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Actinomma henningsmoeni Goll and Bj°rklund, 1989

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Diagnosis: A species of Actinomma characterized by a small, thickwalled cortical shell perforated by small, densely-spaced, round pores, and the presence of 8-10 irregularly distributed internal radial beams that do not penetrate the cortical shell.
Etymology: The species is named in honor of Gunnar Henningsmoen, Professor Emeritus of the University of Oslo.
Description: Skeleton consists of three concentric, approximately spherical lattice shells joined by 8-10 round radial beams that display no obvious systematic distribution. The diameters of the inner medullary, outer medullary and cortical shells have the approximate ratio of 1:2:5. Internal structure obscured by the massive, relatively smooth cortical shell, which is densely perforated by small round pores. Fine spines project from the cortical shell of rare specimens, but the majority lack such fine spines, and the radial beams never penetrate the cortical shell as major spine processes.
Remarks: Small, more delicately constructed morphs having obvious structural affinities to A. henningsmoeni have been observed sporadically in middle and upper Miocene sediments of Site 642.
Occurrences: On the Vdring Plateau Actinomma henningsmoeni ranges from Sections 104-642D-10X-CC to -9X-CC. This species has also been observed in the Cyrtocapsella tetrapera Zone of the central equatorial Pacific (DSDP Site 77).
Size: 110-128 μm, maximum diameter of cortical shell.
Holotype: PMO 117.575; Sample 04-642D-10X-6, 25-27 cm; England Finder K13/0; PL 2, Figs. 10-11.

Goll and Bj÷rklund 1989


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