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Eyachia
From Williams et al., 2017:
[Eyachia, Gocht, 1979, p. 307–308
Type species: Eyachia prisca, Gocht, 1979 (figs.9a–c)]
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Original description: Gocht, 1979: (Translation: Stover and Williams, 1987, p. 96):
Diagnosis:
Proximate to proximocavate dinoflagellate cysts with an oval to polygonal outline and a clearly defined paratabulation. Girdle and sulcus well
developed. With the exception of an apical projection, no large horns or processes are developed. Plates in the pre- and the postcingular series are typically nearly equal in size. Paratabulation formula: 1pr?, 4`, 5``, 6c, 6```, 1p, 1````.
Archeopyle (with complete development) formed through the loss of plates 2`` and 3`` as well as 1`-4` (Type 4A+2P, see Evitt, 1967).
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Modified description:
Stover and Williams, 1987, p. 96-97:
Synopsis:
Cysts proximate, subspherical to subpolygonal; paratabulation indicated by parasutural ridges, accessory ridges present on most paraplates; paratabulation formula: 1pr, 3`, 1a, 5``, 6c, 6```, 1p, 1````, ?s: archeopyle combined apical, intercalary and precingular, type [3A]+1I+2P formed by the release of two to four opercular pieces.
Description:
Shape: Subspherical to subpolygonal; epicyst smaller than hypocyst.
Wall relationships: Autophragm only; in SEM, two wall layers connected by irregularly spaced pillars are discernible.
Wall features: Parasutural ridges low and continuous; accessory ridges present on most paraplates and nontabular, pore-like perforations also
present.
Archeopyle: Combined apical, intercalary and precingular type [3A]+1I+2P; two to four opercular pieces released; generally 2P (2``+3``) only, or less commonly 2P (2``+3``) and I (1a), or rarely [3A] (1`,2`,3`) and 1I (1 a) and 2P (2``+3``).
Paratabulation: Indicated by parasutural ridges; formula: 1pr, 3`, 1a, 5``, 6c, 6```, 1p, 1````, ?s; hypocyst partiform, paraplates 1``` and 6``` nearly equal in size; paraplate 1p large (only slightly smaller than 1````) and located at or near the antapex.
Paracingulum: Indicated by six transversely elongate,rectangular paraplates; paracingulum nearer the anterior end than the posterior end.
Parasulcus: Indicated by bordering parasutural features; subdivision may be faintly indicated.
Size: Intermediate; about 60 to 75 µm in length.
Affinities:
Eyachia differs from Microdinium Cookson and Eisenack 1960; emended Stover and Evitt 1978 and from Histiocysta Davey 1969 in having a combined apical, intercalary and precingular archeopyle rather than a simple apical archeopyle and in possessing 5 instead of 6 precingular paraplates.
[Eyachia, Gocht, 1979, p. 307–308
Type species: Eyachia prisca, Gocht, 1979 (figs.9a–c)]
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Original description: Gocht, 1979: (Translation: Stover and Williams, 1987, p. 96):
Diagnosis:
Proximate to proximocavate dinoflagellate cysts with an oval to polygonal outline and a clearly defined paratabulation. Girdle and sulcus well
developed. With the exception of an apical projection, no large horns or processes are developed. Plates in the pre- and the postcingular series are typically nearly equal in size. Paratabulation formula: 1pr?, 4`, 5``, 6c, 6```, 1p, 1````.
Archeopyle (with complete development) formed through the loss of plates 2`` and 3`` as well as 1`-4` (Type 4A+2P, see Evitt, 1967).
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Modified description:
Stover and Williams, 1987, p. 96-97:
Synopsis:
Cysts proximate, subspherical to subpolygonal; paratabulation indicated by parasutural ridges, accessory ridges present on most paraplates; paratabulation formula: 1pr, 3`, 1a, 5``, 6c, 6```, 1p, 1````, ?s: archeopyle combined apical, intercalary and precingular, type [3A]+1I+2P formed by the release of two to four opercular pieces.
Description:
Shape: Subspherical to subpolygonal; epicyst smaller than hypocyst.
Wall relationships: Autophragm only; in SEM, two wall layers connected by irregularly spaced pillars are discernible.
Wall features: Parasutural ridges low and continuous; accessory ridges present on most paraplates and nontabular, pore-like perforations also
present.
Archeopyle: Combined apical, intercalary and precingular type [3A]+1I+2P; two to four opercular pieces released; generally 2P (2``+3``) only, or less commonly 2P (2``+3``) and I (1a), or rarely [3A] (1`,2`,3`) and 1I (1 a) and 2P (2``+3``).
Paratabulation: Indicated by parasutural ridges; formula: 1pr, 3`, 1a, 5``, 6c, 6```, 1p, 1````, ?s; hypocyst partiform, paraplates 1``` and 6``` nearly equal in size; paraplate 1p large (only slightly smaller than 1````) and located at or near the antapex.
Paracingulum: Indicated by six transversely elongate,rectangular paraplates; paracingulum nearer the anterior end than the posterior end.
Parasulcus: Indicated by bordering parasutural features; subdivision may be faintly indicated.
Size: Intermediate; about 60 to 75 µm in length.
Affinities:
Eyachia differs from Microdinium Cookson and Eisenack 1960; emended Stover and Evitt 1978 and from Histiocysta Davey 1969 in having a combined apical, intercalary and precingular archeopyle rather than a simple apical archeopyle and in possessing 5 instead of 6 precingular paraplates.