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Theocorythium trachelium trachelium (Ehrenberg, 1872)

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Theocyrtis trachelius (p. 1405-1406):
Shell thin-walled and very fragile, smooth. Length of the three joints = 2: 8: 7, breadth = 2: 9: 8. Cephalis subspherical, with a straight, conical horn of the same length, separated by a slender neck from the inflated, subspherical thorax. Abdomen cylindrical, with a wide open, truncate mouth. Pores subregular, hexagonal, of equal size, four to six times as broad as the thin, thread-like bars.

Dimensions: Length of the three joints, a 0.02, b 0.08, c 0.07; breadth, a 0.02, b 0.09, c 0.08.
Habitat: Tropical Pacific, many Stations (200, 224, 271, &c.), surface, and in various depths.
Haeckel 1887
Benson, 1966, p. 487-489; pl. 33, figs. 8-9:

Calocyclas amicae Haeckel

Calocyclas amicae Haeckel, 1887, Challenger Rept., Zool. , vol. 18, p. 1382, Pl.74, fig.2.
Calocyclas vestalis Haeckel, 1887, op. cit., pp. 1382-1383, Pl. 74, fig. 3.
?Eucyrtidium trachelius Ehrenberg, 1873a, Akad. Berlin, Monatsb. (1872), p . 312; 1873b, Akad . Berlin, Abhandl. (1872) , Pl. 7, fig. 8.

Cephalis nearly spherical, with rough surface, with a long, heavy, three-bladed apical horn originating eccentrically (dorsally) from its top and extending from the apical bar which is a dorsal rib in the wall of the cephalis; pores of cephalis, equal, small, subcircular to hexagonal, with hexagonal arrangement, surrounded by rudimentary polygonal frames. Cephalis separated from the campanulate thorax by a distinct necked region that in its dorsal portion has a pair of inconspicuous dorso-lateral lobes. Four collar pores present. Vertical spine, if present, is inconspicuous. Dorsal and primary lateral bars extend as indistinct ribs for a distance of 4-6 pores in the wall of the thorax; the ribs terminate in short, inconspicuous spines or thorns in several specimens. Surface of thorax smooth to rough but without spines; thoracic pores equal, hexagonal to circular, arranged hexagonally in longitudinal rows, with hexagonal frames either absent, rudimentary, or well developed. Thorax separated from a smooth to rough, cylindrical abdomen of variable length by a distinct annular constriction and continuous internal septal ring. Pores of abdomen the same as those of the thorax, although characteristically in some specimens, those of the distal, slightly inflated portion are slightly larger and less regular. Mouth of abdomen constricted, with a hyaline peristome, in several specimens with 5-10 or more triangular, tooth-like peristomal spines. A few (3-8) short, stout, three-bladed, subterminal spines more or less perpendicular to the surface of the abdomen are present in a few specimens above the level of inward curvature of the distal portion of the thorax.

Measurements: based on 11 specimens from stations 27 and 34: length of cephalis 36-42 Ám, of thorax 49-68 Ám, of abdomen 49-127 Ám; breadth of cephalis 28-34 Ám, of thorax 80-96 Ám, of abdomen 87-114 Ám; length of apical horn 17-37 Ám, of subterminal spines 6-18 Ám, of peristomal spines 6-12 Ám.

Remarks. Specimens with pores that conform to either Calocyclas amicae Haeckel or C. vestalis Haeckel are present in the Gulf and are not significantly different from one another. The only feature not observed in the Gulf species is the long peristomal spines of C. vestalis. The length of these spines as well as their presence or absence is subject to intraspecific variation, however, and should not be used as criteria for defining species. Eucyrtidium trachelius Ebrenberg has a spherical cephalis separated from a campanulate thorax by a necked region, and an incompletely developed, cylindrical abdomen; therefore, it may represent an incomplete specimen of C. amicae. Its apical horn, however, is conical and much less robust. Study of Ehrenberg's type material should determine whether or not E. trachelius is the same as C. amicae.

Distribution. This species is very rare in the Gulf. It is present only at stations 27, 34, 46, 56, 60, 71, and 92. It is predominantly an oceanic species.
This species is apparently confined to tropical to temperate seas. Calocyclas amicae was described by Haeckel from the North Pacific at "Challengerö station 253 (38-39 N). C. vestalis was reported from the central Pacific at ôChallenger" station 271. Ehrenberg (1873a, p. 312) reported Eucyrtidium trachelius from the Philippine Sea.
Benson 1966


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