Chapter XXIV: Section III: TRICYRTIDA, Haeckel, 1881, Prodromus, p. 426, 434 (5)

Shell perfectly conical, smooth. Length of the three joints = 1 : 2 : 3, breadth = 1 : 2 : 4. Cephalis hemispherical, with a strong, straight, conical horn of the same length. Thorax conical, without external girdle stricture, prolonged into the truncated, conical abdomen, which is gradually {1401}dilated into a very wide mouth. Pores small, of nearly equal size and similar form, of the same breadth as the bars.

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

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

Subgenus 2. _Theocorbis_, Haeckel.

_Definition._--Pores of the thorax and of the abdomen of different sizes or dissimilar forms.

6. _Theoconus jovis_, n. sp. (Pl. 69, fig. 4).

Shell bell-shaped, nearly conical. Length of the three joints = 5 : 6 : 7, breadth = 4 : 10 : 14. Cephalis nearly cylindrical, large, little curved, with a very large, oblique, pyramidal horn, as long as the two first joints together. Thorax and the broader abdomen irregularly bell-shaped, dilated towards the wide mouth. Pores circular, somewhat irregularly disposed, gradually increasing in size towards the mouth.

_Dimensions._--Length of the three joints, _a_ 0.05, _b_ 0.06, _c_ 0.07; breadth, _a_ 0.04, _b_ 0.1, _c_ 0.14.

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

7. _Theoconus junonis_, n. sp. (Pl. 69, fig. 7).

Shell nearly conical. Length of the three joints = 4 : 5 : 8, breadth = 3 : 8 : 11. Cephalis ovate, with a large apical opening at the base of the vertical compressed horn, which has about the same length. Thorax and the broader abdomen together conical, gradually dilated towards the wide mouth. Thorax with a bosom-like protuberance on one side. Pores circular, gradually increasing in size.

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

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

8. _Theoconus longicornis_, n. sp.

Shell conical, thorny. Length of the three joints = 1 : 2 : 4, breadth = 1 : 3 : 6. Cephalis nearly spherical, with a very large, cylindrical, perpendicular, straight horn, once and a half to twice as long as the whole shell. Thorax conical. Abdomen nearly hemispherical, with wide open mouth. Pores circular, four to six times as broad in the thick-walled spiny abdomen as in the thin-walled rough thorax.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.12; breadth, _a_ 0.03, _b_ 0.09, _c_ 0.18.

_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms; also fossil in Barbados.

{1402}9. _Theoconus ampullaceus_, Haeckel.

_Lithocampe ampullacea_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 66, Taf. iv. fig. 1.

_Theocorys ampullacea_, Haeckel, 1881, Prodromus, p. 434.

Shell bell-shaped, nearly conical, thorny. Length of the three joints = 3 : 4 : 10; breadth = 4 : 8 : 15. Cephalis subspherical, with a stout lateral horn of the same length. Thorax hemispherical, rough. Abdomen subspherical, widely truncated at both poles, spiny. Pores regular, circular, three to four times as broad in the thick-walled abdomen as in the thin-walled thorax. (Differs from the similar preceding species in the smaller horn and the two deeper strictures of the shell.)

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.04, _c_ 0.1; breadth, _a_ 0.04, _b_ 0.08, _c_ 0.15.

_Habitat._--Fossil in Barbados.

10. _Theoconus amplus_, Haeckel.

? _Podocyrtis ampla_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 80, Taf. xvi. fig. 7.

? _Podocyrtis ampla_, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi. p. 539, Taf. xxxiii. fig. 16.

? _Eucyrtidium amplum_, Ehrenberg, 1873, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 248.

Shell conical, smooth, with two broad internal annular septa. Length of the three joints = 1 : 3 : 4, breadth = 1 : 4 : 5. Cephalis subspherical, with a very large, straight, conical horn of the same breadth, which is as long as the conical thorax. Pores regular, circular, twice as broad in the truncate, gradually dilated abdomen as in the thorax.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.09, _c_ 0.12; breadth, _a_ 0.03, _b_ 0.12, _c_ 0.15.

_Habitat._--Fossil in Barbados.

11. _Theoconus ariadnes_, n. sp.

Shell conical, nearly bell-shaped, smooth. Length of the three joints = 1 : 2 : 3, breadth = 1 : 3 : 5. Cephalis subspherical, with a conical spine of about the same length. Thorax hemispherical, thin-walled. Abdomen conical, slightly constricted at the wide open mouth. Pores regular, circular, twice as large in the thick-walled abdomen as in the thin-walled thorax.

_Dimensions._--Length of the three joints, _a_ 0.018 to 0.022, _b_ 0.03 to 0.035, _c_ 0.06 to 0.07; breadth, _a_ 0.015 to 0.02, _b_ 0.04 to 0.06, _c_ 0.07 to 0.09.

_Habitat._--Cosmopolitan; Atlantic, Indian, and Pacific Oceans, common, surface.

12. _Theoconus dionysius_, Haeckel.

_Thyrsocyrtis dionysia_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xii. fig. 5.

_Thyrsocyrtis jacchia_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xii. fig. 7.

Shell bell-shaped, smooth. Length of the three joints = 1 : 3 : 5, breadth = 1 : 4 : 5. Cephalis subspherical, with a conical, irregularly denticulate horn of twice or thrice the length. Thorax {1403}inflated, nearly spherical, truncate at both poles, separated by a deep stricture from the cephalis, as well as from the conical abdomen, which is dilated gradually towards the wide mouth. Pores in the thorax subregular, circular, in the abdomen twice to four times larger, and irregular.

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

_Habitat._--Fossil in Barbados.

13. _Theoconus laterna_, n. sp.

Shell conical, smooth. Length of the three joints = 1 : 2 : 4, breadth = 1 : 2 : 4. Cephalis small, ovate, with a strong, pyramidal, vertical horn three times the length. Thorax hemispherical, with subregular, circular, hexagonally-framed pores. Abdomen truncate, conical, with only fifteen to twenty very large, irregular, polygonal pores, which are separated by very thick bars of the same breadth as the horn.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.12; breadth, _a_ 0.03, _b_ 0.07, _c_ 0.12.

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

14. _Theoconus ficus_, Haeckel.

_Eucyrtidium ficus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. xi. fig. 19.

_Theocorys ficus_, Haeckel, 1881, Prodromus, p. 434.

Shell conical, pear-shaped, smooth. Length of the three joints = 1 : 5 : 20, breadth = 2 : 10 : 25. Cephalis very small, ovate, with a conical, straight horn three times the length. Thorax quite conical, with solid wall, without pores. Abdomen very large, nearly spherical, truncate at both poles, little constricted at the very wide mouth; its pores subregular, circular, about three times as broad as the bars. (This species is intermediate between the genera _Theoconus_ and _Theocorys_.)

_Dimensions._--Length of the three joints, _a_ 0.01, _b_ 0.05, _c_ 0.2; breadth, _a_ 0.02, _b_ 0.1, _c_ 0.25.

_Habitat._--Fossil in Barbados.

Genus 614. _Lophoconus_,[231] n. gen.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta) with conical abdomen gradually dilated towards the wide open mouth. Cephalis with two or more horns or a corona of horns.

The genus _Lophoconus_ has the same conical shell with truncate mouth as _Theoconus_, and differs from it only in the armature of the cephalis, bearing either two large divergent horns (usually a larger occipital and a smaller frontal horns), or a bunch or corona of numerous divergent horns.

{1404}1. _Lophoconus antilope_, Haeckel.

_Eucyrtidium antilope_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 291, Taf. ix. fig. 18.

Shell conical, smooth, with two slight strictures. Length of the three joints = 1 : 3 : 8, breadth = 2 : 4 : 8. Cephalis hemispherical, with two divergent, pyramidal horns of twice the length. Thorax campanulate. Abdomen gradually dilated towards the wide open mouth. Pores very small and numerous, regular, hexagonal.

_Dimensions._--Length of the three joints, _a_ 0.015, _b_ 0.05, _c_ 0.12; breadth, _a_ 0.025, _b_ 0.07, _c_ 0.12.

_Habitat._--Indian Ocean; between Aden and Socotra (Haeckel); Zanzibar (Pullen).

2. _Lophoconus hexagonalis_, n. sp.

Shell campanulate, conical, spiny, with two sharp strictures. Length of the three joints = 1 : 2 : 4, breadth = 1 : 3 : 6. Cephalis hemispherical, with numerous conical spines of different sizes, the largest of twice the length. Thorax campanulate, with smaller spines. Abdomen inflated, dilated towards the wide mouth. Pores large, three or four times as broad as the bars, subregular, hexagonal.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.09; breadth, _a_ 0.03, _b_ 0.07, _c_ 0.12.

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

3. _Lophoconus cornutella_, n. sp.

Shell slender, conical, smooth, without external strictures, but with two internal, annular septa. Length of the three joints = 1 : 2 : 6, breadth = 1 : 2 : 4. Cephalis ovate, with two stout, divergent, conical horns of three times the length. Thorax and abdomen together conical, gradually dilated towards the wide truncate mouth. Pores regular, circular, quincuncial.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.12; breadth, _a_ 0.02, _b_ 0.04, _c_ 0.08.

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

4. _Lophoconus apiculatus_, Haeckel.

_Eucyrtidium apiculatum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. x. fig. 10.

Shell campanulate, conical, thorny, with two distinct strictures. Length of the three joints = 1 : 2 : 2, breadth = 1 : 3 : 4. Cephalis subspherical, with a bunch of eight to twelve divergent, conical horns, the largest of which are longer than the cephalis. The regular, circular pores are in the campanulate thorax scarcely half as broad as in the truncate, gradually dilated abdomen.

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

_Habitat._--Fossil in Barbados.

{1405}5. _Lophoconus cervus_, Haeckel

? _Eucyrtidium cervus_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 291, Taf. ix. fig. 21.

Shell conical, smooth, without external stricture, but with two internal annular septa. Length of the three joints = 1 : 2 : 4, breadth = 1 : 3 : 6. Cephalis campanulate, with two to six divergent, partly ramified horns. Pores in the thorax regular, circular, in the abdomen three to four times as large, regular, hexagonal.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.04, _c_ 0.08; breadth, _a_ 0.02, _b_ 0.06, _c_ 0.12.

_Habitat._--Indian Ocean, Cocos Islands (Rabbe), surface (? Zanzibar, 2200 fathoms, Pullen).

6. _Lophoconus rhinoceros_, n. sp. (Pl. 69, fig. 2).

Shell campanulate, conical, rough, with two sharp strictures. Length of the three joints = 1 : 2 : 3, breadth = 1 : 3 : 4. Cephalis subspherical, with numerous very small pores, and two stout, divergent, pyramidal horns, the major of which is longer, the minor shorter, than the cephalis. Thorax campanulate, with small, regular, circular pores. Abdomen inflated, with thickened margin at the wide open mouth, and with irregular, roundish pores, twice to four times as broad as those of the thorax.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.05, _c_ 0.09; breadth, _a_ 0.04, _b_ 0.09, _c_ 0.12.

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

Genus 615. _Theocyrtis_,[232] n. gen.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta) with cylindrical abdomen, and wide open truncate mouth. Cephalis with a single horn.

The genus _Theocyrtis_ and the three following closely allied genera differ from the other Theocorida in the cylindrical form of the slender abdomen, which is of equal breadth nearly throughout its whole length. The terminal mouth is wide open, usually truncate, and of the same breadth; sometimes slightly constricted. The cephalis of Theocyrtis bears a single horn.

Subgenus 1. _Theocorypha_, Haeckel.

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

1. _Theocyrtis trachelius_, Haeckel.

_Eucyrtidium trachelius_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 293, Taf. vii. fig. 8.

Shell thin-walled and very fragile, smooth. Length of the three joints = 2 : 8 : 7, breadth = 2 : 9 : 8. Cephalis subspherical, with a straight, conical horn of the same length, separated by a {1406}slender neck from the inflated, subspherical thorax. Abdomen cylindrical, with a wide open, truncate mouth. Pores subregular, hexagonal, of equal size, four to six times as broad as the thin, thread-like bars.

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

_Habitat._--Tropical Pacific, many Stations (200, 224, 271, &c.), surface, and in various depths.

2. _Theocyrtis barbadensis_, Haeckel.

_Eucyrtidium barbadense_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. ix. fig. 7.

Shell thin-walled, smooth. Length of the three joints = 2 : 4 : 5, breadth, 2 : 5 : 4. Cephalis ovate or conical, with a strong, conical horn, without external stricture, dilated into the campanulate thorax. Abdomen cylindrical, with a wide open, truncate mouth. Pores subregular, circular, quincuncially disposed, of about the same breadth as the bars.

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

_Habitat._--Fossil in the Tertiary rocks of Barbados.

3. _Theocyrtis cylindrica_, Haeckel.

_Eucyrtidium cylindricum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. x. fig. 1.

Shell elongate, cylindrical, straight, smooth. Length of the three joints = 1 : 2 : 6, breadth = 1 : 3 : 3. Cephalis hemispherical, with a thick, pyramidal horn of the same length (the edges of the horn giving to it the appearance of being composed of two converging spines). Thorax truncated, conical. Abdomen perfectly cylindrical, much elongated. Pores subregular, circular, twice as broad as the bars, quincuncially disposed. Mouth wide open, truncate.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.04, _c_ 0.12; breadth, _a_ 0.03, _b_ 0.06, _c_ 0.06.

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

4. _Theocyrtis elegans_, Haeckel.

_Eucyrtidium elegans_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. xi. fig. 12.

? _Eucyrtidium pusillum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 72, Taf. xi. fig. 6

Shell slender, cylindrical, straight, smooth. Length of the three joints = 1 : 2 : 7, breadth = 1 : 3 : 3. Cephalis subconical, with a small conical horn. Thorax campanulate, conical. Abdomen cylindrical, very slender. Pores subregular, circular, small, disposed in transverse rows, three in the thorax, six to eight in the abdomen. Mouth wide open, truncate.

_Dimensions._--Length of the three joints, _a_ 0.01, _b_ 0.02, _c_ 0.07; breadth, _a_ 0.015, _b_ 0.03, _c_ 0.03.

_Habitat._--Fossil in Barbados and Sicily.

{1407}5. _Theocyrtis paupera_, Haeckel.

_Eucyrtidium pauperum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 72, Taf. xi. fig. 13.

Shell slender, cylindrical, smooth. Length of the three joints = 1 : 2 : 6, breadth = 1 : 3 : 3. Cephalis hemispherical, with a stout conical horn of twice the length. Thorax truncate, conical. Abdomen cylindrical. Pores very small, regular, circular, disposed in transverse rows, one or two in the thorax, three to five in the abdomen. (Distance between the rows twice as great as in the preceding nearly related species.) Mouth wide open, truncate.

_Dimensions._--Length of the three joints, _a_ 0.01, _b_ 0.02, _c_ 0.06; breadth, _a_ 0.015, _b_ 0.03, _c_ 0.03.

_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms; also fossil in Barbados and Sicily.

6. _Theocyrtis microtheca_, Haeckel.

_Eucyrtidium microtheca_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 72, Taf. xi. fig. 10.

_Eucyrtidium hillaby_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 72, Taf. xi. fig. 8.

Shell cylindrical, a little rough. Length of the three joints = 1 : 3 : 4, breadth = 1 : 3 : 3. Cephalis subspherical, with a small conical horn. Thorax hemispherical or campanulate. Abdomen cylindrical, with wide open truncate mouth. Pores subregular, circular, quincuncially disposed, of medium size, rudimentary or wanting in the cephalis.

_Dimensions._--Length of the three joints, _a_ 0.015 to 0.02, _b_ 0.03 to 0.05, _c_ 0.05 to 0.08; breadth, _a_ 0.02 to 0.025, _b_ 0.05 to 0.06, _c_ 0.05 to 0.06.

_Habitat._--Central Pacific, Stations 263 to 274, depth 2350 to 2925 fathoms; also fossil in Barbados.

Subgenus 2. _Theocorusca_, Haeckel.

_Definition._--Pores of the thorax and the abdomen of different sizes or forms.

7. _Theocyrtis macroceros_, n. sp. (Pl. 69, fig. 13).

Shell almost cylindrical, smooth. Length of the three joints = 1 : 2 : 5, breadth = 2 : 3 : 4. Cephalis hemispherical, with a very large cylindrical horn, once or twice as long as the shell. Thorax truncate, hemispherical. Abdomen cylindrical, only slightly contracted towards both ends. Two girdle strictures deep. Pores small, subregular, circular, more irregular and twice to three times as large in the abdomen as in the thorax, disposed in transverse rows, five to six in the thorax, eight to ten in the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.02 to 0.03, _b_ 0.04 to 0.05, _c_ 0.1 to 0.12; breadth, _a_, 0.04, _b_ 0.07, _c_ 0.08.

_Habitat._--South Atlantic, Station 335, depth 1425 fathoms; also fossil in Barbados.

{1408}8. _Theocyrtis ptychodes_, n. sp. (Pl. 69, fig. 8).

Shell almost cylindrical, smooth. Length of the three joints = 1 : 3 : 3, breadth = 2 : 4 : 4. Cephalis hemispherical, with a large, conical, curved horn of twice the length. Thorax very large, inflated, campanulate, thick-walled. Abdomen cylindrical, with a thin folded wall (like a petticoat), the thickness of which decreases gradually towards the wide truncate mouth. Pores subregular, circular, and quincuncially disposed in the two first joints, irregular and larger in the abdomen, forming longitudinal series between the folds.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.1, _c_ 0.11; breadth, _a_ 0.05, _b_ 0.12, _c_ 0.12.

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

9. _Theocyrtis aspera_, Haeckel.

_Eucyrtidium asperum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. viii. fig. 15.

Shell almost cylindrical, with rough or thorny surface. Length of the three joints = 1 : 3 : 5, breadth = 1 : 5 : 5. Cephalis subspherical, small, with a short conical horn. Thorax hemispherical, inflated. Abdomen cylindrical, with wide truncate mouth. Pores in the thorax subregular, circular, quincuncially disposed, in the abdomen irregular roundish, two to four times as large.

_Dimensions._--Length of the three joints, _a_ 0.015 to 0.02, _b_ 0.06 to 0.07, _c_ 0.08 to 0.1; breadth, _a_ 0.02, _b_ 0.1, _c_ 0.1.

_Habitat._--Tropical Atlantic, Station 338, depth 1990 fathoms; fossil in Barbados.

10. _Theocyrtis proserpinæ_, n. sp.

Shell almost cylindrical, smooth. Length of the three joints = 3 : 6 : 9, breadth = 2 : 8 : 7. Cephalis subspherical, with a stout conical horn. Thorax campanulate. Abdomen cylindrical. Pores regular, circular, quincuncially disposed, double-edged in the thorax, and three to four times as large as in the cephalis and the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.09; breadth, _a_ 0.02, _b_ 0.08, _c_ 0.07.

_Habitat._--North Pacific, Stations 244 to 253, depth 2050 to 3125 fathoms.

11. _Theocyrtis oenophila_, Haeckel.

_Thyrsocyrtis oenophila_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xii. fig. 8.

Shell in the apical half conical, in the lower cylindrical. Length of the three joints = 2 : 5 : 6, breadth = 3 : 8 : 7. Cephalis subspherical, with a large prismatic horn, which is bulbous at the base, and armed with three teeth at the distal apex. Thorax conical, constricted at the base, with subregular, circular, quincuncial pores. Abdomen cylindrical, with a coronal of nine large {1409}roundish pores beyond the lumbar stricture, and two to four succeeding transverse rows of irregular, roundish, smaller pores. Mouth widely open, truncated.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.06; breadth, _a_ 0.03, _b_ 0.08, _c_ 0.07.

_Habitat._--Fossil in Barbados.

Genus 616. _Theosyringium_, Haeckel,[233] 1881, Prodromus, p. 434.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta) with cylindrical abdomen, which is much narrower than the inflated thorax, and forms a slender, narrow tube, with truncated mouth. Cephalis with a single horn.

The genus _Theosyringium_ differs from the closely allied _Theocyrtis_, its ancestral form, in the wide inflated thorax, which is much broader than the narrow tubular abdomen. The mouth of the latter is small and truncate.

1. _Theosyringium tibia_, n. sp. (Pl. 68, fig. 4).

Shell rough, very slender, with two distinct strictures. Length of the three joints = 1 : 3 : 4, breadth = 1 : 2 : 1. Cephalis ovate, with a conical horn of the same length. Thorax ellipsoidal. Abdomen cylindrical, as long as the two former joints together. Pores subregular, circular.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.09, _c_ 0.12; breadth, _a_ 0.03, _b_ 0.06, _c_ 0.02.

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

2. _Theosyringium pipetta_, n. sp. (Pl. 68, fig. 5).

Shell rough, inflated, with two sharp strictures. Length of the three joints = 2 : 7 : 9, breadth = 2 : 7 : 2. Cephalis conical, with a slender horn of half the length. Thorax subglobose. Abdomen cylindrical, as long as the two former joints together. Pores subregular, circular.

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

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

3. _Theosyringium siphonium_, n. sp.

Shell rough, inflated, with two deep strictures. Length of the three joints = 1 : 3 : 3, breadth = 1 : 2 : 1. Cephalis subspherical, with a stout pyramidal horn of twice the length. Thorax broad ovate. Abdomen slender, inversely conical, as long as the thorax, and one-third as broad as the base. Pores subregular, circular, hexagonally framed, (Similar to _Eusyringium conosiphon_, Pl. 78, fig. 10, but only with two strictures and three joints.)

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.1, _c_ 0.1; breadth, _a_ 0.03, _b_ 0.07, _c_ 0.025.

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

{1410}4. _Theosyringium tubulus_, Haeckel.

_Eucyrtidium tubulus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 72, Taf. xi. fig. 6.

Shell smooth, slenderly spindle-shaped, with two slight strictures. Length of the three joints = 2 : 10 : 8, breadth = 3 : 6 : 3. Cephalis hemispherical, hyaline, with a stout, pyramidal horn of the same length. Thorax spindle-shaped. Abdomen inversely conical, half as long as the thorax prolonged into a slender, cylindrical tube. Pores subregular, circular.

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

_Habitat._--Fossil in Barbados.

Genus 617. _Lophocyrtis_,[234] n. gen.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta) with cylindrical abdomen, and wide open truncate mouth. Cephalis with two horns, or a bunch of horns.

The genus _Lophocyrtis_ differs from its ancestral form _Theocyrtis_ only in the armature of the cephalis, bearing instead of a single horn either two divergent horns, or a bunch, or coronal of numerous spines. The slender abdomen is in both genera cylindrical, with wide open mouth.

1. _Lophocyrtis holothuria_, n. sp.

Shell smooth, slender, with two distinct strictures. Length of the three joints = 1 : 2 : 4, breadth = 2 : 4 : 3. Cephalis hemispherical, with a bunch of five divergent, conical horns, the middle of which is larger and vertical, nearly as long as the thorax. Thorax campanulate, half as long as the cylindrical abdomen. Mouth truncate. Pores regular, circular, quincuncial. (Similar to _Theocyrtis cylindrica_, but with different cephalis and thorax.)

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.05, _c_ 0.1; breadth, _a_ 0.04, _b_ 0.07, _c_ 0.06.

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

2. _Lophocyrtis stephanophora_, Haeckel.

_Eucyrtidium stephanophorum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin p. 72, Taf. viii. fig. 14.

Shell smooth, slender, with deep collar and indistinct lumbar stricture. Length of the three joints = 1 : 2 : 4, breadth = 1 : 3 : 3. Cephalis subspherical, with very small circular pores, and a corona of three to nine short conical spines. Thorax campanulate, with regular, circular pores, which are half or one-third as broad as those of the cylindrical abdomen.

_Dimensions._--Length of the three joints, _a_ 0.025, _b_ 0.05, _c_ 0.09; breadth, _a_ 0.025, _b_ 0.06, _c_ 0.06.

_Habitat._--Fossil in Barbados.

{1411}3. _Lophocyrtis synapta_, n. sp. Pl. 68, fig. 15.

Shell spiny, with two sharp strictures. Length of the three joints = 5 : 10 : 6, breadth = 4 : 9 : 7. Cephalis large, ovate, with numerous (twenty to thirty or more) conical, radially divergent spines of different sizes, the largest about as long as the cephalis. Thorax subconical, with numerous short, conical, divergent spines, which are directed downwards. Abdomen smooth, cylindrical. The irregular, polygonal pores are separated by thin bars, and in the thorax are twice to four times as broad as in the first and last joints.

_Dimensions._--Length of the three joints, _a_ 0.05, _b_ 0.1, _c_ 0.06; breadth, _a_ 0.04, _b_ 0.09, _c_ 0.07.

_Habitat._--Indian Ocean, Maldive Islands (Haeckel), surface.

4. _Lophocyrtis coronata_, Haeckel.

_Eucyrtidium coronatum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. x. fig. 9.

Shell smooth, cylindrical, with two deep strictures. Length of the three joints = 4 : 3 : 4, breadth = 4 : 5 : 4. Cephalis subspherical, large, of about the same size and form as the thorax, with a coronal of four to eight short, conical spines on the apex. Pores in the two first joints irregular, roundish, twice to four times as broad as the small, circular pores of the cylindrical abdomen, which are disposed in four to eight transverse rows.

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

_Habitat._--Central Pacific, Station 273, depth 2350 fathoms; fossil in Barbados.

5. _Lophocyrtis biaurita_, Haeckel.

_Eucyrtidium biauritum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. x. fig. 8.

_Eucyrtidium biauritum_, Bütschli, 1882, Zeitschr. f. wiss. Zool., p.
540, Taf. xxxiii. fig. 38, _a_-_f_.

Shell smooth, with two distinct strictures. Length of the three joints = 1 : 6 : 3, breadth = 2 : 5 : 4. Cephalis small, hemispherical, hyaline, with two large, divergent, curved horns of three times the length. Thorax ovate, with few small, widely scattered pores. Abdomen cylindrical, without pores.

_Dimensions._--Length of the three joints, _a_ 0.015, _b_ 0.06, _c_ 0.03; breadth, _a_ 0.02, _b_ 0.05, _c_ 0.04.

_Habitat._--Fossil in Barbados.

Genus 618. _Tricolocampe_,[235] Haeckel, 1881, Prodromus, p. 434.

_Definition_.--#Theocorida# (vel Tricyrtida eradiata aperta), with cylindrical abdomen, and wide open truncate mouth. Cephalis without horn.

The genus _Tricolocampe_ differs from its ancestral genus, _Theocyrtis_, in the loss of the cephalic horn; it has the same cylindrical form of the slender abdomen, and a wide {1412}open terminal mouth of the same breadth. The whole shell is more or less cylindrical, (sometimes conical in the upper part), with two distinct external strictures, or internal annular septa.

Subgenus 1. _Tricolocampium_, Haeckel.

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

1. _Tricolocampe cylindrica_, n. sp. (Pl. 66, fig. 21).

Shell nearly cylindrical, smooth. Length of the three joints = 2 : 3 : 15, breadth = 3 : 4 : 5. Cephalis hemispherical, with numerous very small pores. Thorax and abdomen cylindrical, of about equal breadth, with equal, circular pores, disposed regularly in transverse rows, three to four rows in the thorax, ten to twelve in the abdomen. Mouth wide open, not constricted.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.03, _c_ 0.15; breadth, _a_ 0.03, _b_ 0.04, _c_ 0.05.

_Habitat._--Central Pacific, Stations 265 to 274, depth 2350 to 2925 fathoms.

2. _Tricolocampe pupa_, Haeckel.

_Eucyrtidium pupa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 293, Taf. vii. fig. 16.

Shell nearly cylindrical, smooth. Length of the three joints = 2 : 2 : 8, breadth = 2 : 3 : 3. Cephalis subspherical, with four larger pores. Thorax and abdomen cylindrical, of about equal breadth, with equal, very small pores, disposed regularly in transverse rows, two rows in the thorax, eight to ten in the abdomen. Mouth wide open, a little constricted.

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

_Habitat._--Tropical Pacific (Philippine Sea), Station 206, depth 2100 fathoms.

3. _Tricolocampe polyzona_, n. sp. (Pl. 66, fig. 19).

Shell nearly cylindrical, thick-walled. Length of the three joints = 4 : 4 : 12, breadth = 8 : 9 : 9. Cephalis obtuse, conical. Thorax barrel-shaped. Abdomen in the middle part a little constricted. Pores very numerous, subregular, disposed regularly in transverse rows, six to eight in the cephalis, eight to ten in the thorax, twelve to fifteen in the abdomen. Mouth rather constricted, only half as broad as the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.04, _c_ 0.12; breadth, _a_ 0.08, _b_ 0.09, _c_ 0.09.

_Habitat._--Central Pacific, Stations 266 to 272, depth 2425 to 2925 fathoms; also fossil in the Nicobars and in Barbados.

{1413}4. _Tricolocampe stenozona_, n. sp. (Pl. 66, fig. 20).

Shell nearly cylindrical, thin-walled. Length of the three joints = 5 : 4 : 9, breadth = 6 : 8 : 9. Form of the three joints and disposition of their pores nearly equal to the preceding species; but the proportion of the joints is different, the shell more delicate, and the mouth more widely open, and nearly as broad as the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.05, _b_ 0.04, _c_ 0.09; breadth, _a_ 0.06, _b_ 0.08, _c_ 0.09.

_Habitat._--North Pacific, Station 256, depth 2950 fathoms.

5. _Tricolocampe amphizona_, n. sp. (Pl. 66, fig. 17).

Shell mitre-shaped, very thick-walled. Length of the three joints = 2 : 1 : 1, breadth nearly uniform. Cephalis obtuse, conical, as long as the two other cylindrical joints together (probably composed of several united joints). Pores subregular, disposed in transverse rows, six to eight in the cephalis, two in the thorax, and two in the abdomen. Mouth widely open.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.02, _c_ 0.02; breadth, _a_ 0.04, _b_ 0.05, _c_ 0.05.

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

6. _Tricolocampe panthera_, Haeckel.

_Eucyrtidium panthera_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 72, Taf. xi. fig. 18.

Shell mitre-shaped or nearly cylindrical, thick-walled. Length of the three joints = 1 : 2 : 3, breadth = 1 : 2 : 2. Cephalis subspherical. Thorax campanulate. Abdomen cylindrical. Pores in all three joints irregular, roundish, of different sizes, irregularly disposed. Mouth widely open, truncated, not constricted.

_Dimensions._--Length of the three joints, _a_ 0.015 to 0.02, _b_ 0.04 to 0.05, _c_ 0.06 to 0.08; breadth about _a_ 0.02, _b_ and _c_ 0.05.

_Habitat._--Cosmopolitan; Atlantic, Pacific; also fossil in Barbados.

Subgenus 2. _Tricolocamptra_, Haeckel.

_Definition._--Pores of the thorax and the abdomen of different sizes or forms.

7. _Tricolocampe urnula_, n. sp. (Pl. 66, fig. 22).

Shell cylindrical, with obtuse conical apex, smooth. Length of the three joints = 2 : 3 : 10, breadth = 2 : 3 : 6. Cephalis subspherical. Thorax barrel-shaped. Abdomen cylindrical with slightly constricted wide mouth. Pores irregular, roundish, three to four times as broad in the abdomen as in the thorax, irregularly disposed.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.03, _c_ 0.1; breadth, _a_ 0.025, _b_ 0.035, _c_ 0.06.

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

{1414}8. _Tricolocampe doliolum_, n. sp.

Shell cylindrical, with hemispherical apex, rough. Length of the three joints = 1 : 3 : 5, breadth = 1 : 2 : 3. Cephalis spherical. Thorax and abdomen cylindrical, of nearly equal breadth. Mouth widely open, not constricted. Pores irregular, roundish, in the abdomen three to four times as large as in the thorax, disposed in oblique rows.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.09, _c_ 0.16; breadth, _a_ 0.03, _b_ 0.05, _c_ 0.09.

_Habitat._--Fossil in Barbados.

9. _Tricolocampe cingulata_, n. sp.

Shell subcylindrical, with obtuse conical apex, thick-walled. Length of the three joints = 2 : 3 : 11, breadth = 3 : 7 : 8. Cephalis hemispherical, not separated externally from the short conical thorax, but with internal collar septum. Abdomen cylindrical, with wide open, non-constricted mouth. Pores in the thorax narrow, obliquely ascending, in the abdomen twice as large, circular, arranged in ten to twelve regular transverse rows, separated by slight strictures. Lumbar septum nearly complete.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.03, _c_ 0.1 to 0.12; breadth, _a_ 0.03, _b_ 0.07, _c_ 0.08.

_Habitat._--Fossil in Barbados, and in Tertiary rocks of Sicily; living in the depths of the Atlantic and Central Pacific, Station 348, depth 2450 fathoms; Station 268, depth 2900 fathoms.

10. _Tricolocampe arcta_, Haeckel.

? _Eucyrtidium arctum_, Ehrenberg, 1858, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 33.

? _Lithocampe arcta_, Haeckel, 1862, Monogr. d. Radiol., p. 317.

Shell subcylindrical, with obtuse conical apex. Length of the three joints = 1 : 2 : 4, breadth = 1 : 2 : 2. Cephalis subspherical. Thorax campanulate, separated by a deep collar, but a slight lumbar stricture. Abdomen cylindrical, with wide truncate mouth. Pores in the thorax narrow, obliquely ascending, in the abdomen half as large, very small, and densely disposed in six to eight regular transverse rows.

_Dimensions._--Length of the three joints, _a_ 0.022, _b_ 0.045, _c_ 0.09; breadth, _a_ 0.026, _b_ 0.05, _c_ 0.05.

_Habitat._--Central Pacific, Station 266 to 274, depth 2350 to 2925 fathoms.

Genus 619. _Theocorys_,[236] Haeckel, 1881, Prodromus, p. 434.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta) with ovate abdomen, broader than the constricted mouth. Cephalis with a single horn.

The genus _Theocorys_ and the two following closely allied genera, united formerly with _Eucyrtidium_, differ from the preceding Theocorida in the constriction of the {1415}peristome, so that the inflated abdomen is broader than the terminal mouth. They represent, therefore, the transition to the Theocapsida, with closed mouth. The abdomen is commonly more or less ovate or barrel-shaped, sometimes inversely conical. The cephalis of _Theocorys_ bears a single apical horn.

Subgenus 1. _Theocoronium_, Haeckel.

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

1. _Theocorys turgidula_, Haeckel.

_Eucyrtidium turgidulum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 293, Taf. vii. fig. 13.

Shell slender, ovate, with two deep strictures, very fragile and thin-walled. Length of the three joints = 2 : 5 : 7, breadth = 2 : 6 : 6. Cephalis subspherical, with a pyramidal horn of the same length. Thorax nearly spherical. Abdomen ovate, twice as broad as the constricted mouth. Pores very numerous, regular hexagonal, three to four times as broad as the bars.

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

_Habitat._--Tropical Pacific (Philippine Sea), Stations 206 and 224, surface.

2. _Theocorys veneris_, n. sp. (Pl. 69, fig. 5).

Shell inversely ovate, with two deep strictures, smooth. Length of the three joints = 2 : 5 : 6, breadth = 3 : 7 : 6. Cephalis hemispherical, with a slender conical horn of twice the length. Thorax nearly spherical. Abdomen ovate, twice as broad as the constricted mouth. Pores regular, circular, twice as broad as the bars, quincuncially disposed.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.06; breadth, _a_ 0.03, _b_ 0.07, _c_ 0.06.

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

3. _Theocorys cretica_, Haeckel.

_Eucyrtidium creticum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 291, Taf. xi. fig. 23.

Shell ovate, thin-walled, smooth, with two deep strictures. Length of the three joints = 2 : 4 : 4, breadth = 3 : 6 : 6. Cephalis hemispherical, with a conical horn of the same length. Thorax and abdomen nearly hemispherical, inflated, united by the opposite bases of the hemispheres. Constricted mouth only one-third as broad as the abdomen. Pores very small and numerous, regular, circular, of the same breadth as the bars, quincuncially disposed.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.04, _c_ 0.04; breadth, _a_ 0.03, _b_ 0.06, _c_ 0.06.

_Habitat._--Mediterranean, Crete, Corfu, surface.

{1416}4. _Theocorys ovata_, n. sp. (Pl. 69, fig. 16).

Shell quite ovate, thick-walled, smooth, without external strictures. Length of the three joints = 2 : 2 : 9. breadth = 3 : 5 : 7. Cephalis conical, with a thick conical horn of the same length. Thorax and abdomen gradually dilated towards the base, and then hemispherical, constricted. Mouth scarcely one-third as broad as the abdomen, prolonged into a short tube. Pores regular, circular, disposed in transverse rows, two to three in the cephalis, two to three in the thorax, eight to ten in the abdomen.

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

_Habitat._--Central Pacific, Stations 263 to 268, depth 2650 to 3000 fathoms.

5. _Theocorys plutonis_, n. sp. (Pl. 69, fig. 1).

Shell ovate, thick-walled, smooth, with two slight strictures. Length of the three joints = 2 : 5 : 4, breadth = 4 : 7 : 6. Cephalis hemispherical, with a conical, oblique horn of the same length. Thorax and abdomen only slightly inflated, gradually decreasing towards the wide, little constricted mouth. Pores subregular, circular, much larger in the abdomen and the lower half of the thorax than in the upper half and the cephalis.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.04; breadth, _a_ 0.04, _b_ 0.07, _c_ 0.06.

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

6. _Theocorys scolopax_, Haeckel.

_Eucyrtidium scolopax_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 72, Taf. ix. fig. 5.

Shell slender, inversely ovate, smooth. Length of the three joints = 1 : 3 : 3, breadth = 1 : 4 : 4. Cephalis subspherical, with a long, slightly curved horn, half as long as the whole shell. Thorax campanulate. Abdomen inversely ovate, twice as broad as the constricted mouth (incomplete in Ehrenberg's figure).

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

_Habitat._--Fossil in Barbados.

Subgenus 2. _Theocorythium_, Haeckel.

_Definition._--Pores of the thorax and of the abdomen of different sizes or dissimilar forms.

7. _Theocorys dianæ_, n. sp. (Pl. 69, fig. 11).

Shell almost ovate, with two deep strictures. Length of the three joints = 3 : 6 : 8, breadth = 3 : 9 : 8. Cephalis subspherical, with a slender, pyramidal horn of three times the length. Thorax {1417}conical, constricted at the base. Abdomen bottle-shaped. Pores in the thorax irregular, polygonal, in the abdomen subregular, circular, quincuncially disposed.

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

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

8. _Theocorys hyalothorax_, n. sp.

Shell slender, ovate, with two deep strictures. Length of the three joints = 6 : 9 : 8, breadth = 7 : 12 : 11. Cephalis subspherical, with numerous densely-placed circular pores, and with a pyramidal, slender horn of the same length. Thorax hemispherical, hyaline, without any pores. Abdomen ovate, twice as broad as the constricted mouth, with two to four widely distant, transverse rows of small, circular pores.

_Dimensions._--Length of the three joints, _a_ 0.024, _b 0_.036, _c_ 0.032; breadth, _a_ 0.028, _b 0_.048, _c_ 0.044.

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

9. _Theocorys bachabunda_, Haeckel.

_Thyrsocyrtis bachabunda_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xii. fig. 4.

Shell inversely ovate, with two distinct strictures. Length of the three joints = 2 : 5 : 9, breadth = 3 : 9 : 8. Cephalis subspherical, small, with a large cylindrical horn, which is half as long as the whole shell, and armed with spines at the conical apex. Thorax conical, inflated, with small, subregular, circular, quincuncial pores. Abdomen inversely ovate, with irregular, roundish, pores of larger and smaller sizes mixed, gradually lessening towards the constricted mouth.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.09; breadth, _a_ 0.03, _b_ 0.09, _c_ 0.08.

_Habitat._--Fossil in Barbados.

10. _Theocorys attenuata_, Haeckel.

_Eucyrtidium attenuatum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. xi. fig. 16.

Shell inversely ovate, with distinct collar, but indistinct lumbar stricture. Length of the three joints = 2 : 5 : 5, breadth = 2 : 7 : 6. Cephalis hemispherical, with a short, oblique, conical horn. Thorax inflated, campanulate, with small, regular, circular, quincuncial pores. Abdomen inversely conical, with irregular pores of larger and smaller sizes mixed, gradually lessening towards the truncated mouth.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.05; breadth, _a_ 0.025, _b_ 0.07, _c_ 0.06.

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

11. _Theocorys obliqua_, n. sp. (Pl. 69, fig. 10).

Shell inversely ovate, with distinct collar, but indistinct lumbar stricture. Length of the three joints = 3 : 7 : 4, breadth = 4 : 9 : 8. Cephalis hemispherical, with a stout, pyramidal, oblique {1418}horn of the same length. Thorax and abdomen together ovate, gradually lessening towards the constricted mouth, which is only half as broad. Pores irregular, roundish, in the thorax twice to four times as broad as in the abdomen. Both joints are separated by an oblique, internal, lumbar septum, which in some specimens observed was more oblique than in that figured; some specimens had a very irregular form.

_Dimensions._--Length of the three joints, _a_ 0.025 to 0.03, _b_ 0.06 to 0.07, _c_ 0.03 to 0.04; breadth, _a_ 0.04, _b_ 0.09, _c_ 0.08.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms; also fossil in Barbados.

12. _Theocorys alauda_, Haeckel.

_Eucyrtidium alauda_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 72, Taf. ix. fig. 4.

Shell nearly spindle-shaped, decreasing from the thicker middle towards both ends. Length of the three joints = 1 : 3 : 8, breadth = 1 : 4 : 5. Cephalis subspherical, with a strong, conical horn of three times the length. Thorax campanulate, with numerous regular, circular, quincuncial pores. Abdomen inversely ovate, slender, twice as broad as the truncated mouth, with irregular, roundish pores, three to four times as large as those of the thorax.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.06, _c_ 0.16; breadth, _a_ 0.03, _b_ 0.08, _c_ 0.1.

_Habitat._--Fossil in Barbados and in Tertiary rocks of Sicily.

13. _Theocorys apollinis_, n. sp. (Pl. 69, fig. 3).

Shell ovate, with two deep strictures. Length of the three joints = 2 : 3 : 5, breadth = 2 : 5 : 7. Cephalis subspherical, with a large, straight, cylindrical horn, about as long as the whole shell (in the specimen figured this is broken off). Thorax truncate, conical. Abdomen subglobose, truncate on both poles, twice as broad as the constricted mouth. Pores quincuncial, subregular, circular, twice as broad in the abdomen as in the thorax.

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

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

14. _Theocorys sphærophila_, Haeckel.

_Eucyrtidium sphærophilum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 72, Taf. viii. fig. 16.

Shell almost ovate, rough, with two slight strictures. Length of the three joints = 2 : 7 : 10, breadth = 3 : 8 : 12. Cephalis subspherical, with a strong, conical horn of the same length. Thorax nearly spherical, with subregular, circular pores of different sizes. Abdomen ovate, truncate at both poles, nearly twice as broad as the constricted mouth, with very large, subregular, hexagonal pores, four to six times as broad as the bars, in three to four transverse, and ten to twelve longitudinal rows.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.07, _c_ 0.1; breadth, _a_ 0.03, _b_ 0.08, _c_ 0.12.

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

{1419}15. _Theocorys tuberculata_, n. sp.

Shell almost ovate, tuberculate, with deep collar, but slight lumbar stricture. Length of the three joints = 2 : 5 : 12, breadth = 3 : 8 : 11. Cephalis hemispherical, with a cylindrical horn of twice the length. Thorax hemispherical, with regular, circular, double-edged, quincuncial pores, between which conical tubercles occur. Abdomen truncate, ovate, twice as broad as the constricted mouth, with regular, circular, hexagonally-framed pores, three to four times as broad as those of the thorax.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.05, _c_ 0.12; breadth, _a_ 0.03, _b_ 0.08, _c_ 0.11.

_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms; fossil in Barbados.

16. _Theocorys martis_, n. sp.

Shell slender, ovate, with two deep strictures. Length of the three joints = 3 : 6 : 18, breadth = 4 : 8 : 12. Cephalis small, hemispherical, with a very large, sword-shaped broad horn, nearly as long as the whole shell. Thorax hemispherical, honey-comb like, with regular, circular, hexagonally-framed pores. Abdomen ovate, with irregular, roundish, very large pores, four to six times as broad as the bars, and as the pores of the thorax. Constricted mouth half as broad as the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.18; breadth, _a_ 0.04, _b_ 0.08, _c_ 0.12.

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

17. _Theocorys mercurii_, n. sp.

Shell ovate, conical, with two slight strictures. Length of the three joints = 1 : 3 : 7, breadth = 2 : 4 : 7. Cephalis hemispherical, with a broad pyramidal horn of the same length. Thorax campanulate, with longitudinal series of small, regular, circular pores, separated by divergent crests. Abdomen nearly spherical, one and a half times as broad as the constricted mouth, which is prolonged into a thin, solid, cylindrical peristome. Pores of the abdomen regular, circular, hexagonally framed, three to four times as broad as the bars, and as the pores of the thorax.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.06, _c_ 0.15; breadth, _a_ 0.04, _b_ 0.09, _c_ 0.15.

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

18. _Theocorys minervæ_, n. sp. (Pl. 69, fig. 14).

Shell ovate, conical, with two deep strictures. Length of the three joints = 1 : 3 : 4, breadth = 1 : 4 : 5. Cephalis subspherical, with a large pyramidal horn as long as the thorax, and with small, circular pores. Thorax rough, with regular, quincuncial, circular pores, three to four times as large as those of the cephalis. Abdomen barrel-shaped, with irregular, roundish pores of very different sizes, six very large pores immediately beyond the lumbar stricture, and four to five rows {1420}of pores, which are twice to four times as large as those of the thorax. Mouth truncated, with thickened margin, two-thirds as broad as the abdomen.

_Dimensions._--Length of the three joints, _a_ 0.04, _b_ 0.12, _c_ 0.16; breadth, _a_ 0.04, _b_ 0.16, _c_ 0.2.

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

Genus 620. _Axocorys_,[237] Haeckel, 1881, Prodromus, p. 434.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta), with ovate abdomen, including an internal vertical axial rod, which bears three divergent radial spines or verticils of three branches, and is prolonged into an apical horn.

The genus _Axocorys_ contains only a single but very remarkable species, and may, perhaps, represent a peculiar group, which has closer relations to the #Plectoidea# than to the other Tricyrtida. The pyriform three-jointed shell has neither lateral nor terminal free appendages, but possesses a very large apical horn, and an inner prolongation of this, an axial rod, which bears some triradiate verticils of branched spines. The original ancestral forms of this remarkable genus are probably _Plagoniscus_ and _Plectaniscus_ (pp. 912 and 924).

1. _Axocorys macroceros_, n. sp. (Pl. 68, figs. 1, 1_a_).

Shell pear-shaped, with two distinct strictures. Length of the three joints = 2 : 3 : 16, breadth = 3 : 6 : 16. Cephalis hemispherical, with few small pores. From its apex arises vertically a very long three-sided prismatic horn with denticulate edges, three to four times as long as the shell. An inner thin prolongation of the horn descends vertically nearly to the mouth, and bears on its basal end three verticils of branched spines, each verticil with three divergent forked spines (fig. 1_a_). Pores regular, circular, in the subspherical abdomen three times as large as in the hemispherical thorax. The constricted mouth is scarcely broader than the thorax.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.03, _c_ 0.16; breadth _a_ 0.03, _b_ 0.06, _c_ 0.16.

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

Genus 621. _Lophocorys_,[238] Haeckel, 1881, Prodromus, p. 434.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta), with ovate abdomen, broader than the constricted mouth. Cephalis with two divergent horns, or with a bunch of horns.

{1421}The genus _Lophocorys_ differs from its ancestral form, _Theocorys_, only in the armature of the cephalis, bearing either two divergent horns, or a corona of several radial horns. In two species there are four horns on the apex, a larger vertical (occipital) horn being surrounded by three smaller, upwards divergent horns.

1. _Lophocorys astrocephala_, n. sp. (Pl. 69, fig. 9).

Shell smooth, inversely ovate, with deep collar and slight lumbar stricture. Length of the three joints = 3 : 7 : 6, breadth = 4 : 11 : 10. Cephalis subspherical, stellate, densely covered with numerous (ten to twenty or more) divergent, large, slenderly conical horns, the longest of which reach the length of the shell. Thorax campanulate, with small, regular, circular pores. Abdomen tapering towards the constricted mouth, in the upper half with the same pores, in the lower half with smaller, scarce pores, or nearly hyaline.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.07, _c_ 0.06; breadth, _a_ 0.04, _b_ 0.11, _c_ 0.1.

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

2. _Lophocorys acanthocephala_, Haeckel.

_Eucyrtidium acanthocephalum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 70, Taf. ix. fig. 8.

Shell rough, bottle-shaped, with two slight strictures. Length of the three joints = 5 : 11 : 7, breadth = 4 : 12 : 10. Cephalis conical, with a large pyramidal horn of the same length, and three smaller divergent accessory horns at the base of the three edges of the latter. Thorax campanulate, nearly as long as the tapering abdomen (which in the figure of Ehrenberg is broken off). Pores regular, circular, quincuncial.

_Dimensions._--Length of the three joints, _a_ 0.05, _b_ 0.11, _c_ 0.07; breadth, _a_ 0.04, _b_ 0.12, _c_ 0.1.

_Habitat._--Fossil in Barbados.

3. _Lophocorys bicornis_, Haeckel.

_Eucyrtidium bicorne_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 70, Taf. xi. fig. 7.

Shell smooth, almost spindle-shaped, with two slight strictures. Length of the three joints = 2 : 8 : 3, breadth = 3 : 5 : 4. Cephalis hemispherical, with two stout, pyramidal, divergent horns of twice the length. Thorax ovate, with seven to eleven transverse rows of small, regular, circular pores (often very scarce in the upper half). Abdomen with two to four transverse rows of the same pores. Mouth constricted, half as broad as the thorax.

_Dimensions._--Length of the three joints, _a_ 0.02, _b_ 0.08, _c_ 0.03; breadth, _a_ 0.03, _b_ 0.05, _c_ 0.04.

_Habitat._--Fossil in Barbados.

{1422}4. _Lophocorys quadricornis_, n. sp.

Shell rough, slenderly ovate, with two distinct strictures. Length of the three joints = 2 : 4 : 2, breadth = 2 : 4 : 3. Cephalis ovate, with four very stout, three-sided prismatic horns; the largest is as long as the thorax and vertical upon the apex, the three smaller are as long as the cephalis and diverge upwards from the base of the former. Thorax ovate, with large, irregular, roundish pores, which are three to four times as broad as the small, circular pores of the first and the third joint. Constricted mouth half as broad as the thorax.

_Dimensions._--Length of the three joints, _a_ 0.045, _b_ 0.085, _c_ 0.04; breadth, _a_ 0.035, _b_ 0.075, _c_ 0.06.

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

5. _Lophocorys bovicornis_, n. sp. (Pl. 69, fig. 12).

Shell rough, subovate, with two deep strictures. Length of the three joints = 1 : 2 : 3, breadth = 1 : 3 : 4. Cephalis subspherical, with two divergent, curved horns of different lengths. Thorax campanulate, with small, circular pores. Abdomen subspherical, truncate at both poles, twice as broad as the constricted mouth, thorny, with very large, circular pores, four to six times as broad as those of the smaller thorax.

_Dimensions._--Length of the three joints, _a_ 0.03, _b_ 0.06, _c_ 0.09; breadth, _a_ 0.04, _b_ 0.09, _c_ 0.12.

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

Genus 622. _Theocampe_,[239] n. gen.

_Definition._--#Theocorida# (vel Tricyrtida eradiata aperta) with ovate abdomen, broader than the constricted mouth. Cephalis without horn.

The genus _Theocampe_ differs from the two preceding genera in the absence of horns on the cephalis, and may, therefore be derived from _Theocorys_ by reduction of the apical horn. It bears to the latter the same relation as _Tricolocampe_ does to _Theocyrtis_.

Subgenus 1. _Theocampana_, Haeckel.

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

1. _Theocampe ehrenbergii_, Haeckel.

_Dictyomitra ehrenbergii_, Zittel, 1876, Zeitschr. d. deutsch. geol.
Gesellsch., p. 82, Taf ii. fig. 5.

Shell ovate, smooth. Length of the three joints = 2 : 3 : 13, breadth = 4 : 7 : 12. Cephalis hemispherical. Thorax truncate, conical. Abdomen inflated, nearly spherical, twice as broad as the constricted mouth. Pores of nearly equal size and form, small, regular, circular.

{1423}_Dimensions._--Length of the three joints, _a_ 0.014, _b_ 0.018, _c_ 0.076; breadth, _a_ 0.023, _b_ 0.044, _c_ 0.073.

_Habitat._--Fossil in the chalk of Northern Germany; Brunswick (Zittel).

2. _Theocampe pirum_, Haeckel.

_Eucyrtidium pirum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 72, Taf. x. fig. 14.

_Eucyrtidium excellens_, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi. p. 540, Taf. xxxiii. fig. 31.