Alterbia rhombohedra, (Benson, 1976), Lentin and Williams, 1977

Combination illegitimate: the generic name Alterbia is illegitimate.

Holotype: Benson, 1976, pl.9, figs.10-12
Locus typicus: Round Bay, Maryland
Stratum typicum: Early Paleocene

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Original description as Deflandrea rhombohedra: [Benson, 1976, p. 195]:

Diagnosis:
Cavate cyst with left antapical horn strongly developed giving a rhomboid periblast shape. Cyst bilayered, endophragm slightly less than 1 µm, periphragm very delicate and considerably less than 0.5 µm.
Endoblast closely appressed to periblast with lateral pericoel being less than 1 µm. Endoblast protrudes into left antapical horn, position of right antapical horn frequently represented by a slight bulge or flattening on endoblast.
Atabulate.
Archeopyle intercalary (Type I/I).
Cingulum weakly developed, slightly levorotary, slightly depressed sulcus faintly evident with concavo-convex flagellar scar just posterior to plane of cingulum.
Endophragm smooth to microreticulate, periphragm smooth, may have faint wrinkles.

Dimensions:
Holotype: Periblast length 72 µm; width 35 µm; endoblast length 49 µm; width 33 µm; apical pericoel 9 µm.