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Trisolenia megalactis megalactis Bj°rklund & Goll, 1979

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Benson, 1966, p. 123; pl. 2, fig. 5:

Disolenia cf. variabilis (Haeckel)

?Solenosphaera variabilis Haeckel, 1887, Challenger Rept., Zool., vol. 18, p.113; Riedel, 1953, Journ. of Paleo., vol. 27, p. 808, Pl. 84, fig. 8.

?Tetrasolenia quadrata Ehrenberg, 1873a, Akad. Berlin, Monatsb., (1872), pp. 320-321; 1873b, Akad. Berlin, Abhandl. (1872), Pl. 10, fig. 20.

Single latticed shell ranging from subspherical or ellipsoidal to nearly discoidal with three to four (possibly more or less) unbranched, fenestrated, cylindrical tubules located approximately in one plane. Tubules merge with shell wall proximally without sharp angle but remain constant in diameter distally; mouths of tubules smooth; pores of tubules subelliptical to subrectangular, subregularly arranged in vertical rows. Shell surface smooth; pores of shell subcircular to subelliptical to irregular in shape, subequal in size, between one and two times as broad as the bars, irregular in arrangement, 13-20 on half the circumference.

Measurements; based on three specimens from station 27: major shell diameter 78-102 Ám; length of tubules 12-25 Ám; diameter of tubules 18-34Ám.

Remarks. Because this species is very rare in the Gulf, its complete range of intraspecific variation could not be studied. It is similar to Riedel's illustration (1953, Pl. 849, fig. 8) of forms from the late Tertiary of Rotti that he tentatively identified as Solenosphaera variabilis Haeckel. Both this species and Tetrasolenia quadrata Ehrenberg have four fenestrated tubules located approximately in one plane as well as a subdiscoldal, smooth, latticed shell.

Distribution. In the Gulf of California this species is very rare and occurs only at five southern Gulf stations, 27, 34, 46, 60, and 81. It is therefore an oceanic form. Its occurrence else-where has been reported from the Indian Ocean between Zanzibar and the Comoro Islands, and from the central tropical Pacific (Riedel, 1953, p. 808). It is apparently a tropical oceanic species.

Benson 1966


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