Comprehensive Description

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Pleurotomella? anomalapex n.sp., Pl. VI, fig. 19


Shell small, white, fusiform with strongly convex and weakly shouldered whorls, sculptured with dense, wavy, spiral lirations and protractively arcuately oblique axials. Whorls five, including a blunt paucispiral, smooth Protoconch of two whorls. Spire-whorls sculptured with ten to twelve spirals, body-whorl including base and neck with about forty-spirals, shoulder without spirals. Axial sculpture of narrowly rounded, oblique axials, which commence strongly at the shoulder, but become subobsolete over the lower half of the whorls. There is a weak surface pattern also, of dense axial threads which are more apparent on the otherwise smooth concave shoulder. The posterior sinus is deep, Daphnellid reversed L-shaped, and the outer lip swings forward in an arcuate sweep. The anterior canal is sharp and comparatively straight, its length emphasized by the relatively long neck, resulting from an excavated base.


Height 7.8 mm.; diameter 3.9 mm.


TYPE LOCALITY. St. WS 225. Between Falkland Is. and Patagonia, 50º 20’ S, 62º 30’ W, 9 June 1928, 162-161 m. (holotype only).


The species resembles ohlini, but has the addition of well-developed axials. Although both these species lack the sinusigerid protoconch of the genotype, the adult characters of build and sinus are in accord with Pleurotomella. I have already referred to Dall’s view that some Turrids commence with a horny sinusigerid envelope which wears off and leaves a limy mould in its place. The somewhat irregular shape and minute surface malleations of the nucleus in two of the above species, and especially the raised terminal varix, seem to be in accord with Dall’s explanation.”



(Powell, 1951: 173)


Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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