Semicassis labiata, common name the helmet bonnet shell, is a species of large predatory sea snail, a marine gastropod mollusc. This species is in the subfamily Cassinae, the "helmet shells" and "bonnet shells", which feed on sea urchins.Gofas, S. (2012). Semicassis labiata (Perry, 1811). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=533621 on 2012-07-15
Subspecies
Semicassis labiata iheringi (Carcelles, 1953)WoRMS (2010). Semicassis labiata. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=533621 on 2011-02-17 Semicassis labiata labiata (G. Perry, 1811) Semicassis labiata zeylanica (Lamarck, 1822)
Distribution This species occurs in New Zealand.Powell A. W. B. (1979). William Collins Publishers Ltd, Auckland . Along South Africa, it occurs off the West coast False Bay to KwaZulu-Natal north coast at subtidal depths up to 150 m.
Description The maximum recorded shell length of Semicassis labiata iheringi is 76 mm.Welch J. J. (2010). "The "Island Rule" and Deep-Sea Gastropods: Re-Examining the Evidence". PLoS ONE 5(1): e8776. . Also trawled at 70–75 m. depth, off São Paulo, Brazil.
The shell is rounded with a low but somewhat pointed spire. It is glossy and smooth, though often displaying one to two rows of low nodules in the shoulder region. In adult specimens, the outer lip is thickened, and the anterior end features a pronounced, up-curving siphonal notch. The shell shows significant variation in size, nodule prominence, thickness, and depth of coloration. Specimens from the Agulhas Bank tend to be larger, thinner, with weaker nodules and less vivid coloration. Here's an improved version of your description:
The color of the shell ranges from pale pinkish-brown to yellowish-brown, with some specimens featuring three to five rows of diffuse, semicircular whitish spots. The outer lip is marked by deep purple blotches, often appearing in pairs. Shell colors tend to fade significantly after death.
Habitat The minimum recorded depth of Semicassis labiata iheringi is 25 m, and the maximum recorded depth is 84 m.
References
Finlay, H. J. (1928). The Recent Mollusca of the Chatham Islands. Transactions of the New Zealand Institute. 59: 232–286. Dautzenberg, Ph. (1929). Mollusques testacés marins de Madagascar. Faune des Colonies Francaises, Tome III MacDonald & Co (1979). The MacDonald Encyclopedia of Shells. MacDonald & Co. London & Sydney. Spencer, H.G., Marshall, B.A. & Willan, R.C. (2009). Checklist of New Zealand living Mollusca. pp 196–219. in: Gordon, D.P. (ed.) New Zealand inventory of biodiversity. Volume one. Kingdom Animalia: Radiata, Lophotrochozoa, Deuterostomia. Canterbury University Press, Christchurch
External links Perry G. (1811). Conchology, or the natural history of shells: containing a new arrangement of the genera and species, illustrated by coloured engravings executed from the natural specimens, and including the latest discoveries. 4 pp., 61 plates. London