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Lithodinia amlasis
Lithodinia "amlasis" (Below, 1981a, p.58, pl.6, figs.14-15,16a-b) Williams et al., 1993, p.55. Holotype: Below, 1981a, pl.6, figs.16a-b; Fensome et al., 1991, figs.3-4 - p.567. NOW Meiourogonyaulax. Originally (and now) Meiourogonyaulax, subsequently Lithodinia. Age: Hauterivian.
Translation Below, 1981: Fensome, 1991, p. 568
Original diagnosis: Below, 1981, p. 58: Meiourogonyaulax amlasis
Proximate cyst with a two-layered wall. In transmitted light, the wall is thick, smooth and unstructured. Paratabulation is gonyaulacoid - 4", 6"", 6c, 6""", pc, 1"""", Xs - and is delineated by low, distally straight, smooth ribs. Paracingulum spiral, divided, offset by approximately twice its width at the undivided parasulcus. Archeopyle apical, type (A).
Original description: Below, 1981, p. 58
The essential difference from other species of the genus is in the development of the cyst wall. It is two-layered and the endophragm and periphragm are thick and structureless. It is evident under the SEM that the periphragm is smooth. Low, distally straight costae delimit the paraplates. The height of the boundary ridges varies. They may become almost completely reduced (see [Below, 1981a] pl.6, fig.14) or, especially on the hypocyst, they may be distinctly higher than in the holotype. In transmitted light they appear to be weakly alveolate. The paratabulation is similar to that of Meiourogonyaulax pertusa (Duxbury 1977) comb. nov. ssp. heta (see [Below, 1981a] p.56). The parasulcus is mostly not divided into ps, ra, and rs. The long, narrow 1"" is not separated from the longitudinal furrow. The archeopyle is apical. The "simple" operculum consists of four apical paraplates and is usually "enlarged".
Size. Holotype: length 66 Ám, width 60 Ám, height of parasutures 3.6 Ám. Range of other specimens: length 59(67)82 Ám, width 52(63)76 Ám, height of parasutures 0.5-8 Ám.
Translation Below, 1981: Fensome, 1991, p. 568
Original diagnosis: Below, 1981, p. 58: Meiourogonyaulax amlasis
Proximate cyst with a two-layered wall. In transmitted light, the wall is thick, smooth and unstructured. Paratabulation is gonyaulacoid - 4", 6"", 6c, 6""", pc, 1"""", Xs - and is delineated by low, distally straight, smooth ribs. Paracingulum spiral, divided, offset by approximately twice its width at the undivided parasulcus. Archeopyle apical, type (A).
Original description: Below, 1981, p. 58
The essential difference from other species of the genus is in the development of the cyst wall. It is two-layered and the endophragm and periphragm are thick and structureless. It is evident under the SEM that the periphragm is smooth. Low, distally straight costae delimit the paraplates. The height of the boundary ridges varies. They may become almost completely reduced (see [Below, 1981a] pl.6, fig.14) or, especially on the hypocyst, they may be distinctly higher than in the holotype. In transmitted light they appear to be weakly alveolate. The paratabulation is similar to that of Meiourogonyaulax pertusa (Duxbury 1977) comb. nov. ssp. heta (see [Below, 1981a] p.56). The parasulcus is mostly not divided into ps, ra, and rs. The long, narrow 1"" is not separated from the longitudinal furrow. The archeopyle is apical. The "simple" operculum consists of four apical paraplates and is usually "enlarged".
Size. Holotype: length 66 Ám, width 60 Ám, height of parasutures 3.6 Ám. Range of other specimens: length 59(67)82 Ám, width 52(63)76 Ám, height of parasutures 0.5-8 Ám.