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Prunopyle tetrapila Hays, 1965

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Skeleton consists of four concentric shells, the inner three spherical, the outer prune-shaped, with a pylome at one end. Inner three shells, surface smooth, their diameters in the ratio 1:3:7. Innermost shell, pores circular 2-3 times bar width; second shell, pores circular, of uniform size, 2-3 times bar width, 6 across equatorial diameter in some specimens, bounded by raised hexagonal frames. Third shell, pores vary in size between individuals, usually large, circular, not of uniform size, 3-10 times bar width, 6-8 across equatorial diameter, but in some specimens they may be nearly the same size as pores of fourth shell. Fourth shell, surface rough, pores usually small relative to those of third shell, circular, not uniformly spaced, and varying size. Some specimens display 10-15 short spines, triangular in cross section, scattered over the surface of the fourth shell, but in most specimens shell is without spines. Diameter of innermost shell 13-16, second shell 30- 50, third shell 80-125, fourth shell (major axis) 175-225, (minor axis) 155-220, pylome 40-50, pores of first shell 4-5, pores of second shell 5-10, pores of third shell 8-20, pores of fourth shell 5-10.
Description based on 60 individuals from samples V-16-57, 760, 800 cm; V-16-59, 800 cm; V-16-66, 840 cm; V-16-132, 605 cm; V-18-69, 800 cm.
The relationship between this species and its probable relatives found in the Antarctic sediments is discussed under Prunopyle buspinigerum. This species can easily be distinguished from othe species of this genus by its large, heavy fourth shell and the absence of spines.
Distribution: Prunopyle tetrapila, although not found in Recent surface sediments on either side of the Polar Front, is a common constituent of zone , extending upward across the red clay diatomite boundary. Its upper limit varies but in a number of cores it is similar to the upper limit of Sethocorys sp., Saturnulus planetes, and Pterocanium trilobum or the top of zone X.
Hays 1965


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