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Comprehensive Description

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Description

"Bulbus carcellesi n.sp. (Fig. 259)

 

MATERIAL EXAMINED: Eltanin Stns 339, 370, 944, 966, 967, 976; Hero Stn 470; off Bahia Blanca, Argentina, 200 m, ex E.C. Rios.

 

DISTRIBUTION: Known from off the Falklands, the Patagonian Shelf, Magellan Strait, off Tierra del Fuego and the coast of Argentina in 81-586 m.

 

DESCRIPTION: Shell large, globose, thin, spire variable in development but proportionately low, obtuse-angled to flattened, height greater than diameter. Whorls five, including a minute, smooth, domed protoconch not clearly marked off from teleoconch. Suture abutting, last whorl and base greatly expanded. Aperture very large, ovate, outer lip thin, retracted evenly from suture, inner lip spread rather thinly across parietal area. Columella somewhat thickened, relatively straight. Umbilicus obliterated from early age by development of parietal callus. Shell surface white, appearing polished, but under slight magnification with fine, close-spaced growth lines crossed by very fine, rather irregular spiral striae. Well-preserved specimens with a very thin, pale brownish-white periostracum. Operculum horny, thin, fragile, only slightly smaller than the aperture, pale brown in colour.

 

HOLOTYPE: from Eltanin Stn 944 in National Museum of Natural History (USNM 860110).

 

PARATYPE: from Eltanin Stn 944 in National Museum of New Zealand (one, MF.56601).

 

REMARKS: The shape is somewhat variable, most specimens having a slightly elevated spire, but some have the spire flattened and the last whorl more broadly swollen below the suture. Half-grown shells have the base much more attenuate, which gives the columella more prominence. On shell characters the new species is obviously allied to the northern hemisphere B. smithi Brown, 1839 and B. glacialis Thorson, 195 1, but it differs from both in the presence of fine spiral striae on the actual shell surface beneath the periostracum, and from smithi by the lack of an umbilicus. On shell characters B. carcellesi is reminiscent of the New Zealand genus Globisinum, which however lacks an operculum. The decision to refer this species to Bulbus is made more confidently since there are other forms in antarctic waters described below that also stem to belong in this group. Unfortunately, no animal was available, so the radula is unknown. This distinctive Magellanic species is named for the late Dr Alberto R. Carcelles in recognition of his work on the Mollusca of this region."

 

(Dell, 1990: 155-156)

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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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