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Nyktericysta
From Williams et al., 2017:
[Nyktericysta, Bint, 1986, p. 148-149; Emendations: Wan Chuanbiao and Zhang Ying, 1990, p. 6-7, 13; He Chengquan et al., 1992, p. 183-184, 190; Gao Ruiqi et al., 1992b, p. 35; Mao Shaozhi et al., 1999, p. 152.
Type species: Nyktericysta davisii, Bint, 1986 (pl.4, figs.1–2,5–6; text-figs.3A–B)]
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Original description: [Bint, 1986]:
Description:
Intermediate to large ceratioid cysts, compressed dorso-ventrally; shape dominated by wide-based, tapering apical and two subequal antapical horns, and two broad, blunt lateral horns. Left antapical horn is usually larger than right. Each lateral horn has a postcingular extension and an equally or less prominent precingular extension. Horn tips are closed and may be pointed or rounded, solid or hollow. Cysts two-walled and variably comucavate. Endocyst is produced into five prominent, terminally rounded horns. Periphragm is usually appressed to endophragm but variably separated from it at horns, either not at all, or with a small cavation at the tip of the apical horn only (with all other horn tips solid), or with pericoels beneath all five horns. Endophragm smooth, periphragm finely perforate and may be ornamented with features of low relief. Parasutures indicated by low ridges or locally dense ornament or, more commonly, not indicated.
Paratabulation ceratioid when expressed, but rarely completely developed. Paratabulation formula for fully paratabulate specimens, 4`, 6``, 5c, 6```, 1p, 1````. Paraplate 4` (Taylor-Evitt paraplate A) is short and does not reach the apex; 6" (li), 5c (fi), and 6`n (VIu) lie to the right of the sulcus within a defined ventral area which is very rarely subdivided - their presence is indicated but at most they are only partially outlined.
Cingulum indicated by indentation of the lateral horns and faint to distinct parasutural alignment.
Sulcus not indicated, except when paratabulation is well developed; extends almost to antapical concavity.
Archeopyle apical, operculum adnate ventrally, but often broken away. Archeopyle suture weakly angular to zigzag; in paratabulate forms it follows the boundary between apicals 2` (B) and 3` (C) and precingulars 2n-5" (3-6). There is no archeopyle suture mid-ventrally between apicals 1` (lu) and 4` (A) and their subjacent precingular paraplates.
[Nyktericysta, Bint, 1986, p. 148-149; Emendations: Wan Chuanbiao and Zhang Ying, 1990, p. 6-7, 13; He Chengquan et al., 1992, p. 183-184, 190; Gao Ruiqi et al., 1992b, p. 35; Mao Shaozhi et al., 1999, p. 152.
Type species: Nyktericysta davisii, Bint, 1986 (pl.4, figs.1–2,5–6; text-figs.3A–B)]
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Original description: [Bint, 1986]:
Description:
Intermediate to large ceratioid cysts, compressed dorso-ventrally; shape dominated by wide-based, tapering apical and two subequal antapical horns, and two broad, blunt lateral horns. Left antapical horn is usually larger than right. Each lateral horn has a postcingular extension and an equally or less prominent precingular extension. Horn tips are closed and may be pointed or rounded, solid or hollow. Cysts two-walled and variably comucavate. Endocyst is produced into five prominent, terminally rounded horns. Periphragm is usually appressed to endophragm but variably separated from it at horns, either not at all, or with a small cavation at the tip of the apical horn only (with all other horn tips solid), or with pericoels beneath all five horns. Endophragm smooth, periphragm finely perforate and may be ornamented with features of low relief. Parasutures indicated by low ridges or locally dense ornament or, more commonly, not indicated.
Paratabulation ceratioid when expressed, but rarely completely developed. Paratabulation formula for fully paratabulate specimens, 4`, 6``, 5c, 6```, 1p, 1````. Paraplate 4` (Taylor-Evitt paraplate A) is short and does not reach the apex; 6" (li), 5c (fi), and 6`n (VIu) lie to the right of the sulcus within a defined ventral area which is very rarely subdivided - their presence is indicated but at most they are only partially outlined.
Cingulum indicated by indentation of the lateral horns and faint to distinct parasutural alignment.
Sulcus not indicated, except when paratabulation is well developed; extends almost to antapical concavity.
Archeopyle apical, operculum adnate ventrally, but often broken away. Archeopyle suture weakly angular to zigzag; in paratabulate forms it follows the boundary between apicals 2` (B) and 3` (C) and precingulars 2n-5" (3-6). There is no archeopyle suture mid-ventrally between apicals 1` (lu) and 4` (A) and their subjacent precingular paraplates.