Chapter XVI: Section II: DICYRTIDA, Haeckel, 1862, Monogr. d. Radiol., pp. 280, 296 (2)

Shell flat, conical, spiny, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 8. Cephalis hemispherical, with a short conical horn of the same length. Thorax with irregular polygonal pores. Peristome with three coronals of divergent bristle-shaped spines; the first directed obliquely upwards, the second outwards, and the third nearly vertically, downwards; the bristles of the latter are much longer, about as long as the height of the shell.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.16 broad.

_Habitat._--Australia (east coast), Station 169, surface.

{1216}6. _Lampromitra schultzei_, Haeckel.

_Eucecryphalus schultzei_, Haeckel, 1862, Monogr. d. Radiol., p. 309,
Taf. v. figs. 16-19.

Shell flat, conical, smooth, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 8. Cephalis hemispherical, with a small conical horn of half the length, and very small roundish pores. Thorax with three strong, straight ribs and irregular polygonal pores, which are much larger in the middle part than in the upper or lower part. Peristome with a double coronal of short, conical, divergent spines; the superior obliquely ascending, the inferior vertically descending. (Named in honour of the late Professor Max Schultze, the illustrious histologist.)

_Dimensions._--Cephalis 0.025 diameter; thorax 0.07 long, 0.2 broad.

_Habitat._--Mediterranean, Messina, surface.

7. _Lampromitra arborescens_, n. sp, (Pl. 60, fig. 8, 8_a_).

Shell flat, pyramidal, spiny, with sharp collar stricture. Length of the two joints = 1 : 3, breadth = 2 : 10. Cephalis cap-shaped, with an oblique, slender, conical horn of twice the length, and small circular pores. Thorax with three slight almost obliterated ribs and three vaulted sides between them, with irregular roundish pores. The three ribs are distinct in the proximal, not in the distal part. Peristome with a double coronal of smaller squarish pores and numerous divergent spines; the larger spines are irregularly branched and as long as the diameter of the cephalis.

_Dimensions._--Cephalis 0.15 long, 0.03 broad; thorax 0.04 long, 0.2 broad.

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

8. _Lampromitra dendrocorona_, n. sp. (Pl. 58, fig. 9).

Shell flat, conical, with smooth surface and deep collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 10. Cephalis hemispherical, with a slender occipital horn of three times the length, and a small divergent frontal horn. Thorax with three strong prominent straight ribs and irregular polygonal meshes, increasing in size towards the mouth. Peristome with a dense coronal of numerous short conical spines and twenty-four to thirty larger arborescent spines, longer than the diameter of the cephalis.

_Dimensions._--Cephalis 0.02 long, 0.04 broad; thorax 0.08 long, 0.2 broad.

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

Genus 543. _Callimitra_,[160] Haeckel, Prodromus, 1881, p. 431.

_Definition._--#Sethopilida# (vel Dicyrtida triradiata aperta) with three vertical latticed wings, which stretch between the three divergent lateral ribs of the thorax and the vertical horn of the cephalis. No frontal horn.

{1217}The genus _Callimitra_, and the two following nearly allied genera, _Clathromitra_ and _Clathrocorys_, form together a peculiar small group, the Callimitrida, living in the Central Pacific, and differing from the other Sethopilida in some remarkable points, derived perhaps directly from the Archiscenida, _Archiscenium_ and _Pteroscenium_, by the development of thoracic network between the three cortinar feet. In the centre of the collar septum, where these feet are united, there arises a vertical free columella, prolonged over the top of the cephalis as a free horn, and this horn is connected with the three thoracic ribs by three vertical fenestrated wings.

1. _Callimitra carolotæ_, n. sp. (Pl. 63, figs. 1, 7, 8).

Cephalis campanulate, conical, with irregular, polygonal pores, and a thin bristle-shaped apical horn of the same length. Length of the two joints = 3 : 6, breadth = 2 : 6. Thorax in the upper half with irregular network, in the lower half with parallel transverse bars; in each of its three sides descend two convergent pairs of stronger, parallel, curved ribs, not confluent at the peristome. Each of the three vertical wings with eight stronger ribs, three arising from the cephalis, five from each foot. Dedicated to my dear mother Charlotte Sethe.

_Dimensions._--Cephalis 0.07 long, 0.05 broad; thorax 0.15 long, 0.15 broad.

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

2. _Callimitra annæ_, n. sp. (Pl. 63, fig. 2).

Cephalis campanulate, conical, with irregular, polygonal pores, and a thin bristle-shaped horn of the same length. Length of the two joints = 1 : 2, breadth = 1 : 3. Thorax nearly in its whole extent with parallel transverse bars, which are crossed by two convergent systems of parallel beams; in each of its three sides descend four convergent pairs of stronger, parallel, curved ribs, not confluent at the peristome. Each of the three vertical wings with six stronger ribs, three arising from the cephalis, three from each foot. Dedicated to my dear first wife Anna Sethe.

_Dimensions._--Cephalis 0.05 long, 0.05 broad; thorax 0.12 long, 0.18 broad.

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

3. _Callimitra agnesæ_, n. sp. (Pl. 63, fig. 5).

Cephalis pear-shaped, with irregular, square pores, and a slender bristle-shaped horn twice as long. Length of the two joints = 1 : 3, breadth = 1 : 5. Thorax in its whole extent with parallel transverse bars, which are crossed by two converging and crossed systems of parallel beams; in each of its three sides descend five convergent pairs of stronger, parallel, curved ribs, the two or three upper of which are crossed at the peristome. Each of the three vertical wings with five stronger ribs, three arising from the cephalis and the horn, two from each foot. Dedicated to my dear second wife Agnes Huschke.

_Dimensions._--Cephalis 0.05 long, 0.05 broad; thorax 0.15 long, 0.22 broad.

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

{1218}4. _Callimitra elisabethæ_, n. sp. (Pl. 63, fig. 6).

Cephalis nearly hemispherical, with irregular square pores, and a strong prismatic horn thrice the length. Length of the two joints = 2 : 7, breadth = 2 : 9. Thorax in the upper third with irregular network, in the lower two-thirds with parallel transverse bars which are crossed by two convergent systems of parallel beams; in each of its three sides descend three convergent pairs of stronger, parallel, curved ribs; the two ribs of the uppermost pair are united and confluent in a single odd rib in the lower half of the thorax. Each of the three vertical wings with seven stronger ribs, three arising from the cephalis and the horn, four from each foot. Dedicated to my dear elder daughter Elizabeth Haeckel.

_Dimensions._--Cephalis 0.04 long, 0.05 broad; thorax 0.15 long, 0.2 broad.

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

5. _Callimitra emmæ_, n. sp. (Pl. 63, figs. 3, 4).

Cephalis campanulate, with irregular, polygonal pores, and very thin bars (of the same shape as in the thorax) and with a thin bristle-shaped horn twice the length. Length of the three joints = 3 : 6, breadth = 2 : 9. Thorax in its whole extent with an arachnoidal network similar to that in the cephalis and the three wings, composed of very numerous parallel threads, which are crossed by two crossed diagonal systems of parallel threads. In each of the three sides of the thorax descend five convergent pairs of stronger ribs, the three upper of which are crossed and form large rhomboidal meshes. Each of the three vertical wings with ten stronger ribs, four arising from the cephalis and each horn, six from each foot. Dedicated to my dear younger daughter Emma Haeckel.

_Dimensions._--Cephalis 0.07 long, 0.06 broad; thorax 0.15 long, 0.22 broad.

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

Genus 544. _Clathromitra_,[161] Haeckel, 1881, Prodromus, p. 432.

_Definition._--#Sethopilida# (vel Dicyrtida triradiata aperta) with three vertical latticed wings, which stretch between the three divergent lateral ribs of the thorax and the vertical horn of the cephalis. The front of the latter is armed with a large frontal horn.

The genus _Clathromitra_ differs from the preceding similar _Callimitra_ in the development of a free frontal or sternal horn, a prolongation of an internal obliquely ascending rod, opposite to the caudal foot. Therefore the shell in this genus possesses five divergent free spines, two cephalic horns, and three thoracic feet. The lattice-work of the three vertical wings is not so delicate as in _Callimitra_.

{1219}1. _Clathromitra pterophormis_, n. sp. (Pl. 57, fig. 8).

Cephalis very large, hemispherical, about as long and half as broad as the three-sided pyramidal thorax; both with irregular, polygonal meshes. Apical horn three to four times as long as the frontal horn and the three basal feet. All five spines three-sided prismatic, with nearly smooth edges. Three lateral wings half as broad as the cephalis.

_Dimensions._--Cephalis 0.05 long, 0.1 broad; thorax 0.05 long, 0.15 broad.

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

2. _Clathromitra pentacantha_, n. sp.

Cephalis large, hemispherical, half as long as the three-sided pyramidal thorax; both with irregular, roundish meshes. Apical horn of about the same length as the frontal horn, and twice as long as the three basal feet. All five spines three-sided prismatic, with denticulated edges. Three lateral wings about as broad as the cephalis.

_Dimensions._--Cephalis 0.04 long, 0.08 broad; thorax 0.1 long, 0.2 broad.

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

Genus 545. _Clathrocorys_,[162] Haeckel, 1881, Prodromus, p. 432.

_Definition._--#Sethopilida# (vel Dicyrtida triradiata aperta) with three prominent lateral ribs on the thorax, alternating with three large holes (or thoracic gates). The three ribs are connected with the central apical horn of the cephalis by three vertical latticed wings.

The genus _Clathrocorys_ differs from the two preceding nearly allied genera in the incomplete fenestration of the thorax, the three perradial ribs of which are separated by three large interradial holes. It has therefore the same relation to _Callimitra_ that _Clathrocanium_ bears to _Dictyophimus_.

1. _Clathrocorys murrayi_, n. sp. (Pl. 64, fig. 8).

Cephalis pear-shaped, with irregularly square pores. From the centre of its base there arise four strong, prismatic, radial beams of nearly equal size, the vertical, straight, cephalic horn being little longer than the three divergent, somewhat curved feet. In the three meridional planes (between the horn and each foot) a few rather thick branches arise, which by communication of the ramules form the three vertical latticed wings; each wing with two large meshes, three to five meshes of medium size, and three to four parallel arachnoidal rows of small, square, distal meshes. The three walls of the flat pyramidal thorax (between every two feet) are formed in the upper part by squarish network {1220}similar to that of the cephalis, in the middle part by a single row of arches separated by thin threads, and in the lower part by a narrow band of arachnoidal network. Dedicated to Dr. John Murray.

_Dimensions._--Cephalis 0.05 long, 0.05 broad; thorax 0.04 long, 0.15 broad; apical distance of every two feet 0.15, of each foot and the horn 0.17.

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

2. _Clathrocorys teuscheri_, n. sp. (Pl. 64, fig. 10).

Cephalis pear-shaped, with irregular, square pores. From the centre of its base there arise seven prismatic, radial beams of equal strength, supporting the lattice-work of the wall; the single vertical beam is prolonged into the apical horn; six others lie in the three meridian planes (between the horn and each foot); three ascending end in the wall of the cephalis, three descending are prolonged into the three strong feet, which are longer than the horn. In each meridional plane there arise four thicker and several thinner bars, which by communication of their ramules form the three latticed wings; each wing with a single very large mesh, two meshes of medium size, and a narrow marginal band of small, square pores. The three walls of the flat pyramidal thorax are formed in the upper part by squarish network similar to that of the cephalis, in the lower part by a narrow band of the same; between them a large hole. Dedicated to Dr. Reinhold Teuscher.

_Dimensions._--Cephalis 0.05 long, 0.04 broad; thorax 0.06 long, 0.15 broad; apical distance of every two feet 0.2, of each foot and the horn 0.2.

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

3. _Clathrocorys giltschii_, n. sp. (Pl. 64, fig. 9).

Cephalis pear-shaped, with irregular, polygonal pores. From the centre of its base there arise seven prismatic, radial beams of different strength; the single vertical beam bears six lateral branches (parallel to the three ascending supporting beams), and is prolonged into the apical horn; six others lie in the three meridional planes (between the horn and each foot); three weaker ascending beams end in the wall of the cephalis, three stronger descending are prolonged into the three large diverging feet, which are twice as long as the cephalic horn. The network of the three wings and of the three-sided pyramidal thorax is about the same as in the preceding species, but much more developed; the marginal bands with the squarish network are much broader, and an arachnoidal wicker-work of very thin thread-like bars fills out the large meshes. Dedicated to Mr. Adolf Giltsch.

_Dimensions._--Cephalis 0.04 long, 0.04 broad; thorax 0.12 long, 0.2 broad; apical distance of every two feet 0.24, of each foot and the horn 0.2.

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

Genus 546. _Eucecryphalus_,[163] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 836.

_Definition._--#Sethopilida# (vel Dicyrtida triradiata aperta) with three free collar {1221}wings or solid spines arising from the collar stricture, and freely prominent between the horned cephalis and the flat conical thorax.

The genus _Eucecryphalus_, according to the restricted definition here given, comprises only those Sethopilida in which the three primary cortinar beams are perfectly free divergent collar wings, _i.e._, free spines arising outside the shell from the collar stricture, between the cephalis and thorax. The type of this genus (which I formerly united with other Sethopilida) remains _Eucecryphalus gegenbauri_.

Subgenus 1. _Eucyrtomphalus_, Haeckel, 1881, Prodromus, p. 431.

_Definition._--Peristome or margin of the basal mouth of the thorax smooth, without marginal spines.

1. _Eucecryphalus corocalyptra_, n. sp.

Shell flatly conical, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 6. Cephalis subspherical, with an oblique conical horn twice its length. Thorax conical, twice as broad as long, with regular hexagonal meshes and straight lateral outlines. From the collar stricture there arise three slender conical spines, about as long as the thorax, divergent downwards. Similar to _Corocalyptra agnesæ_ (Pl. 59, fig. 3), but without lumbar stricture and abdomen. Peristome or basal margin of the mouth of the thorax smooth, simple.

_Dimensions._--Cephalis 0.3 diameter; thorax 0.09 long, 0.18 broad.

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

2. _Eucecryphalus halicalyptra_, n. sp.

Shell flat, campanulate, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 10. Cephalis hemispherical, with two divergent conical horns, a major occipital and a minor frontal horn. Thorax with subregular hexagonal meshes and concave-convex lateral outlines, campanulate. From the collar stricture there arise three divergent bristle-shaped spines, nearly horizontal, about half as long as the thorax. Peristome smooth, with a marginal coronal of small square pores.

_Dimensions._--Cephalis 0.02 long, 0.04 broad; thorax 0.08 long, 0.2 broad.

_Habitat._--Central Pacific, Stations 266 to 274, surface.

Subgenus 2. _Eucecryphalium_, Haeckel.

_Definition._--Peristome or margin of the basal mouth of the thorax dentate, with a coronal of marginal spines.

{1222}3. _Eucecryphalus cuvieri_, n. sp.

Shell flatly conical, with slight collar stricture. Length of the two joints = 1 : 8, breadth = 2 : 10. Cephalis hemispherical, with an oblique pyramidal horn twice as long. Thorax with straight outlines and regular hexagonal meshes, increasing in size towards the mouth. From the collar stricture there arise three stout conical spines, half as long as the thorax, and diverging downwards. Peristome with a ring of small square pores and alternate conical divergent spines. Differs from the similar _Clathrocyclas alcmenæ_ (Pl. 59, fig. 6), mainly in the simple apical horn and the possession of the three collar fundamental spines.

_Dimensions._--Cephalis 0.02 long, 0.03 broad; thorax 0.15 long, 0.2 broad.

_Habitat._--Tropical Atlantic, Station 342, depth 1445 fathoms.

4. _Eucecryphalus mülleri_, n. sp.

Shell flatly campanulate, of nearly the same structure as and similar form to that of the preceding species. Differs from it mainly in the considerable size of the cephalic horn and the three collar spines, which are bristle-shaped and longer than the shell. Length of the two joints = 1 : 4, breadth = 2 : 8. The peristome bears a double marginal ring of divergent conical spines, the upper being directed upwards, the lower downwards.

_Dimensions._--Cephalis 0.02 long, 0.04 broad; thorax 0.08 long, 0.16 broad.

_Habitat._--North Pacific, Station 241, depth 2300 fathoms.

5. _Eucecryphalus gegenbauri_, Haeckel.

_Eucecryphalus gegenbauri_, Haeckel, 1862, Monogr. d. Radiol., p. 308,
Taf. v. figs. 12-15.

_Eucecryphalus gegenbauri_, R. Hertwig, 1879, Organism. d. Radiol., p.
76, Taf. viii. figs. 5, 5_a_, 5_b_.

Shell flatly conical, campanulate, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 8. Cephalis hemispherical, with a conical horn of the same length, and very small pores. Thorax about twice as broad as high, with large, subregular, hexagonal meshes, increasing in size downwards. In the upper half of the thorax the meshes are filled up by an extremely delicate arachnoidal network. From the collar stricture there arise three divergent bristle-shaped spines half as long as the thorax. Peristome with a double coronal of small square pores (the inner smaller and more numerous than the outer), and with a single coronal of divergent marginal spines. This cosmopolitan species is rather variable.

_Dimensions._--Cephalis 0.02 to 0.03 diameter; thorax 0.1 to 0.12 long, 0.02 to 0.25 broad.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

{1223}6. _Eucecryphalus campanella_, Haeckel.

_Pterocodon campanella_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 82, Taf. xix. fig. 2.

Shell campanulate, conical, with sharp collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 2. Cephalis hemispherical, with a short conical horn half as long, and very small pores. Thorax campanulate, as broad as high, with large roundish meshes, increasing in size downwards. From the collar stricture arise three strong, divergent, somewhat curved spines, nearly as long as the thorax. Peristome with a coronal of ten to twelve strong, conical, marginal spines, which are nearly parallel, directed downwards, a little curved, and half as long as the thorax. In the complete specimen examined by me, the apical horn, the three lateral wings and twelve terminal feet were well preserved.

_Dimensions._--Cephalis 0.02 to 0.03 diameter; thorax 0.06 to 0.07 long and broad.

_Habitat._--Fossil in Barbados.

Genus 547. _Amphiplecta_,[164] Haeckel, 1881, Prodromus, p. 424.

_Definition._--#Sethopilida# (vel Dicyrtida triradiata aperta) with three internal thoracic ribs, enveloped by the network of the thorax. Cephalis with a large apical opening, surrounded by a coronal of spines.

The genus _Amphiplecta_ (or _Amphicryphalus_) comprises some very peculiar forms of Sethopilida, probably widely remote from the other genera of this subfamily, and derived directly from the Plectanida (compare above, p. 921). The cortinar tripodium, composed of three feet divergent downwards, and one apical horn ascending upwards (in some species also a second frontal horn) is here enclosed in the cavity of a two-jointed shell, which exhibits two large openings, a smaller apical hole in the top of the cephalis, and a larger terminal mouth on the thorax. There is no trace of a sagittal ring.

1. _Amphiplecta amphistoma_, n. sp.

Cephalis subspherical, spiny, with sharp collar stricture on the base; its apical opening central, surrounded by a coronal of twelve to eighteen short spines. Length of the two joints = 7 : 8, breadth = 6 : 20. Thorax flatly conical, armed with bristle-shaped spines. Meshes of the network in both joints subregular, hexagonal, six to eight times as broad as the bars. Basal mouth bristly.

_Dimensions._--Cephalis 0.07 long, 0.06 broad; thorax 0.08 long, 0.2 broad.

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

2. _Amphiplecta acrostoma_, n. sp. (Pl. 97, fig. 10).

Cephalis subspherical, spiny, with distinct collar stricture on the base, its apical opening central, surrounded by a coronal of six to nine divergent denticulate spines. Length of the two joints = 5 : 6, {1224}breadth = 4 : 15. Thorax flatly conical, armed with denticulate spines. Meshes of both joints irregular, polygonal, twice to six times as broad as the bars. Basal mouth armed with longer, divergent, denticulate spines.

_Dimensions._--Cephalis 0.05 long, 0.04 broad; thorax 0.06 long, 0.15 broad.

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

3. _Amphiplecta callistoma_, n. sp. (Pl. 59, fig. 2).

Cephalis flat, cap-shaped, spiny, with obliterated collar stricture on the base; its apical opening excentric, oblique, surrounded by a coronal of ten to twenty bristle-shaped spines. Length of the two joints = 4 : 5, breadth = 7 : 25. Thorax flatly conical, armed with long bristle-shaped spines. Meshes of both joints irregular, hexagonal, twice to six times as broad as the bars. Basal mouth with a double irregular coronal of small square pores, and of bristle-shaped divergent spines.

_Dimensions._--Cephalis 0.04 long, 0.07 broad; thorax 0.05 long, 0.25 broad.

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

Genus 548. _Lychnocanium_,[165] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

_Definition._--#Sethopilida# (vel Dicyrtida triradiata aperta), with three solid terminal feet on the peristome. No thoracic ribs. Cephalis with a horn.

The genus _Lychnocanium_, very rich in common living and fossil forms, comprises those Sethopilida in which the thorax bears three simple terminal feet around the mouth, but no lateral ribs in its wall. It has therefore been probably derived from _Dictyophimus_ by reduction and loss of these three lateral ribs. The mouth is commonly more or less constricted. The three feet surrounding it are sometimes divergent, straight or curved, at other times parallel and vertical, straight, or curved and convergent. The central capsule exhibited in some living species three or four distinct lobes, filling up the upper half of the thorax.

Subgenus 1. _Lychnocanella_, Haeckel.

_Definition._--Feet divergent, straight or scarcely curved; their terminal distance greater than their basal distance.

1. _Lychnocanium lanterna_, n. sp. (Pl. 61, fig. 7).

Shell conical, rough, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis with a stout pyramidal horn of the same length. Thorax pear-shaped, twice as {1225}broad as the constricted mouth, with regular, circular pores of the same breadth as the bars. Three feet pyramidal, little divergent, straight, about as long as the cephalis.

_Dimensions._--Cephalis 0.03 long, 0.03 broad; thorax 0.09 long, 0.08 broad.

_Habitat._--Central Pacific, Stations 263 to 268, depth 2650 to 2900 fathoms.

2. _Lychnocanium continuum_, Ehrenberg.

_Lychnocanium continuum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 78, Taf. vii. fig. 11.

Shell smooth, with distinct collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis subspherical with a conical horn of the same length. Thorax pear-shaped, twice as broad as the constricted mouth, nearly hyaline, with a very small number of scattered minute pores. Three feet pyramidal, little divergent, straight, about as long as the thorax.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.06 broad.

_Habitat._--Fossil in Barbados.

3. _Lychnocanium pyriforme_, n. sp. (Pl. 61, fig. 11).

Shell pear-shaped, rough, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis hemispherical, with a conical horn of the same length. Thorax inflated, four times as broad as the constricted tubular mouth, with regular, circular pores. Three feet pyramidal, straight, divergent, about as long as the thorax.

_Dimensions._--Cephalis 0.02 long, 0.03 broad; thorax 0.12 long, 0.15 broad.

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

4. _Lychnocanium favosum_, n. sp. (Pl. 61, fig. 6).

Shell campanulate, rough, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 6. Cephalis hemispherical, with a rudimentary pyramidal horn of half the length. Thorax subglobular, three times as broad as the constricted mouth, with regular, circular pores, and an elevated hexagonal framework between them. Three feet cylindrical, slender, straight, divergent, twice to three times as long as the thorax.

_Dimensions._--Cephalis 0.02 long, 0.025 broad; thorax 0.1 long, 0.12 broad.

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

5. _Lychnocanium nodosum_, n. sp. (Pl. 61, fig. 14).

Shell campanulate, nodose, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subglobular, with a rudimentary conical horn of half the length. Thorax nearly hemispherical, twice as broad as the flat mouth, with regular, circular pores, and a variable {1226}number of scattered, conical, fenestrated protuberances. Three feet very large, prismatic, straight, divergent, twice as long as the thorax.

_Dimensions._--Cephalis 0.03 long, 0.04 broad; thorax 0.09 long, 0.12 broad.

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

6. _Lychnocanium carinatum_, Ehrenberg.

_Lychnocanium carinatum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 78, Taf. viii. fig. 5.

Shell campanulate, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis subglobular, with a slender horn of the same length. Thorax conical, twice as broad as the flat mouth, with fifteen to twenty prominent, longitudinal, divergent ribs, alternating with the same number of rows of pores. Three feet slender, prismatic, straight, divergent, twice as long as the thorax.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.06 broad.

_Habitat._--Fossil in Barbados.

7. _Lychnocanium ventricosum_, Ehrenberg.

_Lychnocanium ventricosum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 80, Taf. vii. fig. 12.

Shell pear-shaped, rough, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subglobular, with a stout conical horn twice the length. Thorax conical, three times as broad as the constricted mouth, with irregular, roundish pores of different sizes. Three feet stout, conical, divergent, half as long as the thorax.

_Dimensions._--Cephalis 0.02 long, 0.03 broad; thorax 0.07 long, 0.09 broad.

_Habitat._--Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms; fossil in Barbados.

8. _Lychnocanium tribulus_, Ehrenberg.

_Lychnocanium tribulus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 80, Taf. vii. fig. 1.

Shell pear-shaped, nodose, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 4. Cephalis subglobular, with a conical horn twice the length. Thorax ovate, twice as broad as the constricted mouth, with irregular, roundish pores of different sizes. Three stout feet strongly divergent, pyramidal, about as long as the thorax.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; 0.08 long, 0.08 broad.

_Habitat._--Fossil in Barbados.

Subgenus 2. _Lychnocanissa_, Haeckel.

_Definition._--Feet divergent, more or less curved; their terminal distance greater than their basal distance.

{1227}9. _Lychnocanium fortipes_, n. sp. (Pl. 61, fig. 12).

Shell inflated, rough, with distinct collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 6. Cephalis small, hemispherical, with a pyramidal horn of half the length. Thorax subglobular, truncate, twice as broad as the constricted mouth, with large, regular, circular pores and very thin bars. Three feet very stout, prismatic, twice as long as the thorax, widely divergent, curved with convexity outwards, club-shaped at the distal end, with denticulate edges.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax 0.1 long, 0.12 broad.

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

10. _Lychnocanium falciferum_, Ehrenberg.

_Lychnocanium falciferum_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig.
7; Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. fig. 4.

_Lithomelissa falcifera_, Haeckel, 1862, Monogr. d. Radiol., p. 303.

Shell inflated, rough, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis small, with a conical horn of half the length. Thorax subglobular, truncate, three times as broad as the constricted mouth, with small, regular, circular pores. Three feet widely divergent, twice as long as the thorax, curved like a crescent, with strong convexity outwards.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.06 broad.

_Habitat._--Fossil in Barbados.

11. _Lychnocanium tuberosum_, n. sp. (Pl. 61, fig. 13).

Shell conical, tuberculate, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subglobular, with a conical horn of the same length. Thorax inflated, twice as broad as the flat mouth, with small, irregular, roundish pores and scattered fenestrated tubercles. Three feet very large, angular, three times as long as the thorax, curved like a crescent, with strong convexity outwards.

_Dimensions._--Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.12 broad.

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

12. _Lychnocanium hirundo_, Ehrenberg.

_Lychnocanium hirundo_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 80, Taf. vii. fig. 8.

_Lithornithium hirundo_, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 53.

_Lithocampe hirundo_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 65.

Shell conical, tuberculate, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis hemispherical, with a conical horn of half the length. Thorax {1228}campanulate, twice as broad as the flat mouth, with longitudinal, divergent ribs, alternating with rows of small circular pores. Three feet divergent, striated, gradually lessening from a broad base, twice as long as the thorax, curved like a crescent, with convexity outwards.

_Dimensions._--Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.08 broad.

_Habitat._--Fossil in Tertiary rocks of Barbados and the Mediterranean (Sicily, Greece).

13. _Lychnocanium fenestratum_, n. sp. (Pl. 61, fig. 10).

Shell pear-shaped, rough, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subglobular, with a very large prismatic horn, which is about as long as the shell, with three denticulate, prominent, wing-like crests, which are pierced by a series of pores. Thorax ovate, three times as broad as the constricted, prominent mouth, with subregular, circular pores. Three feet arising somewhat above the mouth, prismatic, with denticulate edges, about as long as the thorax, divergent, curved, with convexity outwards.

_Dimensions._--Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.08 broad.

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

14. _Lychnocanium sigmopodium_, n. sp. (Pl. 61, fig. 15).

? _Lychnocanium tetrapodium_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 80, Taf. vii. fig. 3.

Shell campanulate, rough with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subspherical, with a slender pyramidal horn twice the length. Thorax inflated, conical, with regular circular pores and a wide open mouth of nearly the same breadth. Three feet widely divergent, twice as long as the thorax, angular, S-shaped, or curved with convexity inwards. (_Lychnocanium tetrapodium_ of Ehrenberg is perhaps a variety of this species?).

_Dimensions._--Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.09 broad.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, many stations at various depths; also fossil in Barbados and Sicily.

15. _Lychnocanium trichopus_, Ehrenberg.

_Lychnocanium trichopus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 80, Taf. vii. fig. 5.

Shell conical, smooth, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis subspherical, with a rudimentary conical horn of half the length. Thorax campanulate, with regular, circular pores and wide open mouth of nearly the same breadth. Three feet divergent, very slender, four to five times as long as the thorax, not broader than one pore, S-shaped, or curved with convexity inwards in the distal half.

_Dimensions._--Cephalis 0.02 long, 0.03 broad; thorax 0.07 long, 0.09 broad.

_Habitat._--Fossil in Barbados.

{1229}Subgenus 3. _Lychnocanoma_, Haeckel.

_Definition._--Feet parallel, vertical, straight, or little curved; divergent in the basal half, often convergent in the distal half; their terminal distance about equal to the basal distance.

16. _Lychnocanium tripodium_, Ehrenberg.

_Lychnocanium tripodium_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 80, Taf. vii. fig. 2.

Shell ovate, smooth, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 4. Cephalis subglobular, with a slender conical horn twice the length. Thorax inflated, twice as broad as the constricted mouth, with small, regular, circular pores. Three feet slender, prismatic, twice to three times as long as the thorax, nearly straight and parallel, vertical.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax 0.07 long, 0.07 broad.

_Habitat._--Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms; also fossil in Barbados.

17. _Lychnocanium cypselus_, Ehrenberg.

_Lychnocanium cypselus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 78, Taf. vii. fig. 10.

Shell slender, ovate, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subspherical, with a conical horn of the same length. Thorax ovate, truncate, three times as broad as the narrow, constricted mouth, with small, regular, circular pores. Three feet slender, somewhat shorter than the thorax, little curved, with convexity outwards, nearly parallel, vertical. (In the specimen figured by Ehrenberg, the third foot was broken off.)

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax 0.08 long, 0.06 broad.

_Habitat._--Fossil in Barbados.

18. _Lychnocanium ovatum_, n. sp.

Shell ovate, rough, without external collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 5. Cephalis conical, with a stout conical horn of the same length. Thorax ovate, four times as broad as the narrow constricted mouth, with small, regular, circular pores, separated by hexagonal frames of twice the breadth. Three feet cylindrical, half as long as the thorax, and three times as long as broad, straight, parallel, vertical.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax, 0.12 long, 0.1 broad.

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

{1230}19. _Lychnocanium crassipes_, Ehrenberg.

_Lychnocanium crassipes_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 78, Taf. vii. fig. 7.

Shell campanulate, rough, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a thin conical horn of the same length. Thorax semi-ovate, three times as broad as the narrow constricted mouth, with fifteen to twenty divergent, denticulate ribs, alternating with the same number of rows of small, regular, circular pores. Three feet very stout, as long as the thorax, cylindrical, nearly straight and parallel, vertical, at the distal end clavate, spinulate or a little forked.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.08 broad.

_Habitat._--Fossil in Barbados.

20. _Lychnocanium clavigerum_, n. sp. (Pl. 61, fig. 4).

Shell campanulate, sulcate, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis subglobular, with a spindle-shaped papillate horn twice the length. Thorax nearly spherical, truncate at both poles, three times as broad as the narrow, constricted, somewhat tubular mouth, with fifteen to twenty elevated meridional ribs, alternating with the same number of rows of circular pores. Three feet slender, cylindrical, twice as long as the thorax, in the basal half divergent, in the distal half convergent, club-shaped, with a thickened papillate end.

_Dimensions._--Cephalis 0.02 long, 0.025 broad; thorax 0.08 long, 0.01 broad.

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

21. _Lychnocanium pudicum_, n. sp. (Pl. 61, fig. 2).

Shell campanulate, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis hemispherical, hyaline (without pores), with a short and thick club-shaped, spinulate horn of the same length. Thorax subglobular, truncate at both poles, twice as broad as the constricted mouth, with small, irregular, roundish pores. Three feet somewhat shorter than the thorax, curved like a crescent, with convexity outwards; their distal ends club-shaped, spinulate, convergent towards the central axis.

_Dimensions._--Cephalis 0.02 long, 0.025 broad; thorax 0.06 long, 0.07 broad.

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

Genus 549. _Lychnodictyum_,[166] Haeckel, 1881, Prodromus, p. 432.

_Definition._--#Sethopilida# (vel Dicyrtida triradiata aperta), with three latticed terminal feet on the peristome, without thoracic ribs. Cephalis originally with a horn (sometimes lost).

{1231}The genus _Lychnodictyum_ differs from the preceding _Lychnocanium_ only in the fenestration of the three terminal feet, and bears therefore to it the same relation that the ancestral _Tripocyrtis_ does to _Dictyophimus_.

1. _Lychnodictyum challengeri_, Haeckel.

_Dictyopodium challengeri_, Wyville Thomson, 1877, Atlantic, vol. i. p.
234, fig. 52.

_Dictyophimus_ (vel _Tripocyrtis_) _challengeri_, Haeckel, 1878,
Protistenreich, p. 47, fig. 35.

Shell campanulate, smooth, with sharp collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a large, oblique, pyramidal horn thrice the length. Thorax with three inflated bosoms between the three decurrent ribs, which are prolonged into three vertical, parallel, pyramidal, in the upper half fenestrated feet, as long as the thorax. Pores regular, circular. Mouth constricted, flat, half as broad as the thorax.

_Dimensions._--Cephalis 0.03 diameter; thorax 0.08 long, 0.12 broad.

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

2. _Lychnodictyum wyvillei_, n. sp.

Shell pyramidal, smooth, with obliterated collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 5. Cephalis subspherical, with a large, straight, pyramidal horn of twice the length. Thorax nearly tetrahedral, inflated, with three rounded, decurrent ribs, which are prolonged into three widely divergent, angular, curved feet, about as long as the shell, with pyramidal fenestrated base. Pores regular, circular. Mouth constricted, flat, half as broad as the thorax.

_Dimensions._--Cephalis 0.025 diameter; thorax 0.08 long, 0.12 broad.

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

3. _Lychnodictyum scaphopodium_, n. sp. (Pl. 56, fig. 4).

Cephalis hemispherical, large, without horn, with irregular, small, roundish pores. Thorax a little larger, campanulate, with three broad, shovel-shaped, fenestrated, vertical feet, and larger, irregular pores. In the figured specimen the third (posterior) foot was broken off. In another specimen the three feet were somewhat longer and not so broad.

_Dimensions._--Cephalis 0.03 long, 0.05 broad; thorax 0.05 long, 0.06 broad.

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

4. _Lychnodictyum sethopodium_, n. sp.

Cephalis hemispherical, large, with a rudimentary conical horn, and very scarce small pores. Thorax twice as broad and long as the cephalis, campanulate, with irregular, roundish pores, and three slender, pyramidal, divergent feet twice the length, which in the upper half are fenestrated, in the lower half solid.

_Dimensions._--Cephalis 0.025 long, 0.045 broad; thorax 0.05 long, 0.09 broad.

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

{1232}Subfamily 2. SETHOPERIDA, Haeckel, 1881, Prodromus, p. 433.

_Definition._--#Tripocyrtida# with the basal mouth of the shell fenestrated (vel Dicyrtida triradiata clausa).

Genus 550. _Sethopera_,[167] Haeckel, 1881, Prodromus, p. 433.

_Definition._--#Sethoperida# (vel Dicyrtida triradiata clausa), with three divergent ribs enclosed in the latticed wall of the thorax. Cephalis with a horn.

The genus _Sethopera_ is probably the oldest form of the Sethoperida, and may therefore be regarded as the common ancestral form of this subfamily. The thorax exhibits three radial ribs, which are completely enclosed in its wall. Sethopera may be derived either from _Dictyophimus_ or from another of the Sethopilida (_Lamprodiscus, Clathrocanium_) by development of a basal lattice-plate closing the mouth. There are often wide holes or open spaces between the three radial ribs.

1. _Sethopera tricostata_, n. sp. (Pl. 97, fig. 11).

Cephalis subspherical, spinulate, with a pyramidal horn of the same length. Length of the two joints = 5 : 8, breadth = 5 : 8. Thorax also nearly spherical; in the upper half with three stout, prismatic, convex, divergent ribs, and three large ovate holes between them; in the lower half with numerous small and irregular pores, spinulate.

_Dimensions._--Cephalis 0.05 diameter; thorax 0.08 diameter.

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

2. _Sethopera oceania_, Haeckel.

_Lithopera oceania_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 297, Taf. iv. fig. 21.

Cephalis hemispherical, with a small bristle-shaped horn of half the length (broken off in Ehrenberg's figure). Length of the two joints = 3 : 4, breadth = 3 : 4. Thorax nearly spherical; in the upper half with three divergent ribs, separated by some larger, irregular pores; in the lower half with numerous small, irregular, roundish pores.

_Dimensions._--Cephalis 0.03 long, 0.03 broad; thorax 0.04 long, 0.04 broad.

_Habitat._--North Atlantic, Station 354, surface; Canary Islands and Azores.

3. _Sethopera pyrum_, Haeckel.

? _Lithopera pyrum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 297.

Cephalis hemispherical, with a small conical horn of half the length. Length of the two joints = 3 : 10, breadth = 3 : 7. Thorax pear-shaped, with rather large, regular, quincuncial pores; {1233}its upper half with three divergent ribs in the wall, half as broad as the subspherical lower half. (The three ribs probably were overlooked by Ehrenberg.)

_Dimensions._--Cephalis 0.03 long, 0.03 broad; thorax 0.1 long, 0.07 broad.

_Habitat._--North Pacific, Station 256, surface; Californian Sea, 2600 fathoms, Ehrenberg.

4. _Sethopera lagena_, Haeckel.

_Lithopera lagena_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 78, Taf. iii. fig. 4.

Cephalis pear-shaped, with a small conical horn of half the length. Length of the two joints = 3 : 8, breadth = 3 : 6. Thorax smooth, pear-shaped, with irregular roundish pores; in the wall of its upper third three divergent thin ribs (sometimes wanting); the lower half inflated. (Compare _Sethocapsa lagena_.)

_Dimensions._--Cephalis 0.03 long, 0.03 broad; thorax 0.08 long, 0.06 broad.

_Habitat._--Fossil in Barbados.

Genus 551. _Lithopera_,[168] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

_Definition._--#Sethoperida# (vel Dicyrtida triradiata clausa), with three divergent ribs enclosed in the cavity of the thorax. Cephalis with a horn.

The genus _Lithopera_ is, like the preceding _Sethopera_, one of the most simple and oldest forms of the Sethoperida, and exhibits three divergent thoracic ribs, which are prolonged neither into lateral wings nor into basal feet. But whilst in _Sethopera_ the three ribs are enclosed in the lattice-work of the shell-wall, in _Lithopera_ they lie freely in its cavity, and are overgrown by the enveloping shell-wall, being inserted on its inner face with their distal ends. _Lithopera_ may be derived directly from _Lithomelissa_, by development of lattice-work closing the shell-mouth. Therefore the lower part of the cephalis is hidden in the uppermost part of the thorax; only its upper part is free.

1. _Lithopera bacca_, Ehrenberg.

_Lithopera bacca_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin,
p. 297, Taf. viii. fig. 1.

Cephalis spherical, with small, irregular pores and a bristle-shaped spine of half the length; its lower half hidden in the thorax. Length of the two joints = 1 : 6, breadth = 1 : 5. Thorax ellipsoidal, smooth, with regular, hexagonal, small pores, and very thin, thread-like bars. From the deep collar stricture there arise three internal, divergent bars, which are inserted at the uppermost third of the thorax.

_Dimensions._--Cephalis 0.02 diameter; thorax 0.12 long, 0.1 broad.

_Habitat._--Tropical Pacific, Stations 200, 224, 266, 271, &c., surface.

{1234}2. _Lithopera bursella_, Ehrenberg.

_Lithopera bursella_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. x. fig. 4.

Shell of about the same form and structure as in the nearly allied preceding species, but smaller, of more slender form, with smaller pores and thinner bars. Length of the two joints = 1 : 5, breadth = 1 : 3. In the specimen observed by me the three internal, divergent bars of the ellipsoidal thorax (not seen by Ehrenberg) were as distinct as in the similar preceding and following species.

_Dimensions._--Cephalis 0.02 diameter; thorax 0.1 long, 0.06 broad.

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

3. _Lithopera ananassa_, n. sp. (Pl. 57, fig. 3).

Shell of about the same form and structure as in the two preceding species, but larger and more robust, and differing in the spiny surface. Length of the two joints = 1 : 5, breadth = 1 : 4. Here also the lower half of the spherical cephalis is submerged in the ellipsoidal thorax, and from the collar stricture arise three strong, internal, divergent beams. The bars of the hexagonal pores are much thicker than in the two preceding species.

_Dimensions._--Cephalis 0.03 diameter; thorax 0.16 long, 0.12 broad.

_Habitat._--Tropical Atlantic, Stations 347 to 352, surface.

4. _Lithopera globosa_, n. sp.

Cephalis spherical, very small, with two divergent conical horns of half the length; its lower half hidden in the thorax. Length of the two joints = 1 : 5, breadth = 1 : 5. Thorax spherical, with regular, circular, hexagonally-framed pores. From the collar stricture arise three radial internal beams, horizontally diverging, and inserted at the inside of the thorax.

_Dimensions._--Cephalis 0.03 diameter; thorax 0.15 diameter.

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

5. _Lithopera gutta_, Ehrenberg.

_Lithopera gutta_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin,
p. 297, Taf. viii. fig. 2.

Shell pear-shaped, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis spherical, with a conical horn of the same length; its lower half hidden in the uppermost part of the ovate thorax, and connected with its wall by three internal, cortinar beams. Pores of the thorax very irregular in form and size, partly lobed.

_Dimensions._--Cephalis 0.02 diameter; thorax 0.08 long, 0.06 broad.

_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms; Philippine Sea (depth 3300 fathoms), Ehrenberg.

{1235}Genus 552. _Micromelissa_,[169] Haeckel, 1881, Prodromus, p. 433.

_Definition._--#Sethoperida# (vel Dicyrtida triradiata clausa), with three divergent, solid, lateral wings. Cephalis with a horn.

The genus _Micromelissa_ differs from the two preceding genera in the free prominence of the three cortinar ribs, forming three solid lateral wings. Beyond these the thorax walls are convergent, and the basal mouth closed by a lattice-plate. Therefore _Micromelissa_ may have arisen from _Lithomelissa_ simply by development of this basal mouth-plate.

1. _Micromelissa bombus_, n. sp. (Pl. 57, fig. 14).

Shell smooth, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis spherical, with an oblique conical horn of the same length. Thorax subspherical, in the upper half with three conical, downwardly diverging wings, about as long as its radius. Pores very small and scarce.

_Dimensions._--Cephalis 0.02 long, 0.02 broad; thorax 0.09 long, 0.1 broad.

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

2. _Micromelissa vespa_, n. sp.

Shell smooth, with deep collar stricture. Length of the two joints = 2 : 5, breadth = 2 : 3. Cephalis spherical, with an oblique pyramidal horn twice the length. Thorax inversely ovate, in the upper half with three pyramidal wings, which are equal to its breadth, little curved and diverging downwards. Pores very small and scarce.

_Dimensions._--Cephalis 0.04 diameter; thorax 0.1 long, 0.06 broad.

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

3. _Micromelissa apis_, n. sp.

Shell rough, with deep collar stricture. Length of the two joints = 2 : 3, breadth = 2 : 4. Cephalis subspherical, with a straight conical horn of half the length, and subregular, circular, double-contoured pores, of the same breadth as the bars. Thorax little larger, subspherical, with irregular, roundish pores, twice to four times as broad as the bars. From its lower half arise three short conical wings, curved downwards, and half as long as the cephalis.

_Dimensions._--Cephalis 0.04 long, 0.04 broad; thorax 0.06 long, 0.08 broad.

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

{1236}4. _Micromelissa microptera_, Haeckel.

_Lithomelissa microptera_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig.
2; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 78, Taf. iii. fig. 13.

_Lithomelissa microptera_, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi. p. 539, Taf. xxxiii. fig. 26.

Shell smooth, with distinct collar stricture. Length of the two joints = 4 : 6, breadth = 3 : 5. Cephalis ovate, with a straight sword-shaped horn of the same length and very small pores, some larger ones above the stricture. Thorax little larger, ovate, nearly hyaline, with very few and small scattered pores. From its uppermost part arise three short conical wings, scarcely half as long as the cephalic horn, little curved and divergent downwards.

_Dimensions._--Cephalis 0.04 long, 0.03 broad; thorax 0.06 long, 0.05 broad.

_Habitat._--Fossil in Barbados.

5. _Micromelissa ventricosa_, Haeckel.

_Lithomelissa ventricosa_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 78, Taf. iii. fig. 11.

Shell rough, with slight collar stricture. Length of the two joints = 1 : 7, breadth = 1 : 5. Cephalis small, hemispherical, with a small conical horn of half the length. Thorax ovate, very large, papillate, with irregular, roundish pores. From its basal part arise three short and stout conical wings at great distances, shorter than the cephalis. (A transition-form to _Sethocapsa_.)

_Dimensions._--Cephalis 0.02 long, 0.022 broad; thorax 0.14 long, 0.11 broad.

_Habitat._--Fossil in Barbados.

Genus 553. _Peromelissa_,[170] Haeckel, 1881, Prodromus, p. 433.

_Definition._--#Sethoperida# (vel Dicyrtida triradiata clausa) with three divergent solid lateral wings. Cephalis without horn.

The genus _Peromelissa_ differs from the preceding ancestral form, _Micromelissa_, only in the absence of the cephalic horn, which is lost by reduction.

1. _Peromelissa phalacra_, n. sp. (Pl. 57, fig. 11).

Shell smooth, with two joints of nearly equal size and similar ovate form. Cephalis in the upper half hyaline, without pores; in the lower half with four remote, transverse rows of irregular, roundish pores, decreasing in size towards the hemispherical summit. Thorax with twelve transverse {1237}rows of pores, the upper six rows three to four times as large as the lower six rows. From its upper half diverge almost horizontally three angular club-shaped wings, half as long as the shell.

_Dimensions._--Cephalis 0.05 long, 0.06 broad; thorax 0.06 long, 0.05 broad.

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

2. _Peromelissa psilocrana_, n. sp.

Shell smooth, very similar to the preceding species in size and form, but differing from it in the disposition of the irregular, roundish pores, which are irregularly scattered, and in the form of the three wings, which are slender, pyramidal, diverging downwards, and about as long as the entire shell.

_Dimensions._--Cephalis 0.07 long, 0.06 broad; thorax 0.07 long, 0.06 broad.

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

3. _Peromelissa capito_, Haeckel.

_Lithomelissa capito_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 78, Taf. iii. fig. 14.

Shell rough, with two joints of nearly equal size and similar ovate form. Pores irregular, roundish, everywhere scattered. From the upper half of the thorax arise three short conical wings, which are little curved and diverge downwards (scarcely half as long as the breadth of the shell).

_Dimensions._--Cephalis 0.07 long, 0.06 broad; thorax 0.07 long, 0.06 broad.

_Habitat._--Fossil in Barbados.

4. _Peromelissa calva_, n. sp. (Pl. 57, fig. 12).

Shell rough, with two ovate joints of somewhat different sizes. Pores irregular, roundish, everywhere scattered. Thorax little larger than the cephalis; from its upper half arise three short conical wings, diverging downwardly or nearly horizontally.

_Dimensions._--Cephalis 0.06 long, 0.04 broad; thorax 0.07 long, 0.05 broad.

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

Genus 554. _Sethomelissa_,[171] Haeckel, 1881, Prodromus, p. 431.

_Definition._--#Sethoperida# (vel Dicyrtida triradiata clausa) with three divergent latticed lateral wings. Cephalis with a horn (or a bunch of horns).

The genus _Sethomelissa_ differs from the nearly allied _Micromelissa_ in the fenestration of the three lateral wings, and may be derived either from this genus by development of lattice-work connecting the three wings with the shell, or perhaps from _Clathrocanium_ by closing the mouth.

{1238}1. _Sethomelissa hymenoptera_, n. sp.

Cephalis subspherical, thorny, with a bunch of three divergent, larger apical spines. Thorax pear-shaped, with three broad, triangular, latticed wings, the superior edge of which is a horizontal, straight, and stout spine, nearly as long as the thorax. Pores irregular, roundish.

_Dimensions._--Cephalis 0.03 diameter; thorax 0.11 long, 0.08 broad.

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

Genus 555. _Tetrahedrina_,[172] Haeckel, 1881, Prodromus, p. 433.

_Definition._--#Sethoperida# (vel Dicyrtida triradiata clausa) with a three-sided pyramidal thorax, the three edges of which are prolonged into three divergent, solid, terminal feet. Cephalis with a horn.

The genus _Tetrahedrina_, and the two following nearly allied genera, are distinguished by the possession of three free, divergent, terminal feet, projecting over the latticed mouth of the thorax. _Tetrahedrina_ may be derived directly from _Dictyophimus_, by development of a horizontal latticed mouth-plate from the middle part of the feet, the lower part of which remains free. This genus, not noticed by Ehrenberg, is similar to his _Lithochytris_, and common in the Barbados deposits.

1. _Tetrahedrina pyramidalis_, n. sp.

Shell three-sided pyramidal, smooth, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 4. Cephalis hemispherical, with small, sparsely disposed pores, and a pyramidal horn of the same length. Thorax with subregular, circular pores and three sharp edges, prolonged into three divergent pyramidal feet of the same length.

_Dimensions._--Cephalis 0.03 diameter; thorax 0.12 long, 0.12 broad.

_Habitat._--Fossil in Barbados.

2. _Tetrahedrina pyriformis_, n. sp.

Shell pear-shaped, rough, with distinct collar stricture. Length of the two joints = 2 : 6, breadth = 2 : 5. Cephalis subspherical, with a conical horn of the same length. Thorax with subregular, circular pores, ovate, at the broad base with three pyramidal, widely divergent feet of the same length. (Similar to _Lychnocanium tribulus_, Ehrenberg, 1875, _loc. cit._, pl. vii. fig. 1, but with the mouth closed by a lattice-plate.)

_Dimensions._--Cephalis 0.04 diameter; thorax 0.12 long, 0.1 broad,

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

{1239}3. _Tetrahedrina quadricornis_, Haeckel.

_Lithochytris triangula_, Bury, 1862, Polycystins of Barbados, pl. xix.
figs. 4, 5, 6.

Shell pear-shaped, papillate, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 5. Cephalis subspherical, with a stout conical horn twice the length. Thorax with irregular, roundish, lobulated pores, with three conical, stout, divergent feet at the base, of the same size and form as the cephalic horn.

_Dimensions._--Cephalis 0.02 diameter; thorax 0.1 long, 0.1 broad.

_Habitat._--Fossil in Barbados.

Genus 556. _Sethochytris_,[173] Haeckel, 1881, Prodromus, p. 433.

_Definition._--#Sethoperida# (vel Dicyrtida triradiata clausa) with three terminal latticed feet or hollow, fenestrated, divergent, basal apophyses of the thorax. Cephalis with a horn.

The genus _Sethochytris_ differs from the preceding _Tetrahedrina_ in the fenestration of the three basal feet, which form direct protrusions or evaginations of the three basal corners of the pyramidal shell. It may be derived from _Sethopera_ by centrifugal growth of the basal corners.

1. _Sethochytris triconiscus_, n. sp. (Pl. 57, fig. 13).