1. Cenolarcus primordialis, n. sp. (Pl. 50, figs. 7, 7a, 7b).
Network of the shell regular, with circular, hexagonally framed pores, twice as broad as the elevated bars; about ten pores on the half meridian, eight on the half equator. Surface a little rough. Proportion of the three dimensive axes = 2 : 2.5 : 3.
Dimensions.—Principal axis (or length) 0.12, transverse axis (or breadth) 0.1, sagittal axis (or thickness) 0.08; pores 0.01, bars 0.005.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
2. Cenolarcus dimensivus, n. sp.
Network of the shell regular, with circular pores (without hexagonal frames), three times as broad as the thin bars; about twelve pores on the half meridian, nine on the half equator. Surface thorny. Proportion of the three dimensive axes = 3 : 4 : 5.
Dimensions.—Principal axis 0.15, transverse axis 0.12, sagittal axis 0.09; pores 0.012, bars 0.004.
Habitat.—North Pacific, Station 244, surface.
3. Cenolarcus triaxonius, n. sp.
Network of the shell regular, with circular, hexagonally framed pores, four times as broad as the thin bars; about twelve pores on the half meridian, nine on the equator. Surface smooth. From the inner surface of the shell arise six very thin radial beams, opposite in pairs in the three dimensive axes; all six beams end freely in a little knob, at an equal distance from the centre; therefore this remarkable species seems to have lost a medullary shell (descending from Coccolarcus or Larnacilla?). Proportion of the three dimensive axes = 2 : 2.5 : 3.
Dimensions.—Principal axis 0.13, transverse axis 0.11, sagittal axis 0.09; pores 0.012, bars 0.03.
Habitat.—Tropical Atlantic, Station 338, depth 1990 fathoms.
4. Cenolarcus lentellipticus, n. sp.
Network of the shell regular, with circular pores of the same breadth as the thick bars; about eighteen pores on the half meridian, fourteen on the half equator. Surface smooth. Proportion of the three dimensive axes = 2 : 3 : 4.
Dimensions.—Principal axis 0.16, transverse axis 0.12, sagittal axis 0.08; pores and bars 0.004.
Habitat.—Western Tropical Pacific, Station 224, surface.
5. Cenolarcus minimus, n. sp.
Network of the shell subregular, with very small circular pores of the same breadth as the bars; only four pores on the half meridian, three on the half equator. Surface smooth. Proportion of the three dimensive axes = 3 : 4 : 5.
Dimensions.—Principal axis 0.05, transverse 0.04, sagittal axis 0.03; pores and bars 0.006.
Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.
Definition.—Larcarida with a simple, lentelliptical latticed shell, without a medullary shell; surface covered with radial spines.
The genus Larcarium differs from Cenolarcus only in the possession of radial spines on the surface of the simple fenestrated lentelliptical shell. These spines are commonly disposed symmetrically, opposite in pairs, either on the poles of the three dimensive axes, or on the poles of certain diagonal axes. Larcarium differs from the similar genera Larcidium, Larnacidium, and Larnacantha by the absence of any medullary shell.
1. Larcarium amphistylum, n. sp.
Shell thorny, with two large conical spines, opposite on both poles of the principal axis, somewhat longer than it. Network of the shell regular, with circular, hexagonally framed pores, twice as broad as the bars; about twelve pores on the half meridian, ten on the half equator. Proportion of the three dimensive axes = 3 : 4 : 5.
Dimensions.—Principal axis (or length) 0.15, transverse axis (or breadth) 0.12, sagittal axis (or thickness) 0.09; pores 0.01, bars 0.005.
Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.
2. Larcarium staurostylum, n. sp.
Shell smooth, with four short three-sided pyramidal spines of equal length, opposite in pairs on the poles of the principal and lateral axes. Network of the shell regular, with circular pores of the same breadth as the bars; about eight pores on the half meridian, six on the half equator. Proportion of the three dimensive axes = 2 : 2.5 : 3.
Dimensions.—Length of the shell 0.12, breadth 0.1, thickness 0.08; pores and bars 0.006.
Habitat.—South Pacific, Station 300, depth 1375 fathoms.
3. Larcarium hexastylum, n. sp.
Shell smooth, with six short conical spines of equal length (= the shortest axis of the shell), opposite in pairs on the poles of the three dimensive axes. Network of the shell subregular, with circular pores three times as broad as the bars; about eleven pores on the half meridian, nine on the half equator. Proportion of the three dimensive axes = 3 : 4 : 5.
Dimensions.—Length of the shell 0.1, breadth 0.08, thickness 0.06, pores 0.006; bars 0.002.
Habitat.—North Pacific, Station 244, surface.
4. Larcarium axostylum, n. sp.
Shell thorny, with six strong conical radial spines, opposite in pairs on the poles of the three dimensive axes. All three pairs are of different sizes, the length of each spine corresponding nearly to the size of the shell-axis, of which it is the prolongation. Network of the shell subregular, with circular pores twice as broad as the bars; ten on the half meridian, eight on the half equator. Proportion of the three dimensive axes = 2 : 3 : 4.
Dimensions.—Length of the shell 0.12, breadth 0.09, thickness 0.06; pores 0.01, bars 0.005.
Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.
5. Larcarium octostylum, n. sp.
Shell thorny, with eight thin cylindrical radial spines, opposite in pairs in two crossed diagonal planes. Network of the shell irregular, with roundish pores, twice to four times as broad as the bars; nine to eleven on the half meridian, five to seven on the half equator. Proportion of the three dimensive axes = 3 : 4 : 5.
Dimensions.—Length of the shell 0.11, breadth 0.09, thickness 0.07; pores 0.006 to 0.012, bars 0.003.
Habitat.—Pacific, central area, Station 267, surface.
6. Larcarium polystylum, n. sp.
Shell thorny, with numerous (twenty to thirty) stronger conical radial spines, about as long as the shortest axis of the shell. Network of the shell irregular, with roundish pores, twice to four times as broad as the bars; seven to eight on the half meridian, five to six on the half equator. Proportion of the three dimensive axes = 1 : 2 : 3.
Dimensions.—Length of the shell 0.09, breadth 0.06, thickness 0.03; pores 0.006 to 0.012, bars 0.003.
Habitat.—South Atlantic, Station 323, surface.
7. Larcarium chætostylum, n. sp.
Shell bristly, with very numerous (sixty to eighty or more) very thin, bristle-like, radial spines, somewhat longer than the longest axis of the shell. Network irregular, with very small roundish pores, about the same size as the bars; sixteen to eighteen on the half meridian, thirteen to fifteen on the half equator. Proportion of the three dimensive axes = 1 : 1.5 : 2.
Dimensions.—Length of the shell (without spines) 0.13, breadth 0.1, thickness 0.07; pores and bars 0.004 to 0.006.
Habitat.—Pacific, central area, Station 273, surface.
Definition.—Larcarida with encased lentelliptical shell, composed of two or more concentric lentelliptical latticed shells, which are united by radial beams (at least one inner medullary shell and one outer cortical shell).
Definition.—Larcarida with two concentric latticed shells, an outer lentelliptical cortical shell, and an inner (spherical or lentelliptical) medullary shell, both connected by radial beams. Surface without radial spines.
The genus Coccolarcus differs from Cenolarcus by the possession of an internal medullary shell. This is quite simple, either spherical or lentelliptical, and connected with the outer cortical shell by a number of radial beams. In the similar Larnacilla this connection is effected by four internal latticed lamellæ (the half lateral wings of the transverse girdle); therefore we find here four internal gates (on the poles of the principal axis), absent in Coccolarcus.
1. Coccolarcus lentellipsis, n. sp.
Cortical shell with smooth surface and regular network; pores circular, twice as broad as the bars; about thirteen on the half meridian, eleven on the half equator. Proportion of the three dimensive axes = 3 : 4 : 5. Medullary shell spherical, half as broad as the transverse radius.
Dimensions.—Principal axis (or length) of the cortical shell 0.15, transverse axis (or breadth) 0.12, sagittal axis (or thickness) 0.09; pores 0.01, bars 0.005; diameter of the medullary shell 0.03.
Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.
2. Coccolarcus platellipsis, n. sp.
Cortical shell with thorny surface and irregular network; pores roundish, twice to three times as broad as the bars; sixteen to eighteen on the half meridian, ten to twelve on the half equator. Proportion of the three dimensive axes = 1 : 2 : 3. Medullary shell lentelliptical, one-third as large as the cortical shell.
Dimensions.—Length of the cortical shell 0.17, breadth 0.11, thickness 0.06; pores 0.008 to 0.012, bars 0.004; medullary shell 0.03 to 0.06.
Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.
Definition.—Larcarida with two concentric latticed shells, an outer lentelliptical cortical shell, and an inner (spherical or lentelliptical) medullary shell, both connected by radial beams. Surface covered with radial spines.
The genus Larcidium differs from the foregoing Coccolarcus only in the possession of radial spines, and bears to it the same relation that Larcarium does to Cenolarcus. The spines are commonly symmetrically disposed, opposite in pairs in the dimensive axes, sometimes also in diagonal axes.
1. Larcidium dissacanthum, n. sp.
Cortical shell with thorny surface and regular network; pores circular, hexagonally framed, three times as broad as the bars; about thirteen on the half meridian, eleven on the half equator. Proportion of the three dimensive axes = 2 : 3 : 5. Medullary shell spherical, one-fourth as broad as the cortical, connected with it by two thin beams, lying in the principal axis, and prolonged on its poles into two strong conical spines, somewhat longer than the greatest axis.
Dimensions.—Length of the cortical shell (or principal axis) 0.15, breadth 0.09, thickness 0.07; pores 0.015, bars 0.005; medullary shell 0.025.
Habitat.—North Pacific, Station 253, depth 3125 fathoms.
2. Larcidium hexacanthum, n. sp.
Cortical shell with smooth surface and regular network; pores circular, twice as broad as the bars; about eleven on the half meridian, nine on the half equator. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell spherical, one-third as broad as the cortical. On the surface six strong, three-sided pyramidal spines, all about as long as the breadth of the cortical shell.
Dimensions.—Length of the cortical shell 0.12, breadth 0.1, thickness 0.08; pores 0.01, bars 0.005; medullary shell 0.035.
Habitat.—Pacific, central area. Station 266, surface.
3. Larcidium axacanthum, n. sp.
Cortical shell with rough surface and irregular network; pores roundish, twice to four times as broad as the bars; about fifteen to nineteen on the half meridian, twelve to fourteen on the half equator. Proportion of the three axes = 2 : 3 : 4. Medullary shell lentelliptical, of the same form and structure as the cortical, but only one-third as large, connected with it by six thin radial beams, lying in pairs in the three dimensive axes; on the outside they are prolonged into six strong conical radial spines, which are in pairs of different size (as in Larcarium axostylum); the length of each spine nearly equals the axis of the cortical shell, of which it is the prolongation.
Dimensions.—Length of the cortical shell (and the principal spines) 0.18, breadth of it (and length of the lateral spines) 0.135, thickness of it (and length of the sagittal spines) 0.09; pores 0.005 to 0.013, bars 0.003.
Habitat.—Pacific, central area, Station 271, surface.
4. Larcidium octacanthum, n. sp.
Cortical shell thorny, with irregular network; pores roundish, once to four times as broad as the bars; about thirteen to fifteen on the half meridian, eleven to thirteen on the half equator. Proportion of the three axes = 1 : 2.5 : 4. Medullary shell lentelliptical, one-fifth as large as the cortical, connected with it by eight radial beams, which are situated in two crossed diagonal planes (opposite in pairs), and are prolonged on the surface into eight long and thin cylindrical radial spines similar to Tetrapyle octacantha.
Dimensions.—Length of the cortical shell 0.16, breadth 0.11, thickness 0.045; pores 0.003 to 0.012, bars 0.003; medullary shell 0.02 to 0.03.
Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.
5. Larcidium dodecanthum, n. sp. (Pl. 50, figs. 8, 8a).
Cortical shell rough, with irregular network; pores roundish, twice to four times as broad as the bars; about twelve to fourteen on the half meridian, eight to ten on the half equator. Proportion of the three axes = 2 : 3 : 4. Medullary shell lentelliptical, one-third as large as the cortical, connected with it by twelve thin radial beams, which are prolonged outside into twelve strong conical radial spines, about half as long as the breadth of the shell.
Dimensions.—Length of the cortical shell 0.14, breadth 0.1, thickness 0.07; pores 0.008 to 0.015, bars 0.004; medullary shell 0.04 to 0.05.
Habitat.—South Pacific, Station 288, surface.
6. Larcidium polyacanthum, n. sp.
Cortical shell spiny, with irregular network; pores roundish, once to twice as broad as the bars; about ten to twelve on the half meridian, six to eight on the half equator. Proportion of the three axes = 1 : 2 : 3. Medullary shell lentelliptical, half as large as the cortical shell, connected with it by numerous (twenty to twenty-five) radial beams, which are prolonged outside into three-sided pyramidal spines, about as long as the breadth of the shell.
Dimensions.—Length of the cortical shell 0.18, breadth 0.12, thickness 0.06; pores 0.01 to 0.015, bars 0.008; medullary shell 0.03 to 0.09.
Habitat.—North Pacific, Station 244, depth 2900 fathoms.
Definition.—Larcarida with spongy lentelliptical shell (with or without enclosed medullary shell).
Definition.—Larcarida with lentelliptical spongy shell, containing a central cavity of the same form, without medullary shell (without radial spines).
The genus Spongolarcus differs from Cenolarcus (its probable ancestral form) only in the development of spongy framework forming the wall of the hollow lentelliptical shell. It corresponds, therefore, to Plegmosphæra among the Sphæroidea, and to Spongellipsis among the Prunoidea. From these two similar spongy Sphærellaria it differs in its characteristic lentelliptical form, with three dimensive axes of unequal length.
1. Spongolarcus lentellipsis, n. sp.
Spongy network of the shell very loose, its meshes fifteen to twenty times as broad as the bars. Surface of the shell nearly smooth; diameter of its internal cavity twice as large as the thickness of its wall. Proportion of the three dimensive axes = 2 : 3 : 4.
Dimensions.—Length 0.16, breadth 0.12, height 0.08; thickness of the spongy wall 0.05.
Habitat.—Pacific, central area, Station 274, surface.
2. Spongolarcus triaxonius, n. sp.
Spongy network of the shell rather loose, its meshes twelve to sixteen times as broad as the bars. Surface of the shell rough; diameter of its internal cavity about eight times as large as the thickness of its wall. Proportion of the three dimensive axes = 2 : 2.5 : 3.
Dimensions.—Length 0.25, breadth 0.2, height 0.16; thickness of the spongy wall 0.025.
Habitat.—North Pacific, Station 253, surface.
3. Spongolarcus dimensivus, n. sp.
Spongy network of the shell dense, its meshes four to eight times as broad as the bars. Surface of the shell thorny; diameter of its internal cavity about fifteen times as large as the thickness of its wall. Proportion of the three dimensive axes = 3 : 4 : 5.
Dimensions.—Length 0.2, breadth 0.16, height 0.12; thickness of the spongy wall 0.01.
Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.
4. Spongolarcus amphicentria, Haeckel.
? Amphicentria salpa, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 296; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. ii. fig. 18.
? Spongurus salpa, Haeckel, 1862, Monogr. d. Radiol., p. 466.
Spongy network of the shell compact, its meshes about the same breadth as the bars. Surface of the shell spiny, with some larger spines around the poles of the axis; diameter of the internal cavity about six times as large as the thickness of its wall. Proportion of the three dimensive axes = 1 : 2 : 3. (Perhaps this Spongolarcus is identical with Amphicentria salpa, very imperfectly described and figured by Ehrenberg, loc. cit.?)
Dimensions.—Length 0.14, breadth 0.09, height 0.05; thickness of the spongy wall 0.015.
Habitat.—North Atlantic; off Greenland, 1000 fathoms, Ehrenberg; Station 64, depth (2700) fathoms.
Definition.—Larcarida with lentelliptical spongy shell, composed of compact spongy framework, without central cavity and medullary shell (without radial spines).
The genus Stypolarcus differs from Spongolarcus in the absence of any central cavity. This is quite filled up by spongy framework, which forms the whole mass of the lentelliptical body. Stypolarcus bears therefore the same relation to Spongolarcus that Styptosphæra does to Plegmosphæra.
1. Stypolarcus spongiosus, n. sp.
Lentelliptical shell composed in the whole mass of loose, spongy framework of similar texture, with irregular meshes, about ten to twenty times as broad as the thin bars. Surface rough, without radial spines. Proportion of the three axes = 3 : 4 : 5.
Dimensions.—Length 0.2, breadth 0.16, height 0.12.
Habitat.—Antarctic Ocean, Station 157, depth 1950 fathoms.
Definition.—Larcoidea with a regular, completely latticed, lentelliptical cortical shell, without open gates and annular constrictions; either this cortical shell or the enclosed medullary shell is trizonal, composed of three elliptical, latticed, dimensive girdles of different sizes, perpendicular one to another.
The family Larnacida immediately follows the Larcarida as the next simple group of all Larcoidea; some genera of both groups (such as Larnacalpis and Coccolarcus, or Larnacantha and Larcidium) may easily be confounded from their being so much alike. In both the lentelliptical shell is composed of two concentric shells, an inner (medullary) and an outer (cortical) shell. But the connection between these shells and the construction of the inner shell is quite different in the two groups. Whilst in the Larcarida the medullary shell is connected with the cortical shell simply by radial beams, here in the Larnacida this connection is effected by two latticed lamellæ, which are the lateral wings of a transverse girdle. Therefore we encounter here for the first time that peculiar mode of growth which characterises the greater part of the Larcoidea, but particularly the Pylonida. But whilst in the Pylonida between the three crossed lattice-girdles, remain four open gates, here in the Larnacida the gates become closed by lattice-work; the lentelliptical cortical shell becomes perfect.
The most simple genus of Larnacida, and no doubt the common ancestral form of this whole family, is Larnacilla (Pl. 50, figs. 1, 1a, 1b). The most important shell of this typical genus is composed of a simple lentelliptical medullary shell and of three elliptical latticed girdles surrounding it, perpendicular one to another. These three "dimensive girdles" lie in the perimeter of the three dimensive planes, the minor (and first) in the equatorial plane, the second (and major) in the lateral plane, the third (and intermediate) in the sagittal plane. Therefore we have before us the same "trizonal shell" as in the important genus Trizonium among the Pylonida. But whilst in Trizonium, as in all Pylonida, the four gates between the girdles remain open, here in Larnacilla they become perfectly closed by lattice-work.
The formation of the typical "Larnacilla-shell" begins with a simple, spherical or lentelliptical lattice-shell, from both sides of which arise two latticed "lateral wings" opposite on the poles of the transverse axis. These two wings are comparable to the lateral chambers of Tholartus (among the Tholonida), but differ by two large openings. Each wing is a short cylindrical tube with latticed wall, open at both ends; the axis of the tube (going through the centre of the open ends) is parallel to the principal axis of the whole shell (and of the central chamber). Therefore both wings form together a transverse ring, the middle of which encloses the central chamber. The distal parts of both wings grow towards the poles of the principal axis; if they became united here, the second (lateral) girdle would be complete. Between it and the first girdle four open gates remain ("Tetrapyle"); but these become overgrown by the third or sagittal girdle, and at last the gates between this and the two other girdles become closed by lattice-work. This perfect fenestration of the trizonal cortical shell, and the complete closing of the gates between the girdles by network, is the only difference between Trizonium and Larnacilla.
In Larnacilla and in the nearly allied Larnacidium (only differing by radial spines on the surface) the "trizonal shell" is an external or "cortical shell," enclosing the central capsule, the interior of which only contains the simple central chamber and the jointed proximal parts of both lateral wings. In the other genera of Larnacida (by proceeding growth) this trizonal Larnacilla-shell becomes enclosed by the growing central capsule and is now only a "medullary shell," whilst on the outside of the central capsule in the same manner is developed an outer cortical shell (Larnacalpis, Larnacantha); and perhaps the same process may be repeated. But sometimes also this cortical shell becomes doubled by a simple envelop of network (Larnacoma). In the Larnacospongida the cortical shell is composed of a spongy framework (corresponding to the Spongolarcida in the foregoing family).
The lattice-work of the Larnacida is commonly irregular (as in most other Larcoidea), and its pores have little signification for the different species. On the outer surface often arise radial spines, symmetrically disposed either in dimensive planes or in diagonal planes.
The central capsule is constantly a true lentellipsis or a "triaxial ellipsoid," characterised by three halving, elliptical dimensive planes, perpendicular one to another. It bears a different relation to the skeleton in the two subfamilies of Larnacida. In the first subfamily, the Larnacillida (Larnacilla, Larnacidium), the central capsule encloses only the simple spherical or lentelliptical central chamber ("simple medullary shell"), and is enveloped by the trizonal cortical shell. In the other subfamily, the Larnacalpida (Larnacalpis, Larnacospongus, &c.), this trizonal "Larnacilla-shell" becomes enclosed by the overgrowing central capsule, which now becomes enveloped by an external, latticed or spongy, lentelliptical "cortical shell."
|
II. Subfamily Larnacillida. Medullary shell simple, spherical or subspherical. Cortical shell lentelliptical, trizonal; between them four gates. |
brace | Shell without radial spines, | 272. Larnacilla. | ||||
| Shell with radial spines, | 273. Larnacidium. | ||||||
|
II. Subfamily Larnacalpida. Medullary shell Larnacilla-shaped, double; the inner spherical or subspherical, the outer lentelliptical and trizonal. |
brace | Cortical shell simple or double, but not spongy. | brace | Cortical shell simple. | brace | Without radial spines, | 274. Larnacalpis. |
| With radial spines, | 275. Larnacantha. | ||||||
| Cortical shell double, without radial spines, | 276. Larnacoma. | ||||||
| Cortical shell simple or double, wholly or partly spongy. | brace | Shell without radial spines, | 277. Larnacospongus. | ||||
| Shell with radial spines, | 278. Larnacostupa. | ||||||
| I. Subfamily Larnacillida. Medullary shell simple, spherical or subspherical. Cortical shell lentelliptical, trizonal; between them four gates. | ||||||||
| Shell without radial spines, | ||||||||
| 272. Larnacilla. | ||||||||
| Shell with radial spines, | ||||||||
| 273. Larnacidium. | ||||||||
| II. Subfamily Larnacalpida. Medullary shell Larnacilla-shaped, double; the inner spherical or subspherical, the outer lentelliptical and trizonal. | ||||||||
| Cortical shell simple or double, but not spongy. | ||||||||
| Cortical shell simple. | ||||||||
| Without radial spines, | ||||||||
| 274. Larnacalpis. | ||||||||
| With radial spines, | ||||||||
| 275. Larnacantha. | ||||||||
| Cortical shell double, without radial spines, | ||||||||
| 276. Larnacoma. | ||||||||
| Cortical shell simple or double, wholly or partly spongy. | ||||||||
| Shell without radial spines, | ||||||||
| 277. Larnacospongus. | ||||||||
| Shell with radial spines, | ||||||||
| 278. Larnacostupa. | ||||||||
Definition.—Larnacida with a simple, spherical or lentelliptical, medullary shell, connected by the lateral wings of a latticed transverse girdle with the simple lentelliptical trizonal cortical shell; the central capsule encloses the former and is enveloped by the latter.
Definition.—Larnacida with a simple lentelliptical cortical shell, connected by the lateral wings of a latticed transverse girdle with the simple, spherical or lentelliptical, medullary shell. Surface without radial spines.
The genus Larnacilla represents the most simple form of Larnacida, and at the same time the most important common ancestral form, from which the greater number of Larcoidea may be derived, viz., all those genera which possess the characteristic "Larnacilla-shaped medullary shell." This typical form of medullary shell may be derived from the genus Trizonium among the Pylonida by the closing of the four open gates of this genus. The free opening of these four gates becomes overgrown and closed by lattice-work, developed from the free edges of the three crossed girdles, and thus finally all three girdles are united in the form of a simple lentelliptical shell (Pl. 50, figs. 1, 1a, 1b). Seen from the sagittal poles (or from the poles of the shortest axis, fig. 1), the shell exhibits on both sides of the small spherical medullary shell the two lateral wings of the transverse girdle from the face; seen from the lateral poles (or from the poles of the transverse axis, fig. 1a), one of these wings appears in the optical section as an oblong ring, which seemingly encloses the concentric medullary shell, and on both sides is grown together with the sagittal girdle; seen from the principal poles (or from the poles of the longitudinal axis, fig. 1b), both wings exhibit their elliptical opening (at the right and left from the central medullary shell). The two concentric shells are only connected by the two lateral tube-like wings of the transverse girdle; the lateral and the sagittal girdles have no connection with the medullary shell. The latter is sometimes spherical, at other times lentelliptical.
1. Larnacilla typus, n. sp. (Pl. 50, fig. 1, 1a, 1b).
Cortical shell with smooth surface and with subregular network; pores twice as broad as the bars; about twelve pores on the half meridian, ten on the half equator. Proportion of the three dimensive axes = 2 : 3 : 4. Internal four gates (between transverse and lateral girdles) roundish-triangular, little broader than high. Medullary shell spherical, scarcely one-third as broad as the lentelliptical cortical shell.
Dimensions.—Length of the cortical shell (or principal axis) 0.13, breadth of it (or transverse axis) 0.1, height of it (or sagittal axis) 0.07; pores 0.006, bars 0.003; medullary shell (diameter) 0.03.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
2. Larnacilla prometor, n. sp.
Cortical shell with rough surface and regular network; pores three times as broad as the bars; about ten on the half meridian, eight on the half equator. Proportion of the three axes = 1 : 2 : 3. Internal four gates (between transverse and lateral girdles) kidney-shaped, twice as broad as high. Medullary shell lentelliptical, of the same form as the external cortical shell, but only one third as large.
Dimensions.—Length of the cortical shell 0.15, breadth 0.1, height 0.05, pores 0.015, bars 0.005; medullary shell 0.02 to 0.05.
Habitat.—Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms.
3. Larnacilla subglobosa, n. sp.
Cortical shell nearly spherical, with thorny surface and irregular network; pores roundish, twice to four times as broad as the bars; twelve to sixteen in the half circumference. Proportion of the three axes very little different = 1.3 : 1.4 : 1.5. Internal four gates elliptical, one and a half times as broad as high. Medullary shell spherical, one-fourth as broad as the cortical shell.
Dimensions.—Length of the cortical shell 0.15, breadth 0.14, height 0.13; pores 0.006 to 0.012, bars 0.003; medullary shell 0.035.
Habitat.—Pacific, central area. Station 266, depth 2750 fathoms.
4. Larnacilla medullaris, n. sp.
Cortical shell lentelliptical, with smooth surface and irregular network; pores roundish, very small, scarcely as broad as the bars; about eight to nine on the half meridian, six to seven on the half equator. Proportion of the three axes = 3 : 4 : 6. Internal four gates elliptical. Medullary shell spherical, scarcely one-third as broad as the cortical shell. (This small species may be only the medullary shell of some other Larcoid, the cortical shell of which is not yet formed.)
Dimensions.—Length of the cortical shell 0.06, breadth 0.04, height 0.03; pores and bars about 0.004; medullary shell 0.013.
Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.
Definition.—Larnacida with a simple lentelliptical cortical shell, connected by the lateral wings of a latticed transverse girdle with the simple, spherical or lentelliptical, medullary shell. Surface armed with radial spines.
The genus Larnacidium has the same shell-formation as the foregoing Larnacilla, and differs from it only in the possession of radial spines on the surface, which in all known species exhibit a symmetrical disposition. From the nearly allied genus Larcidium it differs in the characteristic mode of connection between the two shells, owing to the different kind of growth. In Larcidium this connection is effected only by radial beams, whereas in Larnacidium (as in all Larnacida) by two lateral latticed tubes, the wings of the primary transverse girdle.
1. Larnacidium staurobelonium, n. sp.
Cortical shell smooth, with four strong conical, radial spines in the lateral plane, opposite in pairs, two on the poles of the principal and two on the poles of the transverse axis. Pores subregular, circular, twice as broad as the bars; about twelve on the half meridian. Proportion of the three axes = 2 : 3 : 4. Medullary shell spherical, one-third as broad as the cortical shell.
Dimensions.—Length of the cortical shell 0.12, breadth 0.09, height 0.06; pores 0.008, bars 0.04; medullary shell 0.03.
Habitat.—North Pacific Station 244, depth 2900 fathoms.
2. Larnacidium hexabelonium, n. sp.
Cortical shell thorny, with six strong, three-sided pyramidal, radial spines, lying opposite in pairs on the poles of the three dimensive axes. Pores subregular, circular, three times as broad as the bars; about fourteen on the half meridian. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell spherical, one-third as broad as the cortical shell.
Dimensions.—Length of the cortical shell 0.14, breadth 0.11, height 0.08; pores 0.01, bars 0.003; medullary shell 0.04.
Habitat.—South Pacific, Station 295, depth 1500 fathoms.
3. Larnacidium polybelonium, n. sp.
Cortical shell very spiny, with numerous (twenty to thirty or more) larger thin radial spines, about as long as the shell. Pores irregular, twice to five times as broad as the bars; about sixteen on the half meridian. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell lentelliptical, half as large as the cortical shell.
Dimensions.—Length of the cortical shell 0.11, breadth 0.09, height 0.07; pores 0.004 to 0.01, bars 0.002; length of the medullary shell 0.06, breadth 0.05, height 0.04.
Habitat.—Western Tropical Pacific, Station 225. depth 4475 fathoms.
Definition.—Larnacida with a double, trizonal, Larnacilla-shaped medullary shell, enclosed in the central capsule, and enveloped by a simple or double, latticed or spongy, lentelliptical, cortical shell.