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Hexacontium (Hexacontella) hootsi Campbell and Clark , 1944

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Shell of fair size, globose, with three concentric spheres and six paired, opposite spines crossed in three axes, these spines three-angled with rather wide, straight, triangular blades with blunted apices and broad bases, their length less than diameter of cortical shell (about 0.67); cortical and two medullary shells spherical, regularly contoured, innermost (primary) medullary shell about 0.5 diameter of outer (secondary) medullary shell, and latter about 0.34 diameter of cortical shell; surface of cortical shell with short (6.6 μ) sepaloid needles which arise at each node of subhexagonal meshwork; wall of cortical shell thick (10μ), of medullary shells very thin; supporting beams rodlike, internal extensions of six spines; pores of cortical shell subcircular to mostly subelliptical, more or less uniform in size, 14-16 across a diameter, deeply set, and fairly well spaced in thick, ridged subhexagonal meshwork with tall funnels, pores of medullary shells smaller, subcircular and with thin framework. Length of spines (perhaps tilted), 73 μ; diameter of cortical shell, 120 μ, of primary medullary shell, 22 μ, of secondary medullary shell, 42 μ. Hexacontium hootsi n.sp. differs from other thick-walled species in having thin spines rather than thorns, these between each angle of meshwork rather than every third one as in most of recent species.

Picture: plate 2 (5) Hexacontium (Hexacontella) hootsi n.sp. U.C.M.Pal. loc. A 3463

Note: Sanfilippo et al. (1978) place this in synonymy with Hexacontium sexaculeatum (Stöhr, 1880) but Stöhr's illustration is sketchy, and as noted by Lazarus et al. (2005) there are no type localities or type material for his species. Although Campbell and Clark's published illustration is poor, the type series material and/or type localities are still available for study, and thus I retain H. hootsi as the preferred name. - dbl, June 2011.
Campbell and Clark 1944











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