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Description

Benson, 1966, p. 251-252; pl. 16, figs. 3-4:  Octopyle stenozona Haeckel  Octopyle stenozona Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 652, P1. 9, fig. 11.   Test subquadrate in outline, with one complete system of inner dimensive girdles with elliptical outline in frontal view and with the second transverse girdle complete as well as most of the second lateral girdle; the lateral girdle has short spines or thorns, parallel to the sagittal axis extending from it in the region of the poles of the principal axis, suggestive of a rudimentary second sagittal girdle; however, no specimens from the Gulf were observed with this girdle. Second transverse and lateral girdles very narrow, with large unequal pores separated by heavy intervening bars; surface of both girdles with short, stout spines or thorns, unbranched distally. Test typically with a pair of heavy, cylindrical beams, oppositely placed, coaxial with the principal axis of the test, each arising from the surface of the innermost ellipsoidal shell and joining with the second lateral girdle distally; the presence of the beams gives the test the appearance of having eight subcircular gates, four on each side of the test, whereas there are only four true gates, two each on the dorsal and ventral surfaces of the test.   Measurements; based on 8 specimens from stations 27, 34, 46, and 71 [see Benson, 1966, text-fig. 18 under Tetrapyle octacantha group]: length of P1 axis 15-18 µm, of P2 axis 43-52 µm, of P3 axis 123-191 µm, of T1 axis 11-14 µm, of T2 axis 34-41 µm, of T3 axis 119-154 µm.   Remarks. Although rare in the Gulf this species is easily distinguished from Tetrapyle octacantha by its very narrow second transverse and lateral girdles, very short sagittal axis relative to the principal and transverse axes, its generally quadrangular outline, and by the presence of the two heavy polar beams which occupy the principal axis and give the test the appearance of having eight gates instead of four. Haeckel (1887, p. 652) misinterpreted the polar beams as each representing a sagittal septum, but his illustration shows that they are beams (op. cit., P1. 9, fig. 11).   Distribution. This species is very rare in the Gulf. It is present only in the southern half of the Gulf at stations 27, 34, 46, 56, 71, 81, 91, and 106. It is, therefore, an oceanic species.  Haeckel reported Octopyle stenozona from the tropical Atlantic at "Challenger" station 338. It has not been reported from high latitudes and is apparently confined to tropical regions.

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