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Siphocampe sp. (Benson, 1966)

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Benson, 1966, p. 517-520; pl. 35, fig. 9:

Siphocampium sp.

Cephalis, dorsal lobe, and six collar pores as in Siphocampium cf. polyzona. Apical spine generally absent. Thoracic ribs absent or indistinct when present. Ventral tube shorter than in S. cf. polyzona but adheres to thoracic wall. Thorax campanulate to truncate-conical, separated from a relatively long, cylindrical abdomen by a distinct stricture and septal ring. Terminal margin of abdomen generally incomplete, mouth not constricted. In one specimen abdomen subdivided by a stricture and septal ring into a proximal segment about as long as the thorax and a distal segment about 4-5 times the length of the thorax. In nearly all tests only three joints present. Surface of test smooth. Pores of cephalis small, equal, circular, about as wide as the intervening bars. Pores of the thorax and abdomen equal, subcircular to hexagonal, relatively large, separated by thin intervening bars, hexagonally arranged in transverse rows, 3-4 on the thorax, 7-15 on the abdomen.

Measurements; based on 6 specimens from stations 27, 34, and 60: maximum length of test 86-132 µm, maximum breadth (abdomen) 53-65 µm; length of cephalis 16-18 µm, of thorax 17-25 µm, of abdomen (including two joints in one test) 49-100 µm; breadth of cephalis 18-25 µm, of thorax 37-43 µm; length of apical spine 0-6 µm, of ventral tube 9-10 µm.

Remarks. This species differs from Siphocampium cf. polyzona by its smaller size, the presence of only a single abdominal segment in most tests, and by the larger, hexagonal, hexagonally arranged thoracic and abdominal pores. The presence of a ventral cephalic tube conforms to the genus Siphocampium Haeckel. Because this species is rare in the Gulf and the specimens studied are incompletely developed, the complete range of its variation could not be determined. For this reason a new name is not proposed.

Distribution. This species is very rare but nearly cosmopolitan in the Gulf. As in Siphocampium cf. polyzona, it is present at stations 191 and 192 in the northern Gulf but is absent at station 194 and all those to the north. It is also absent at stations 46, 64, 90, 95, 99, 130, 133, 151, and 184. Its absence nearshore and in the northern shelf region of the Gulf indicates its preference for offshore, more nearly oceanic waters. Its sparse distribution in the northern Gulf suggests its greater affinity for normal oceanic than for Gulf waters.
(Benson) 1966











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