Falsimargarita glaucophaos Barnard 1963

Falsimargarita glaucophaos (Barnard, 1963) *—new combination

(Figure 6A–D)

Calliostoma glaucophaos Barnard, 1963d: 442, fig. 8c. Kensley, 1973: 36, fig. 60. Springsteen, 1981: 5, fig. 12. Type loc.: 33°52ʹS: 16°51ʹE, 1380–1520 fathoms [ca 150 km due west of Table Bay, 2524–2780 m]; two syntypes in SAMC (A9830).

Minolia glaucophaos — Lussi, 2014: 14.

Distribution. Known only from the type material.

Notes. Barnard (1963d) referred this species to Calliostoma largely on the basis of its radula morphology, but he was clearly aware that it was not a typical member of that genus. The uniformly white shell with pink/green iridescence and strong spiral sculpture is much more typical of the genus Falsimargarita. Species of this genus are frequently described as having a large, smooth, rounded or inflated protoconch (Dell 1990; Warén & Bouchet 2001; Rios & Simone 2005; Simone 2008). Examination of the type material of C. glaucophaos indicates that it too has a large bulbous protoconch [diameter 0.9 mm (Barnard cited 1.0 mm), Fig. 4 D], which is effectively smooth under a dissecting microscope. There is no trace of the hexagonal sculpture so typical of Calliostoma and calliostomatids in general (Marshall 1995a). I have no hesitation in referring this species to Falsimargarita and note that it is extremely similar to F. stephaniae Rios & Simone, 2005 from 1200 m off the Falkland Islands. Indeed, allowing for some individual and geographic variation in shell size and the strength of the spiral sculpture, it is quite possible that the two are conspecific. The illustrations provided by Barnard (1963d) and Kensley (1973) suggest that F. glaucophaos is proportionately deeper [H:D close to 1.0] than F. stephaniae, but the dimensions of the syntypes (which match those provided by Barnard) give an H:D ratio of 0.88, which is the same as that calculated from the dimensions cited for F. stephaniae. Warén & Bouchet (2001) stated that the protoconch of Falsimargarita was finely tuberculate, but did not provide a figure. They noted also that this was at variance with the honey-comb sculpture of other calliostomatids.

Falsimargarita is primarily found in Antarctic and sub-Antarctic waters. Its occurrence at only ca 34°S is thus somewhat surprising, but may be related to the northward flow of cold Antarctic waters off the west coast of southern Africa. Warén & Bouchet (2001) have also recorded the genus from 17°25ʹS on the East Pacific Rise (2578 m) and from ‘deep-water dredgings’ off New Caledonia (25°S).