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Kallosphaeridium helbyi ssp. helbyi
Kallosphaeridium? helbyi ssp. helbyi
Autonym.
Originally Canningia? minor ssp. minor, subsequently Chytroeisphaeridia minor ssp. minor, thirdly (and now) Kallosphaeridium? helbyi ssp. helbyi.
Holotype: Cookson and Hughes, 1964, pl.8, fig.1
Locus typicus: Barrington, Cambridgeshire, England
Stratum typicum: Late Albian-Early Cenomanian
Original diagnosis: Cookson and Hughes, 1964, p.43: Canningia minor
Shell almost circular in outline, in well-preserved examples slightly longer than broad, opening by the removal of an apical segment along a zigzag line, the freed edge of the shell showing notches at intervals; apex with or without a short prominence, antapex usually unindented. Girdle absent; wall c. 1 Ám thick, surface scabrate.
Dimensions. Holotype 70 x 73 µm. Range 42-73 µm long, 36-73 µm broad.
Affinities:
Cookson and Hughes, 1964, p.44: Canningia minor
Of the three described species of Canngia C. minor most closely resembles the Australian Aptian species C. colliveri Cookson and Eisenack 1960. However, it can be distinguished from this species by the less frequent occurrence of an apical prominence and indented antapex, its consistently smaller size (average dimensions of 19 specimens 56 x 52 Ám), and the finer ornamentation of the shell-membrane.
In the majority of specimens the apex is partially detached and crumpled so that a more accurate ratio of length to breadth has not been possible. Plate 8, fig. 4 shows a specimen with a girdle developed; in spite of several similarities to C. minor we prefer to record this as Canngia? sp.
Autonym.
Originally Canningia? minor ssp. minor, subsequently Chytroeisphaeridia minor ssp. minor, thirdly (and now) Kallosphaeridium? helbyi ssp. helbyi.
Holotype: Cookson and Hughes, 1964, pl.8, fig.1
Locus typicus: Barrington, Cambridgeshire, England
Stratum typicum: Late Albian-Early Cenomanian
Original diagnosis: Cookson and Hughes, 1964, p.43: Canningia minor
Shell almost circular in outline, in well-preserved examples slightly longer than broad, opening by the removal of an apical segment along a zigzag line, the freed edge of the shell showing notches at intervals; apex with or without a short prominence, antapex usually unindented. Girdle absent; wall c. 1 Ám thick, surface scabrate.
Dimensions. Holotype 70 x 73 µm. Range 42-73 µm long, 36-73 µm broad.
Affinities:
Cookson and Hughes, 1964, p.44: Canningia minor
Of the three described species of Canngia C. minor most closely resembles the Australian Aptian species C. colliveri Cookson and Eisenack 1960. However, it can be distinguished from this species by the less frequent occurrence of an apical prominence and indented antapex, its consistently smaller size (average dimensions of 19 specimens 56 x 52 Ám), and the finer ornamentation of the shell-membrane.
In the majority of specimens the apex is partially detached and crumpled so that a more accurate ratio of length to breadth has not been possible. Plate 8, fig. 4 shows a specimen with a girdle developed; in spite of several similarities to C. minor we prefer to record this as Canngia? sp.