, rough, with two slight strictures. Length of the three joints = 2 : 2 : 3, breadth = 1 : 4 : 6. Cephalis ovate, with a large, prismatic horn, half as long as the shell. Pores subregular, circular, not double-edged, three times as broad in the inflated abdomen as in the hemispherical thorax. Outer coronal of the wide peristome with twelve to fifteen divergent feet, inner with fifteen to twenty conical feet, which are curved inwards nearly horizontally.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.05, _c_ 0.07; breadth, _a_ 0.025, _b_ 0.1, _c_ 0.15.

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

5. _Lamprocyclas reginæ_, n. sp. (Pl. 74, figs. 11, 12).

Shell campanulate, with two slight strictures. Length of the three joints = 2 : 3 : 3, breadth = 2 : 5 : 6. Cephalis subcylindrical, with about fifteen longitudinal rows of circular pores, separated by prominent, parallel crests, and with a very large sword-like horn, nearly as long as the shell. Thorax hemispherical, smooth, with elegant, circular, hexagonally-framed pores. Abdomen dilated, with similar but larger pores, armed with hook-shaped spines. The two inferior rows of these hooks form the double coronal of the peristome; the feet of the outer are curved downwards, of the inner inwards.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.06, _c_ 0.06; breadth, _a_ 0.04, _b_ 0.1, _c_ 0.12.

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

6. _Lamprocyclas ægles_, Haeckel.

_Podocyrtis ægles_, Ehrenberg, 1854, Mikrogeol., Taf. xxxv. B. B iv. fig.
18.

Shell campanulate, conical, thorny, with two deep strictures. Length of the three joints = 3 : 5 : 5, breadth = 3 : 8 : 11. Cephalis ovate, with a stout, three-sided prismatic horn of twice the {1392}length. Pores subregular, circular, twice as broad in the inflated abdomen as in the campanulate thorax, and four times as broad as in the cephalis. Outer coronal of the wide peristome with fifteen to twenty conical, divergent feet, inner coronal with a smaller number of vertical, parallel, divergent feet.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.05, _c_ 0.05; breadth, _a_ 0.03, _b_ 0.08, _c_ 0.11.

_Habitat._--North Atlantic, depth 1400 fathoms (Berrymann).

Subgenus 2. _Lamprocycloma_, Haeckel.

_Definition._--Feet of the peristome forked or branched.

7. _Lamprocyclas bajaderæ_, n. sp.

Shell campanulate, very similar to the preceding species, but with stronger spines on the abdomen and with different peristome. Length of the three joints = 2 : 2 : 3, breadth = 2 : 6 : 8. Cephalis equal to that of _Lamprocyclas maritalis_ (Pl. 74, figs. 13, 14). Outer coronal of the peristome with fifteen to twenty divergent, pyramidal feet, half as long as the horn; inner coronal with as many longer, vertical feet, which are irregularly forked or branched.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.04, _c_ 0.06; breadth, _a_ 0.04, _b_ 0.12, _c_ 0.16.

_Habitat._--South Pacific, Station 298, depth 2225 fathoms.

Genus 608. _Diplocyclas_,[225] Haeckel, 1881, Prodromus, p. 434.

_Definition._--#Theophormida# (vel Tricyrtida multiradiata aperta) with a double corona of radial solid feet, an upper around the lumbar stricture, a lower around the mouth. No ribs in the shell-wall.

The genus _Diplocyclas_ differs from all the other Theophormida in the possession of a double coronal of radial teeth, an upper between thorax and abdomen, and a lower around the terminal mouth of the latter; it may be regarded as an _Anthocyrtis_, which has formed an abdomen, and repeated the terminal armature. The cephalis bears a single or double apical horn.

1. _Diplocyclas bicorona_, n. sp. (Pl. 59, fig. 8).

Shell slender, campanulate. Length of the three joints = 1 : 3 : 2, breadth = 1 : 4 : 4. Cephalis subspherical, with two divergent horns; the occipital of the same length and forked, the frontal shorter and simple. Thorax campanulate, with six to eight transverse rows of double-edged roundish pores of increasing size. Abdomen cylindrical, with three transverse rows of large {1393}polygonal pores, and a terminal row of very small square pores. Lumbar and terminal coronals of similar shape, each with twenty to thirty short divergent feet.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.06, _c_ 0.04; breadth, _a_ 0.025, _b_ 0.08, _c_ 0.08.

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

2. _Diplocyclas bicincta_, n. sp.

Shell campanulate, in general of the same form as, and similar fenestration to, the preceding species but not so slender, and with different proportions. Length of the three joints = 1 : 4 : 2, breadth = 2 : 5 : 5. Cephalis hemispherical, with a single, conical, simple horn. Pores of the thorax hexagonal, of increasing size (in eight to ten transverse rows). Abdomen with smaller square pores (in four to six rows). The two coronals of the same shape as in Pl. 59, fig. 8.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.08, _c_ 0.04; breadth, _a_ 0.04, _b_ 0.1, _c_ 0.1.

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

3. _Diplocyclas bizonalis_, n. sp.

Shell subconical, with indistinct collar and distinct lumbar stricture. Length of the three joints = 1 : 2 : 3, breadth = 1 : 3 : 4. Cephalis hemispherical, with two divergent conical horns of equal size. Thorax conical, with small, irregular, double-edged pores, and a terminal corona of about nine very large pores. Abdomen truncate, conical, with three to four transverse rows of roundish, quadrangular, very large pores. Lumbar and terminal coronals of similar shape, each with twelve to fifteen triangular divergent feet.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.04, _c_ 0.06; breadth, _a_ 0.02, _b_ 0.06, _c_ 0.08.

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

Subfamily 2. THEOPHÆNIDA, Haeckel, 1881, Prodromus, p. 437.

_Definition._--#Phormocyrtida# with the basal mouth of the shell fenestrated (vel Tricyrtida multiradiata clausa).

Genus 609. _Hexalatractus_,[226] n. gen.

_Definition._--#Theophænida# (vel Tricyrtida multiradiata clausa) with six lateral wings on the abdomen.

The genus _Hexalatractus_, and the following genus _Theophæna_, represent together the small subfamily Theophænida, or those Tricyrtida in which the terminal mouth of the shell is closed by lattice-work, and six or nine lateral apophyses indicate a multiradiate structure. The shell is more or less ovate or spindle-shaped, tapering towards {1394}both poles, and resembles greatly the triradiate _Rhopalocanium_. It may be derived from the latter by interpolation of three secondary or interradial wings between the three primary or perradial apophyses.

1. _Hexalatractus sexalatus_, n. sp.

Shell ovate, smooth, with two distinct strictures, length of the three joints = 3 : 6 : 9, breadth = 4 : 9 : 8. Cephalis subspherical, with a pyramidal horn of twice the length. Thorax campanulate; abdomen inversely conical; both with subregular, circular pores. Six divergent wings arise, beginning from the collar stricture, from the upper half of the shell, with broad triangular base; they are little curved downwards, with the convexity outside, and gradually tapering towards the distal end; the latter lies in the same horizontal plane as the basal apex of the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.09; breadth, _a_ 0.04, _b_ 0.09, _c_ 0.08.

_Habitat._--Central Pacific, Stations 263, depth 2650 fathoms.

2. _Hexalatractus fusiformis_, n. sp. (Pl. 68, fig. 13).

Shell rough, nearly spindle-shaped, with sharp collar and slight lumbar stricture. Length of the three joints = 2 : 5 : 12, breadth = 3 : 8 : 7. Cephalis hemispherical, with a conical horn of the same length. Thorax hemispherical with regular, circular, hexagonally-framed pores. Abdomen inversely conical, with irregular, roundish pores. From the upper half of the abdomen arise, with broad triangular base, six divergent wings, which are nearly straight, and slightly fenestrated at the base; their conical distal ends do not reach the horizontal plane, in which the basal apex of the abdomen lies.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.12; breadth, _a_ 0.03, _b_ 0.08, _c_ 0.07.

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

Genus 610. _Theophæna_,[227] Haeckel, 1881, Prodromus, p. 437.

_Definition._--#Theophænida# (vel Tricyrtida multiradiata clausa) with nine lateral wings on the abdomen.

The genus _Theophæna_ differs from the preceding six-radiate _Hexalatractus_ in the possession of nine lateral wings, and may be derived from the triradiate _Rhopalocanium_ by interpolation of six secondary wings between the three primary apophyses.

1. _Theophæna corona_, n. sp. (Pl. 70, fig. 12).

Shell rough, nearly spindle-shaped, with two sharp strictures. Length of the three joints = 4 : 9 : 16, breadth = 5 : 12 : 10. Cephalis hemispherical, very thick-walled, with a conical horn of {1395}the same length; both covered with numerous small dimples and spinules. Thorax campanulate; abdomen inversely conical; both with regular, circular pores. Thorax with nine thin curved ribs, which in the upper half of the abdomen arise as nine large feet, which are strongly compressed and curved (with the convexity outwards); their distal ends form nine ovate spinulate cones, and lie in the same horizontal plane as the basal apex of the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.09, _c_ 0.16; breadth, _a_ 0.05, _b_ 0.12, _c_ 0.1.

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

2. _Theophæna nonaria_, n. sp.

Shell thorny, ovate, with two slight strictures. Length of the three joints = 1 : 4 : 5, breadth = 1 : 5 : 4. Cephalis subspherical, with a conical horn of half the length. Thorax subspherical, with regular, circular pores and conical spines. Abdomen ovate, smooth, with irregular, roundish pores. In the upper half of the thorax descend nine straight, little divergent ribs, which in the lower half become free, and represent nine slender, conical wings; their distal ends do not reach the horizontal plane in which the basal end of the abdomen lies.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.12, _c_ 0.15; breadth, _a_ 0.03, _b_ 0.14, _c_ 0.12.

_Habitat._--South of Australia, Station 160, surface.

Family LXVII. #THEOCYRTIDA#, n. fam.

_Theocorida et Theocapsida_, Haeckel, 1881, Prodromus, pp. 434, 436.

_Definition._--#Tricyrtida# eradiata. #Cyrtoidea# with a three-jointed shell, divided by two transverse constrictions into cephalis, thorax, and abdomen, without radial apophyses.

The family #Theocyrtida#, composed of the Theocorida and Theocapsida of my Prodromus, comprises those #Cyrtoidea# in which the lattice-shell is three-jointed, and bears no external radial apophyses. The two subfamilies differ in the shape of the terminal mouth, which in the Theocorida is a simple wide opening, in the Theocapsida closed by a lattice-plate. The phylogenetic origin of the Theocyrtida may be found either in the Podocyrtida or in the Sethocyrtida; they may have been derived from the former by reduction and loss of the three primary apophyses, or from the latter by development of an abdomen.

The number of species in this group is very large, and many belong to the most common and widely distributed #Cyrtoidea#. A great number of living and fossil species have already been described by Ehrenberg, the majority being disposed in his genera _Lithocampe_ and _Eucyrtidium_.

The number of genera, however, is comparatively small, and their distinction difficult, since the form of the shell presents no striking differences.

{1396}It exhibits all possible passages, from a flatly expanded or nearly discoidal form with a wide open mouth, to a conical or cylindrical, and by constriction of the terminal mouth to an ovate or spindle-shaped form. By complete closure of the mouth the Theocapsida arise. In some genera remarkable traces of the original triradial structure are preserved. The most interesting of these forms is _Axocorys_, with an internal axial columella, which bears a number of verticils, each with three radial branches.

_Synopsis of the Genera of Theocyrtida._

-------------------------------------------------------------------------
I. Subfamily Theocorida.
Terminal mouth of the abdomen a simple wide opening.
--------------------
Abdomen gradually dilated towards the wide open mouth.
-------------------------------------------------------------------------
Abdomen flatly { With horn, 611. _Theocalyptra_.
expanded, {
discoidal. { No horn, 612. _Cecryphalium_.

{ One horn, 613. _Theoconus_.
Abdomen conical. {
{ Two or more horns, 614. _Lophoconus_.
-------------------------------------------------------------------------
Abdomen cylindrical, of nearly equal breadth throughout its whole length.
Mouth truncate.
-------------------------------------------------------------------------
{ Thorax and abdomen
A single apical horn { of equal breadth, 615. _Theocyrtis_.
on the cephalis. {
{ Thorax much broader than
{ the tubular abdomen, 616. _Theosyringium_.

Two horns or a bunch of horns on the ephalis, 617. _Lophocyrtis_.

No horn on the cephalis, 618. _Tricolocampe_.
-------------------------------------------------------------------------
Abdomen ovate or inversely conical. Mouth more or less constricted.
-------------------------------------------------------------------------
{ Shell-cavity without an
A single apical horn { internal columella, 619. _Theocorys_.
on the cephalis. {
{ Shell-cavity with an
{ axial columella, 620. _Axocorys_.

Two horns or a bunch of horns on the
cephalis, 621. _Lophocorys_.

No horn on the cephalis, 622. _Theocampe_.
-------------------------------------------------------------------------
II. Subfamily Theocapsida.
Terminal mouth closed by a lattice-plate.
-------------------------------------------------------------------------
No latticed septum { An apical horn, 623. _Theocapsa_.
between thorax and {
abdomen. { No horn on the cephalis, 624. _Tricolocapsa_.

A complete latticed septum between thorax
and abdomen, 625. _Phrenocodon_.

Subfamily 1. THEOCORIDA, Haeckel, 1881, Prodromus, p. 434.

_Definition._--#Theocyrtida# with the basal mouth of the shell open (vel Tricyrtida eradiata aperta).

{1397}Genus 611. _Theocalyptra_,[228] Haeckel, 1881, Prodromus, p. 434.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta) with discoidal or flatly expanded abdomen. Cephalis with a single apical horn, or with two divergent horns.

The genus _Theocalyptra_, and the following closely allied genus _Cecryphalium_, differ from all the other Theocorida in the flattened form of the cap-shaped or nearly discoidal shell. The abdomen specially is quite flat, often horizontally expanded, and like the marginal brim of a flat hat. They may be derived from the Dicyrtida _Sethocephalus_ by the development of an abdomen, or from _Corocalyptra_ by loss of the collar wings. The network is usually very delicate, as in the latter. The cephalis of _Theocalyptra_ bears one or two horns.

1. _Theocalyptra veneris_, n. sp.

Shell flatly campanulate, very delicate and fragile, very similar to _Eucecryphalus agnesæ_ (Pl. 59, fig. 3), but without collar spines. Length of the three joints = 1 : 4 : 2, breadth = 1 : 7 : 9. Cephalis hemispherical, with a single bristle-shaped horn of twice the length. Thorax subconical, separated from the flatter abdomen by a deep stricture, with thin bars, and large, subregular, hexagonal meshes, increasing in size towards the smooth mouth-edge.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.07, _c_ 0.04; breadth, _a_ 0.025, _b_ 0.15, _c_ 0.1.

_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, many stations, surface.

2. _Theocalyptra orci_, Haeckel.

_Halicalyptra orci_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 293, Taf. x. figs. 9, 10.

Shell flatly campanulate, very similar to the preceding species in general form and fenestration, but flatter and smaller, with different proportions. Length of the three joints = 7 : 2 : 1, breadth = 1 : 6 : 8. Cephalis hemispherical, very small, with two divergent, bristle-shaped horns of the same length. Abdomen nearly horizontally expanded.

_Dimensions._--Length of the three joints, _a_ 0.015, _b_ 0.04, _c_ 0.01; breadth, _a_ 0.02, _b_ 0.12, _c_ 0.16.

_Habitat._--Indian Ocean, Zanzibar, depth 2200 fathoms (Pullen).

3. _Theocalyptra discoides_, Haeckel.

_Cycladophora discoides_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 68, Taf. xviii. fig. 4.

Shell flatly campanulate, similar to the two preceding species, but not so delicate, with thicker bars, and roundish, not hexagonal meshes. Length of the three joints = 1 : 2 : 2, breadth = 3 : 6 : 9. {1398}Cephalis large, trilobed, with a short, oblique horn of half the length. Thorax campanulate, conical, separated from the abdomen by a circle of smaller pores and a deep stricture. Abdomen flat, discoidal, with three circles of larger pores.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.04, _c_ 0.04; breadth, _a_ 0.06, _b_ 0.12, _c_ 0.18.

_Habitat._--Fossil in Barbados.

4. _Theocalyptra cornuta_, Haeckel.

_Carpocanium cornutum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 287, Taf. ii. fig. 9.

_Halicalyptra cornuta_, Bailey, 1856, Amer. Journ. Sci. and Arts, vol.
xxii. p. 5, pl. i. figs. 13, 14.

_Lophophæna cornuta_, Haeckel, 1862, Monogr. d. Radiol., p. 299.

Shell campanulate-conical, with two sharp strictures. Length of the three joints = 1 : 3 : 1, breadth = 1 : 4 : 5. Cephalis subspherical, with two stout, pyramidal, divergent horns of twice the length. Thorax campanulate, with eight to ten transverse rows of roundish or nearly square pores, increasing in size towards the abdomen, which is flatly expanded, nearly discoidal, separated by a circle of smaller pores; the last circle of pores (on the margin) is larger.

_Dimensions._--Length of the three joints, _a_ 0.025, _b_ 0.09, _c_ 0.03; breadth, _a_ 0.03, _b_ 0.12, _c_ 0.16.

_Habitat._--Arctic Ocean, Kamtschatka (Bailey), Greenland (Ehrenberg).

Genus 612. _Cecryphalium_,[229] Haeckel, 1881, Prodromus, p. 434.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta) with discoidal or flatly expanded abdomen. Cephalis without horn.

The genus _Cecryphalium_ has the same flat, conical, or nearly discoidal shell as the preceding _Theocalyptra_, its ancestral genus, but differs from it in the complete absence of horns on the cephalis.

1. _Cecryphalium lamprodiscus_, n. sp. (Pl. 58, fig. 2).

Shell flatly conical, with two slight strictures. Length of the three joints = 1 : 3 : 2, breadth = 1 : 7 : 11. Cephalis roundish, very small. Thorax conical, with straight lateral outline; its pores irregular, polygonal, increasing in size towards the girdle. Abdomen little flatter than the thorax, forming its direct prolongation, with five to six circular, concentric rows of pores; the first row formed by sixty to eighty very large, oblongish, quadrangular pores, the second row by very small, the third again by larger pores; the outmost rows by very small and numerous pores.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.06, _c_ 0.04; breadth, _a_ 0.02, _b_ 0.14, _c_ 0.22.

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

{1399}2. _Cecryphalium sestrodiscus_, n. sp. (Pl. 58, fig. 1).

Shell very flat, subconical, nearly discoidal, with two distinct strictures. Length of the three joints = 1 : 2 : 1, breadth = 1 : 8 : 10. Cephalis kidney-shaped, very small. Thorax flat, campanulate, with curved lateral outline; its pores irregular, polygonal, increasing in size towards the girdle. Abdomen horizontally expanded, like the brim of a hat, with five to six concentric, circular rows of pores, the pores of the inner rows twice to three times as large as those of the outer rows. (The inner circle of large, oblongish, quadrangular pores, characteristic of the preceding species, is here divided into three concentric rings by two circular hoops.)

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.04, _c_ 0.02; breadth, _a_ 0.02, _b_ 0.15, _c_ 0.2.

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

Genus 613. _Theoconus_,[230] n. gen.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta) with conical abdomen, gradually dilated towards the wide open mouth. Cephalis with a single horn.

The genus _Theoconus_, and the following closely allied _Lophoconus_, differ from the other Theocorida in the conical or campanulate form of the shell; the abdomen is a truncated cone, gradually dilated towards the terminal mouth. The latter is usually truncated, widely open, sometimes with a slightly constricted peristome. The cephalis of _Theoconus_ bears a single apical horn.

Subgenus 1. _Theocorax_, Haeckel.

_Definition._--Pores of the thorax and of the abdomen of nearly equal size and similar form.

1. _Theoconus zancleus_, Haeckel.

_Eucyrtidium zancleum_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 41, Taf. vi. figs. 1-3.

_Eucyrtidium zancleum_, Haeckel, 1862, Monogr. d. Radiol., p. 321.

Shell bell-shaped, nearly conical, smooth. Length of the three joints = 1 : 3 : 4, breadth = 1 : 4 : 6. Cephalis nearly spherical, with a stout, straight, pyramidal horn of the same length. Thorax hemispherical. Abdomen gradually increasing in breadth towards the wide truncated mouth. Pores in all three joints nearly of the same shape, circular, regular, four times as broad as the thin bars.

_Dimensions._--Length of the three joints, _a_ 0.027, _b_ 0.08, _c_ 0.1; breadth, _a_ 0.03, _b_ 0.12, _c_ 0.18.

_Habitat._--Mediterranean (Messina, Naples, Nice, &c.).

{1400}2. _Theoconus ægæus_, Haeckel.

_Eucyrtidium ægæum_, Ehrenberg, 1858, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 31; Mikrogeol., 1854, Taf. xxxv. a, xix. a, fig. 5.

_Eucyrtidium ægæum_, Haeckel, 1862, Monogr. d. Radiol., p. 329.

Shell flatly bell-shaped, nearly conical. Length of the three joints = 2 : 5 : 3; breadth = 1 : 7 : 8. Cephalis ovate, with a stout, straight, pyramidal horn of the same length. Thorax flat, bell-shaped. Abdomen with increasing breadth towards the wide truncated mouth. Pores in all three joints nearly of the same shape, regular, circular, three times as broad as the bars.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.03; breadth, _a_ 0.016, _b_ 0.07, _c_ 0.08.

_Habitat._--Mediterranean (Coast of Greece and Sicily), surface.

3. _Theoconus zanguebaricus_, Haeckel.

_Eucyrtidium zanguebaricum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 293, Taf. ix. fig. 22.

Shell bell-shaped. Length of the three joints = 1 : 2 : 1, breadth = 1 : 3 : 4. Cephalis ovate, with a straight, pyramidal horn of half the length. Thorax hemispherical, without collar stricture, but with evident girdle stricture. Abdomen dilated towards the wide truncated mouth. Pores regular, hexagonal, of nearly equal size and form, four to six times as broad as the thin bars.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.03; breadth, _a_ 0.024, _b_ 0.09, _c_ 0.11.

_Habitat._--Indian Ocean (off Zanzibar), Pullen, depth 2200 fathoms.

4. _Theoconus campanulatus_, Haeckel.

? _Eucyrtidium campanulatum_, Ehrenberg, 1858, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 241.

_Eucyrtidium campanulatum_, Haeckel, 1862, Monogr. d. Radiol., p. 329.

Shell bell-shaped, smooth. Length of the three joints = 2 : 3 : 7, breadth = 3 : 7 : 10. Cephalis small, spherical, with a short, conical, oblique horn of the same length. Thorax hemispherical, with an external girdle stricture, prolonged into the truncated, barrel-shaped abdomen, which is a little constricted at the very wide mouth. Pores small and very numerous, regular, circular, twice to three times as broad as the bars.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.03, _c_ 0.07; breadth, _a_ 0.03, _b_ 0.07, _c_ 0.1.

_Habitat._--North Atlantic, Station 352, surface.

5. _Theoconus orthoconus_, n. sp.