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Amphisphaera cristata Carnevale, 1908

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Benson, 1966, p. 136-139; pl. 3, figs. 4-5:

Amphisphaera cf. uranus Haeckel

?Amphisphaera uranus Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 143.

Test consisting of two to three concentric spherical shells joined by numerous radial beams two of which are heavier, oppositely placed in one axis, and continue beyond the outer shell as prominent polar spines, one generally longer than the other although both are of nearly equal length in a few specimens. Outer or third shell generally spherical, in a few tests ellipsoidal, with smooth to thorny surface, with relatively small, equal, circular to subcircular, hexagonally arranged pores, 10-17 but generally 12-14 on half the circumference; polygonal frames present in most tests, absent in a few; thickness of shell wall variable, as thick as 18 Ám. Second shell spherical with equal pores slightly smaller than those of the outer shell, otherwise similar, 8-10 on half the circumference; joined to the third shell by 5-30 or more thin, cylindrical, radial beams which arise from its surface. First or innermost shell barely visible in most tests and absent in several, polyhedral with large polygonal pores separated by thin bars, 2-3 pores on half the circumference. Polar beams arise from the surface of the first shell, are generally cylindrical and heavier than the other beams, and are oppositely placed in one axis, although in a few tests one of the beams is displaced a few degrees from the axis; in ellipsoidal tests beams are collinear with the major axis. Beams collinear with the two polar spines which are generally conical but in a few specimens are three-bladed; spines generally nearly equal in length but in a few tests one spine nearly twice the length of the other; spines of variable length and weight but are proportional to one another in each test.

Measurements; based on 30 specimens from stations 27, 34, and 46: diameter of outer (third) shell 76-166 Ám, of second shell 38-47 Ám, of first shell 16-22 Ám; length of larger polar spine 23-10 Ám, of smaller polar spine 16-80 Ám.

Remarks. This species was placed within the genus Amphisphaera Haeckel because the spines in most tests are nearly equal, and fully developed forms have three concentric shells. None of Haeckelĺs illustrated species of this genus could be identified with the Gulf species. On the basis of the size of the shells, as well as the number of regular pores on half the circumference of the outer shell, Amphisphaera uranus Haeckel (1887, p. 143) agrees fairly closely with the species from the Gulf. Identification, however, is not positive. Except for the lack of an inner shell Stylosphaera holosphaera Ehrenberg (1873 b, Pl. 8, fig. 14) is similar to the specimens from the Gulf, but identification is not positive because of Ehrenberg's poor illustration.
Stylosphaera (Sylosphaerantha) minor Clark and Campbell (1942, p. 27, Pl. 5, figs. 1, 2, 2a, 12) from the Eocene of California resembles the Gulf species but differs from it in the lack of an inner (first) shell. Without study of the type material of this species the presence of the inner shell cannot be verified. Clark and Campbell (1945 p. 11, Pl. 1, figs. 12-19) also identified the species from the Kreyenhagen formation of probable Eocene age in California. Stylosphaera fornasinii Vinassa de Regny (1900, p. 231, Pl. 1, fig. 15) from the Miocene of Italy is similar to the Gulf species but lacks the inner shell and has smaller, more numerous pores on the outer shell. The dimensions of the three shells and the number and size of the pores of the cortical shell of Amphisphaera cristata Carnevale (1908, pp. 14-15, Pl. 2, fig. 7) from the Miocene of northern Italy are similar to the Gulf species, but Carnevale's poor illustration lacks details for positive identification.
This species or species-group appears to have had a long geologic history, but the relationship of the Gulf species to the Tertiary species is not known. Specimens of the species show a large range of variation in the thickness of the outer shell wall and in the length and breadth of the polar spines, although the size and regular arrangement of the pores are relatively constant. This variability makes its identification with species illustrated in the literature difficult.

Distribution. This species is very rare in the Gulf sediments. It is present only at stations 27, 34, 46, 56, 90, 93, 133, and 184. It is present in slightly greater numbers in the southern Gulf; therefore, it should be considered an oceanic species.
A. uranus Haeckel (1887, P. 143) was reported from the western Indian Ocean. Members of this species or species-group have not been reported from high latitudes; therefore, it is probably a tropical or low latitude group.
Benson 1966


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