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Xenikoon
From Williams et al., 2017:
[Xenikoon, Cookson and Eisenack 1960s, p. 14, 16
Type species: Xenikoon australis, Cookson and Eisenack, 1960s (pl.3, fig.17)]
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Original description: [Cookson and Eisenack, 1960]:
Shell ovoidal, slightly pointed anteriorly, containing a spherical capsule, the wall of which is in direct contact with the wall of the shell except at the anterior end. A pylome is present shortly below the apex. In one example, which unfortunately is damaged, the shell seems to have been enclosed in a smooth, outer membrane.
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Modified description:
Stover and Evitt, 1978, p. 133:
Synopsis:
Cysts proximate, epicavate, lenticular ellipsoidal, without distinct apical and antapical horns; endophragm outline elliptical, length greater than width; apical pericoel broad and low, always present; paratabulation indicated by archeopyle only, latter intercalary, Type l; archeopyle index <0.5.
Description:
Shape: Lenticular ellipsoidal.
Wall relationships: Cyst epicavate, endophragm and periphragm separated at apical end, pericoel relatively low.
Wall features: No parasutural features. Periphragm smooth, or faintly and uniformly ornamented.
Paratabulation: Indicated by archeopyle only.
Archeopyle: Intercalary, Type I or la (2a only); archeopyle index <0.5, generally about 0.4; whether operculum is normally free or attached is unknown.
Paracingulum: Not indicated.
Parasulcus: Not indicated.
Size: Intermediate.
Affinities:
Xenikoon differs from Nelsoniella in having a smaller (lower) apical pericoel. In addition, some species of Nelsoniella have an apical horn or protrusion. Xenikoon differs from Amphidiadema in lacking an antapical pericoel.
[Xenikoon, Cookson and Eisenack 1960s, p. 14, 16
Type species: Xenikoon australis, Cookson and Eisenack, 1960s (pl.3, fig.17)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Cookson and Eisenack, 1960]:
Shell ovoidal, slightly pointed anteriorly, containing a spherical capsule, the wall of which is in direct contact with the wall of the shell except at the anterior end. A pylome is present shortly below the apex. In one example, which unfortunately is damaged, the shell seems to have been enclosed in a smooth, outer membrane.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 133:
Synopsis:
Cysts proximate, epicavate, lenticular ellipsoidal, without distinct apical and antapical horns; endophragm outline elliptical, length greater than width; apical pericoel broad and low, always present; paratabulation indicated by archeopyle only, latter intercalary, Type l; archeopyle index <0.5.
Description:
Shape: Lenticular ellipsoidal.
Wall relationships: Cyst epicavate, endophragm and periphragm separated at apical end, pericoel relatively low.
Wall features: No parasutural features. Periphragm smooth, or faintly and uniformly ornamented.
Paratabulation: Indicated by archeopyle only.
Archeopyle: Intercalary, Type I or la (2a only); archeopyle index <0.5, generally about 0.4; whether operculum is normally free or attached is unknown.
Paracingulum: Not indicated.
Parasulcus: Not indicated.
Size: Intermediate.
Affinities:
Xenikoon differs from Nelsoniella in having a smaller (lower) apical pericoel. In addition, some species of Nelsoniella have an apical horn or protrusion. Xenikoon differs from Amphidiadema in lacking an antapical pericoel.