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Pterocanium trilobum (Haeckel, 1861)

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Benson, 1966, p. 410-412; pl. 28, figs. 2-3:

Lychnodictyum challengeri Haeckel

?Lychnocanium campanella Ehrenberg 1872a, Akad. Berlin, Monatsb. (1872), p. 316; 1872b, Akad. Berlin, Abhandl. (1872), Pl. 8, fig. 12.
Dictyopodium challengeri Thomson, 1877, The Voyage of the Challenger-The Atlantic, vol. 1, p. 234, fig. 52.
Dictyophimus (vel Tripocyrtis) challengeri Haeckel, 1878, Das Protistenreich, p. 47, fig. 35.
Lychnodictyum chal1engeri Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 1231.

Cephahis smooth, subspherical, with small circular pores or nearly hyaline; with a long, straight to curved, nearly vertical, conical apical horn and a thin, conical vertical spine; with six small collar pores at its base. Cephalis separated from thorax by a slight stricture or change in contour. Thorax campanulate, generally narrow, with relatively large, equal, subpolygonal to subcircular pores arranged hexagonally in longitudinal rows; pores with rudimentary polygonal frames in a few specimens; surface of thorax smooth to one with a few scattered, short, thin, conical spines. Basal margin of thorax between the three feet turned inward, terminating in a continuous septal ring from which originates a rudimentary abdominal lattice in a few tests. Dorsal and primary lateral bars of the collar region extend as indistinct thoracic ribs which continue without change in contour as the outward projecting blades of the three-bladed feet. The three feet hollow and latticed proximally, solid and three-bladed in their distal one-half to one-third. The outer surface of the proximal latticed portion of each foot convex, merges with the thoracic wall without change in contour. The inner surface is flat, extends from the internal septal ring, latticed proximally; the two edges of this surface extend distally as the two lateral blades of the solid portion of the foot. The feet are of equal length and are convex outward, but their solid distal portions are either parallel or turned slightly inward.

Measurements; based on 10 specimens from stations 27, 34, 46, and 81: length of cephalis 21-27 Ám, of thorax (to septal ring) 49-76 Ám, of feet (from septal ring) 64-185 Ám; breadth of cephalis 26-31 Ám, of thorax 84-112 Ám; length of apical horn 23-53 Ám, of vertical spine 4-11 Ám; maximum breadth between feet 130-224 Ám.

Remarks. Haeckel's (1878, fig. 35) illustration of this species differs from the majority of the Gulf specimens in having a much broader thorax and in the apparent lack of hollow proximal portions of the feet. The latter may have been overlooked by Haeckel and is not always apparent in the Gulf specimens. Lychnocanium campanella Ehrenberg likewise differs from the Gulf species in a manner similar to the above. It has much smaller pores, however, and for this reason is placed in tentative synonymy only. Neither Haeckel nor Ehrenberg mention the existence of an abdomen, but in the majority of the Gulf specimens this joint is absent.

Distribution. This species is rare in the Gulf but occurs as far north as station 133. In addition to this station it is present at stations 34, 46, 60, 64, 71, 81, 91, 92, 93, 106, and 115. It is apparently an oceanic species which does not respond to upwelling.
Haeckel (1887, p. 1231) reported this species from the tropical Atlantic at "Challenger" station 338. Ehrenberg (1872a, p. 316) reported L. campanella from the Philippine Sea. This species, therefore, appears to be widespread in Recent tropical seas.
Benson 1966


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