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Arkellea teichophera
Arkellea teichophera, (Sarjeant, 1961); Emendation: Below, 1990
Originally Cymatiosphaera, subsequently Heslertonia, thirdly (and now) Arkellea.
Holotype: Sarjeant, 1961, pl.16, fig.9; text-figs.9a-b; Sarjeant, 1976, pl.6, fig.3.
Age: Oxfordian.
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Original description as Cymatiosphaera teichophera: [Sarjeant, 1961, p. 107-108]:
Diagnosis:
Species of Cymatiosphaera having a broadly ellipsoidal shell divided into a low number (12-16) of polygonal fields. The membranes delimiting fields are high, their height equal to about one-third of the short diameter; they bear striations normal to the shell surfaces.
Description:
Shell walls of moderate thickness and of brownish-yellow colour. Fields vary considerably in size; their separating membranes are thin and relatively readily crumpled, lacking supporting spines at the junctions but having a distinct outer edge on to which striations do not extend.
Dimensions:
holotype: overall long diameter 50 µm. overall short diameter 40 µm, crests around 9 µm high.
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Emended description:
Below, 1990, p. 42-43:
Description:
Vesicle/plate arrangement on amphiesma cop, pop, cap, 3", 2a, 6"", 7c, 6""", 2"""", as, FM, ls, rs, ps; 1" exsert, adelopore on suture 1"/6""; 1a and 2a pentagonal. Growth of thecal plates ?gonyaulacoidal. Cyst murochorate, acavate, sphaeroidal ovaloidal, appearing polygonal because of high septa, epicyst smaller than hypocyst, equatorial section circular, oval, or flattened ventrally, maximal diameter at posterior cingular margin; wall consists of thin pedium and thin, homogenous luxuria with scabrate, chagrinate, microfrangate surface forming high, striate, finate septa.
Septa distally thickened, straight or deeply indented at irregular intervals or finely cut to form separate, finate processes; apical, sulcal and adsulcal areae and anterior adcingular septum are reduced to low ledges or groups of granae, and are often missing completely; as and 1" are always developed only as a single septum with gonal thickenings. Reduction of especially the ventral septa in the sulcal region lends the cyst its lenticular, ventrally flattened appearance.
Paratabulation XPR, 3", 2a, 6"", 7c, 6""", 2"""", Xs; PR is a small protruberance; 3 very unequally sized apicals against anterior intercalaries non- finate; 1" not reflected or merely as septum or process, VI-nE 2" (VL), VI-nE 3" (VR); 2 anterior intercalaries against each other nonfinate, but clearly rimmed by archaeopyle-sutures; camerate 1a (DL) and inverse-camerate 2a (DR); 6 precingulars against cingulum nonfinate; anteriorly geniculate V-nE 1"" (VVL), V-nE 2"" (LVL), V-nE 4"" (DDR)and V-nE 5"" (R), anteriorly linear IV-nE 3"" (DL) and V-nE 6"" (VVR), finis 4""/5"" dorsal; cingulum levorotatory, heptapartite, lati 1c-6c, iso 7c; 6 postcingulars: posteriorly linear IV-nE 1""" (LVL)(incompletely finate against sulcus), IV-nE 2""" (LVL), IV-nE 4""" (D), Iv-nE 5""" (DR), IV-nE 6""" (DR), posteriorly geniculate V-nE 3""" (DL); 2 antapicals: V 1"""" falling towards VL, polar VI 2""""; sulcus nonfinate internally but as and gonal contacts to rs/ls reflected as processes; archaeopyle anterior intercalary, 1a+2a; operculum solvate, opercular plates secate, general opercular formula 1a(s)+2a(s).
Originally Cymatiosphaera, subsequently Heslertonia, thirdly (and now) Arkellea.
Holotype: Sarjeant, 1961, pl.16, fig.9; text-figs.9a-b; Sarjeant, 1976, pl.6, fig.3.
Age: Oxfordian.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Cymatiosphaera teichophera: [Sarjeant, 1961, p. 107-108]:
Diagnosis:
Species of Cymatiosphaera having a broadly ellipsoidal shell divided into a low number (12-16) of polygonal fields. The membranes delimiting fields are high, their height equal to about one-third of the short diameter; they bear striations normal to the shell surfaces.
Description:
Shell walls of moderate thickness and of brownish-yellow colour. Fields vary considerably in size; their separating membranes are thin and relatively readily crumpled, lacking supporting spines at the junctions but having a distinct outer edge on to which striations do not extend.
Dimensions:
holotype: overall long diameter 50 µm. overall short diameter 40 µm, crests around 9 µm high.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Below, 1990, p. 42-43:
Description:
Vesicle/plate arrangement on amphiesma cop, pop, cap, 3", 2a, 6"", 7c, 6""", 2"""", as, FM, ls, rs, ps; 1" exsert, adelopore on suture 1"/6""; 1a and 2a pentagonal. Growth of thecal plates ?gonyaulacoidal. Cyst murochorate, acavate, sphaeroidal ovaloidal, appearing polygonal because of high septa, epicyst smaller than hypocyst, equatorial section circular, oval, or flattened ventrally, maximal diameter at posterior cingular margin; wall consists of thin pedium and thin, homogenous luxuria with scabrate, chagrinate, microfrangate surface forming high, striate, finate septa.
Septa distally thickened, straight or deeply indented at irregular intervals or finely cut to form separate, finate processes; apical, sulcal and adsulcal areae and anterior adcingular septum are reduced to low ledges or groups of granae, and are often missing completely; as and 1" are always developed only as a single septum with gonal thickenings. Reduction of especially the ventral septa in the sulcal region lends the cyst its lenticular, ventrally flattened appearance.
Paratabulation XPR, 3", 2a, 6"", 7c, 6""", 2"""", Xs; PR is a small protruberance; 3 very unequally sized apicals against anterior intercalaries non- finate; 1" not reflected or merely as septum or process, VI-nE 2" (VL), VI-nE 3" (VR); 2 anterior intercalaries against each other nonfinate, but clearly rimmed by archaeopyle-sutures; camerate 1a (DL) and inverse-camerate 2a (DR); 6 precingulars against cingulum nonfinate; anteriorly geniculate V-nE 1"" (VVL), V-nE 2"" (LVL), V-nE 4"" (DDR)and V-nE 5"" (R), anteriorly linear IV-nE 3"" (DL) and V-nE 6"" (VVR), finis 4""/5"" dorsal; cingulum levorotatory, heptapartite, lati 1c-6c, iso 7c; 6 postcingulars: posteriorly linear IV-nE 1""" (LVL)(incompletely finate against sulcus), IV-nE 2""" (LVL), IV-nE 4""" (D), Iv-nE 5""" (DR), IV-nE 6""" (DR), posteriorly geniculate V-nE 3""" (DL); 2 antapicals: V 1"""" falling towards VL, polar VI 2""""; sulcus nonfinate internally but as and gonal contacts to rs/ls reflected as processes; archaeopyle anterior intercalary, 1a+2a; operculum solvate, opercular plates secate, general opercular formula 1a(s)+2a(s).