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Escharina milneana (Busk, 1859)
Family: EscharinidaeGenus: Escharina
Colonies are encrusting, multiserial and sheet-like; Lagaaij (1952; see also Bishop & Hayward 1989, fig. 79) found vincularian colonies of this species in The Netherlands but this colony form has not yet been recorded in British material. The ancestrula and early astogeny are undescribed.
Autozooids are rhomboidal in outline shape, about 0.60 mm long by 0.35-0.45 mm wide (fide Lagaiij 1952, p. 70). The convex frontal shield is porous over its entire surface and has a granular texture. The primary orifice is hemielliptical, slit-like, much wider than long, about 0.07 mm long by 0.13 mm wide, with a small V-shaped sinus in the proximal edge. A thick peristome is present, outwardly flared especially on its proximal edge, which defines a secondary orifice less transversely elongated than the primary orifice. Oral spines are lacking. The ovicell is moderately small and prominent, with an ectooecium continuous with the frontal shield of the distal zooid and similarly covered by granules but lacking pores except at the very edges.
Adventitious avicularia are large, located proximolaterally of the orifice, one per zooid or sometimes absent, and have an inflated, imperforate cystid. The distolaterally or laterally directed rostrum is rounded arch-shaped and slightly narrower than the semicircular opesia from which it is separated by a calcified pivotal bar.