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Pylonium sp. Benson, 1966

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Benson, 1966, p. 250-251; pl. 16, fig. 2:

Pylonium sp.

Test consisting of two complete or nearly complete systems of dimensive girdles, the second sagittal girdle not completely developed in most tests. Inner system of girdles with elliptical outline in frontal view [see Benson, 1966, text-fig. 18 under Tetrapyle octacantha group], the P2 axis being greater than the T2 axis. Second system apparently complete, latticed girdles smooth or with only a few by-spines, without traces of a third system of girdles. Test elliptical in outline, characterized by a very long second transverse girdle, the T3 axis being about one and a half times longer than the P3 axis. Gates of second girdle system open or closed, depending upon the degree of development of the second sagittal girdle, generally elliptical to kidney-shaped in outline, with one or two cylindrical beams lying in their approximate plane and joining distally with the second sagittal girdle. Pores of the latticed girdles of the second system subcircular to elliptical, equal to subequal with subregular arrangement in some areas, but generally the lattice is irregular to subregular. Surface of the girdles generally irregular, although the general outline of the girdles is elliptical.

Measurements; based on 10 specimens from stations 27, 34, 46, and 92: length of P1 axis 12-20 Ám, of P2 axis 49-65 Ám, of P3 axis 92-215 Ám, of T1 axis 10-14 Ám, of T2 axis 37-44 Ám, of T3 axis 141-295 Ám.

Remarks. This species technically belongs to the genus Pylonium Haeckel because it has two complete systems of dimensive girdles. Because it is of very rare occurrence in the Gulf, its complete range of variation was not studied. Whether or not it represents a variant form of Tetrapy1e octacantha in the Gulf could not be determined. For these reasons a new name is not proposed for this taxon.

Distribution. This species is very rare in the Gulf. It is present only in the southern half of the Gulf at stations 34, 46, 56, 60, 81, 91, and 92: therefore, it is an oceanic species.
Benson 1966











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