Ophthalmidium blackwilli – Mcfayden, W.A., 1939 [aff]. On Ophthalmidium, and two new names for Recent foraminifera of the family Ophthalmidiidae. Journ. Royal Microsc. Soc. London, ser.3, vol.59, p.166.
Description:Chamber arrangement is planispiral; comprising up to 12 windings of tubular chambers. Proloculus (30-40 µm in diameter) is followed by a closely coiled spiral tube, which may span from over two, to four windings; succeeded by up to eight or nine tubular segments, gradually decreasing in length from less than two windings, to one third or fourth of a whorl. As a result the sutures are somewhat irregularly dispersed along the spire. The initial chambers are tubular with a uniform diameter; later and larger chambers become successively more flattened. The periphery of the latest windings has a thin and semi-transparent wing along the outer margin only, with a thickened rim along the border. Aperture is circular to elongated, with somewhat thickened and everted lip; the septa cut obliquely across successive whorls. Surface is smooth and sutures are depressed. The largest specimen is 1,4 mm in diameter, but most are less than 1 mm. About 70 specimens were picked from 34 of the 1031 Bioice samples that were checked for forams; and in four miscellaneous samples.
Diagnosis: This species resembles superficially Ophthalmidium inconstans, but differs in lacking peripheral wings of the initial whorls; the latest adult chambers have a thin wing along the outer margin only, with a thickened rim along the margin.