. Bulletin of the British Museum (Natural History), Geology. ACRITARCHS AND CHITINOZOA 341 Dimensions. Vesicle diameter range 34-43/mi, mean 37 /mi; process length range 11-20/mi, mean 14 /im. Remarks. Superficially, the specimens resemble two species of Solisphaeridium described by Cramer & Diez (1977) from the Upper Arenig of Morocco. S. solare has a smaller vesicle and relatively long, stout processes, while S. solidispinosum is distinguished by its numerous, acu- minate, conical processes. Solisphaeridium sp. B Figs 84-85,87-89 Material. Six specimens. Occurrence. Cwm yr Abbey Member:
. Bulletin of the British Museum (Natural History), Geology. ACRITARCHS AND CHITINOZOA 341 Dimensions. Vesicle diameter range 34-43/mi, mean 37 /mi; process length range 11-20/mi, mean 14 /im. Remarks. Superficially, the specimens resemble two species of Solisphaeridium described by Cramer & Diez (1977) from the Upper Arenig of Morocco. S. solare has a smaller vesicle and relatively long, stout processes, while S. solidispinosum is distinguished by its numerous, acu- minate, conical processes. Solisphaeridium sp. B Figs 84-85,87-89 Material. Six specimens. Occurrence. Cwm yr Abbey Member: MPA 20084, MPA 20103. Description. The vesicle is subspherical and has a granulate wall. The sides of the vesicle between the process bases are convex, rarely concave. Numerous short, slender, tapering, acuminate and possibly solid processes are present. Dimensions. Vesicle diameter range 17-24/mi, mean 21 /mi; process length range 2-8 /mi, mean 5/mi. Remarks. The short processes and the nature of the ornament on the vesicle distinguish these specimens from the type and other species of Solisphaeridium. The specimens from MPA 20084 have about 15-20 processes, their lengths being more or less equal to a third of the vesicle diameter. Those from MPA 20103 differ slightly, in that they have more than 30 processes with an average length of less than a fifth of the vesicle diameter. Since relatively few specimens have been recorded and their preservation is poor, these differences are not used to separate the specimens from the two samples. The specimens bear a strong resemblance to Baltisphaeridium cinctum (Timofeev) Rauscher (in Rauscher 1973: 71; pi. 2, figs 7a-b) but have smaller vesicles. Genus STELLECHINA TUM Turner, 1984 Type species. Stellechinatum celestum (Martin 19696) Turner 1984. Stellechinatum papulessum sp. nov. Figs 90-92 Diagnosis. A species of Stellechinatum with eight to ten processes, which are wide and conical at the base but cylindrical distally. The processes,
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