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Cleistosphaeridium armatum
Cleistosphaeridium armatum, (Deflandre, 1937, p.76-77); emend. Davey, 1969
NOW Downiesphaeridium. Originally Hystrichosphaeridium, subsequently Baltisphaeridium (Appendix A), thirdly Cleistosphaeridium, fourthly (and now) Downiesphaeridiium.
Holotype: Deflandre, 1937, pl.16 [al. pl.13], fig.6
Locus typicus: Paris Basin
Stratum typicum: Late Senonian
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Emended description:
Davey, 1969, p.153:
Diagnosis:
Shell subspherical; shell wall of moderate thickness, densely granular.
Processes numerous, fairly broad, rigid, tapering gradually distally. Proximal processes possess longitudinal basal striations; distally simple or giving rise to variable number of small spines.
Apical archaeopyle occasionally developed.
Description:
The granules are elongate (c. 0.1-0.5 µm in height) so giving the shell surface the appearance of possessing a matting of short hairs. This ornamentation, commented on by Deflandre in the original description of this species, was verified by the present author when examining the type material in Paris.
The processes are all of a similar length on any one specimen and may vary in width from 1 to 3 µm. They are hollow, always closed distally terminating either simply (the extremity may be recurved) or more commonly the distal one quarter of the processes bear a small number of stiff spines (pl. 8, fig. 2).
The opening, when observable, possesses an angular margin characteristic of an apical archaeopyle.
Dimensions:
Holotype: shell length 20 µm, width 18-20 µm, length of processes 10-15 µm.
Range of Cenomanian specimens: diameter of central body 19 (30.8)42 µm, maximum length of processes 5 (9.6) 16 µm. Number of specimens measured, 33.
Affinities:
The specimens studied strongly resemble C. armatum as described by Deflandre from Upper Cretaceous flints, one of which was of Cenomanian age. The appearance of the shell surface and form of the processes make this an easily recognizable species.
NOW Downiesphaeridium. Originally Hystrichosphaeridium, subsequently Baltisphaeridium (Appendix A), thirdly Cleistosphaeridium, fourthly (and now) Downiesphaeridiium.
Holotype: Deflandre, 1937, pl.16 [al. pl.13], fig.6
Locus typicus: Paris Basin
Stratum typicum: Late Senonian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Davey, 1969, p.153:
Diagnosis:
Shell subspherical; shell wall of moderate thickness, densely granular.
Processes numerous, fairly broad, rigid, tapering gradually distally. Proximal processes possess longitudinal basal striations; distally simple or giving rise to variable number of small spines.
Apical archaeopyle occasionally developed.
Description:
The granules are elongate (c. 0.1-0.5 µm in height) so giving the shell surface the appearance of possessing a matting of short hairs. This ornamentation, commented on by Deflandre in the original description of this species, was verified by the present author when examining the type material in Paris.
The processes are all of a similar length on any one specimen and may vary in width from 1 to 3 µm. They are hollow, always closed distally terminating either simply (the extremity may be recurved) or more commonly the distal one quarter of the processes bear a small number of stiff spines (pl. 8, fig. 2).
The opening, when observable, possesses an angular margin characteristic of an apical archaeopyle.
Dimensions:
Holotype: shell length 20 µm, width 18-20 µm, length of processes 10-15 µm.
Range of Cenomanian specimens: diameter of central body 19 (30.8)42 µm, maximum length of processes 5 (9.6) 16 µm. Number of specimens measured, 33.
Affinities:
The specimens studied strongly resemble C. armatum as described by Deflandre from Upper Cretaceous flints, one of which was of Cenomanian age. The appearance of the shell surface and form of the processes make this an easily recognizable species.