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Kisselovia tenuivirgula
Kisselovia tenuivirgula (Williams and Downie, 1966) Lentin and Williams, 1976
Now Charlesdowniea. Originally Wetzeliella, subsequently Kisselovia, thirdly (and now) Charlesdowniea.
Holotype: Williams and Downie, 1966, pl.19, fig.2, 4; text-fig.49
Locus typicus: Sheppey, England
Stratum typicum: Early Eocene
Original diagnosis: Williams and Downie, 1966, p. 188: Wetzeliella (Wetzeliella) tenuivirgula
Periphragm outline pentagonal to ovoidal, with each angle produced into a well developed tapering horn--one apical, two lateral and one or two antapical. Right antapical horn always the longer. Periphragm flattened in cross section, save medially where it encloses the ovoidal capsule. Hollow, slender or branched processes arising from periphragm and arranged in simulate complexes or occurring haphazardly within complexes. Processes terminating distally in elongate, solid secae, sometimes united to secae of adjacent processes; giving rise to interconnections between processes on opposite sides of plate or remaining unconnected. Tabulation typical of genus, with three sulcal plates. Archaeopyle usually formed.
Dimensions: Periphragm, length 125--175 Ám; breadth 120--158 Ám. Capsule, length, 72-113 Ám; breadth 70-104 Ám.
Original description: Williams and Downie 1966, p. 189: Wetzeliella (Wetzeliella) tenuivirgula
W. tenuivirgula commonly has an outline similar to that of W. articulata, with two well-developed antapical horns, although the left is absent in some individuals. The apical and antapical horns are acuminate distally; the lateral horns are indented, denoting the position of a cingulum. The processes tend to be graded, being longest furthest away from the horns.
Affinities:
Williams and Downie, 1966, p. 189: Wetzeliella (Wetzeliella) tenuivirgula
In some specimens the majority of the processes are regularly arranged just within the plate boundary and form a simulate complex; they may also arise nearer the plate centre. The secae, besides uniting adjacent processes, often extend across the plate, thus giving rise to a very loosely knit reticulum, totally different, in appearance to that found in W. reticulata. Unconnected acuminate spines, up to 2-3 Ám in length, often arise from the interconnecting secae or trabeculae. The trabeculae may be granular or smooth; the secae are usually extremely fine and regular. Processes of adjacent plates are not united. The pre- or postcingular plates may or may not have processes on the side nearest the cingulum. The capsule almost fills the pericoel, apart from the horns, and has a slightly granular wall.
W. tenuivirgula differs from W. reticulata in the nature of the secae; in the latter species these are short and complexly anastomosing and are rarely unconnected.
Now Charlesdowniea. Originally Wetzeliella, subsequently Kisselovia, thirdly (and now) Charlesdowniea.
Holotype: Williams and Downie, 1966, pl.19, fig.2, 4; text-fig.49
Locus typicus: Sheppey, England
Stratum typicum: Early Eocene
Original diagnosis: Williams and Downie, 1966, p. 188: Wetzeliella (Wetzeliella) tenuivirgula
Periphragm outline pentagonal to ovoidal, with each angle produced into a well developed tapering horn--one apical, two lateral and one or two antapical. Right antapical horn always the longer. Periphragm flattened in cross section, save medially where it encloses the ovoidal capsule. Hollow, slender or branched processes arising from periphragm and arranged in simulate complexes or occurring haphazardly within complexes. Processes terminating distally in elongate, solid secae, sometimes united to secae of adjacent processes; giving rise to interconnections between processes on opposite sides of plate or remaining unconnected. Tabulation typical of genus, with three sulcal plates. Archaeopyle usually formed.
Dimensions: Periphragm, length 125--175 Ám; breadth 120--158 Ám. Capsule, length, 72-113 Ám; breadth 70-104 Ám.
Original description: Williams and Downie 1966, p. 189: Wetzeliella (Wetzeliella) tenuivirgula
W. tenuivirgula commonly has an outline similar to that of W. articulata, with two well-developed antapical horns, although the left is absent in some individuals. The apical and antapical horns are acuminate distally; the lateral horns are indented, denoting the position of a cingulum. The processes tend to be graded, being longest furthest away from the horns.
Affinities:
Williams and Downie, 1966, p. 189: Wetzeliella (Wetzeliella) tenuivirgula
In some specimens the majority of the processes are regularly arranged just within the plate boundary and form a simulate complex; they may also arise nearer the plate centre. The secae, besides uniting adjacent processes, often extend across the plate, thus giving rise to a very loosely knit reticulum, totally different, in appearance to that found in W. reticulata. Unconnected acuminate spines, up to 2-3 Ám in length, often arise from the interconnecting secae or trabeculae. The trabeculae may be granular or smooth; the secae are usually extremely fine and regular. Processes of adjacent plates are not united. The pre- or postcingular plates may or may not have processes on the side nearest the cingulum. The capsule almost fills the pericoel, apart from the horns, and has a slightly granular wall.
W. tenuivirgula differs from W. reticulata in the nature of the secae; in the latter species these are short and complexly anastomosing and are rarely unconnected.