Abstract
Abstract. This study presents a revision, using type material, of the tiny foraminifera Discorbina minutissima Chaster, D. chasteri Heron-Allen & Earland (erected as a nomen novum for D. minutissima Chaster, non Seguenza) and D. chasteri var. bispinosa Heron-Allen & Earland. All are referred to the genus Rotaliella Grell. Heron-Allen & Earland’s new name chasteri is shown to be only applicable as a replacement name for Chaster’s species; their own material from Clare Island is a new species, named here R. heronalleni sp.nov. In addition, two other species — Rotaliella ? simplex (Sidebottom) and R. antarctica sp.nov. — have been recognised amongst the specimens labelled as D. chasteri in the Heron-Allen & Earland Collection in the Natural History Museum (BMNH). Lectotypes are designated for Rotaliella chasteri and R. bispinosa.
Highlights
While working on the minute benthic foraminifera of the Gulf of Elat and the NE Atlantic,we found a few specimens which resemble the species Discorbina minutissima and D.chasteri auctt
We propose to raise Discorbina chusteri var. bispinosa Heron-Allen& Earland to specificstatus, asRotaliella bispinosa
Recorded as Discorbina chusteri, it is found in the South Atlantic and Antarctica, in the following localities: the Ross Sea (HeronAllen & Earland, 1922), the Falkland Islands (Heron-Allen & Earland, 1932; Earland, 1934) and South Georgia (Earland, 1933).It was most abundant at 'Terra Nova' station 220, off Cape Adare, depth 80-90m, in sediments composed mostly of organicdebris,hydrozoan fragments,diatoms, sponge spicules and mineral particles
Summary
While working on the minute benthic foraminifera of the Gulf of Elat and the NE Atlantic,we found a few specimens which resemble the species Discorbina minutissima and D.chasteri auctt. The original descriptions and illustrations of these tiny species,whose test diameters average only 100microns, were made by Chaster (1892) and Heron-Allen & Earland (1913), respectively. His monograph of the Foraminifera of the Atlantic Ocean, he described chasteri and illustrated it with a copy of the original drawinds by Heron-Allen & Earland (1913) and pictures of two specimens collected off the Faroe Islands, at 128 metres, sent to him by Earland. A distinctive character of Rotnlielln, ,isa small,hemisphericalor elongated space, situated between the proloculus and the subsequent two chambers, which is visible as a prolocular boss on the spiral side;this structurewas called the ’Zwischenkammer’by Grell(1954),who suggested that this is an additional chamber formed during the embryonic stage It seems, that this’prolocular boss’ is a pseudochamber, rather than a real chamber, as it never contains the cytoplasm (this is based on the original illustration of Rotalielln heterocnryoticn Grell(l954) and our own observations of cultured species of Rotalielln). We have designated a lectotypefromchaster’s material.Thisis referred to Rotnlielln clrnsteri (Heron-Allen & Earland), as their iiomw nouiiiii was erected as a replacementname for riiirrirtissirrrrr (noir Seguenza, 1880).The other species, as illustrated by Heron-
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