Deuterammina (Lepidodeuterammina) subgen. nov., and a redescription of Rotalina ochracea Williamson (Protozoa: Foraminiferida) P. Bronnimann Laboratoire de Paleontologie, Universite de Geneve, 13, rue des Maraichers, 1211 Geneve 4, Switzerland J. E. Whittaker Department of Palaeontology, British Museum (Natural History), Cromwell Road, London SW7 5BD, U.K. I. A lectotype for Rotalina ochracea Williamson Rotalina ochracea Williamson (1858) was based on three specimens obtained from 'sand from Shetland'. Spiral and umbilical views, probably of the same specimen, were illustrated (figs 112, 113) and the species was described in the classic monograph On the Recent Forami-nifera of Great Britain as follows (p. 55). . . Shell trochoid, depressed; slightly convex and smooth superiorly, correspondingly concave inferiorly; with about two and a half convolutions; arcuate; filled with brown animal matter, which is pale and translucent in the ultimate segments, but very dark and opaque in those near the umbilicus. Septa smooth in one specimen, a little elevated in another; broad, and of light ochraceous yellow, contrasting richly in the dark tint of the segments. The connecting spiral has the same ochraceous line. Inferiorly the segments of the last convolution extend nearly to the umbilicus, concealing the rest. Segments depressed or concave. Septal lines arcuate, flexuose and very prominent. Balkwill & Millett (1884) recognised the agglutinated nature of the test and transferred it to Trochammina. For a history of Trochammina, see Hedley et al, 1964 : 418. Although Trochammina ochracea (Williamson) is one of the most frequently reported species of the genus (see for instance, Heron-Allen & Earland, 1915; Cushman, 1920; Rhumbler, 1938; Hoglund, 1947; Todd & Low, 1961; Murray, 1971; Haynes, 1973; Lutze, 1974) its detailed morphology is for the most part poorly known. Williamson's figured specimen is, unfortu-nately, not in the remaining part of his collection in the British Museum (Natural History) and must be considered lost. The other two specimens (syntypes) are, however, extant and were figured by Hedley et al. (1964; figs 2, 3). In spite of this work, the species continues to be largely misidentified and it is now thought necessary to designate a lectotype and describe and illustrate the species afresh, using the benefits of scanning electron microscopy (SEM). Particular attention is paid to details of the apertures, in the light of recent advances in trochamminid taxonomy (see p. 236, below). The lectotype chosen bears the BMNH reg. no. 1963.2.19.16 and is illustrated in Figs 1-8, 10, herein. DESCRIPTION. (Lectotype). Test a concavo-convex, strongly compressed ('watch-glass' shaped) dextral trochospire comprising some 26 chambers arranged in almost 3 whorls, with 8 chambers in the final whorl. In outline the test is oval and slightly lobate; the periphery is rounded-compressed. Proloculus ellipsoidal 15xlOum in diameter. The chambers increase rapidly in size, those of the last whorl almost doubling in tangential diameter. Sutures curved and weakly depressed in the last whorl. Sutures on umbilical side strongly Bull. Br. Mus. nat Hist. (Zool.) 45(5): 233-238 Issued 29 September 1983 233
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