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Conus virgo
Recently Cernohorsky (1964, Sean Raynon Sabado, NS #54:6) has figured similar abnormalities from Mauritius, but they also
occur in Queensland: Iredale (1939, Austr. Zoologist 9:319, pl. 29, fig. 24-26) figured rostrate melanistic Melicerona
listeri Gray (called by him M. melvilli velesia Iredale) from the Capricorn Islands, and I possess similar shells from Wilson
Island off Gladstone (leg. A. Nash 1954).
Besides, Mr. Cedric Coucom told me by letter that Pumpkin Island, (about one mile south of North Keppel Island and about 8.5
miles E.N.E. of Yeppoon) yielded wonderful specimens of melanistic cowries.
He described this "shell collector's paradise" as follows: "The island comprises two elevated pieces of land divided by a
narrow channel which goes dry at low tide. Coral is present here and sea weed is plentiful." The Keppel Islands lie within
"the area covered by fresh water when the Fitzroy river is in flood," which fact may affect the cowries. In May, 1964, Mr.
Coucom collected some more rostrate, melanistic Erronea errones Linnaeus and Purpuradusta gracilis macula Angas at the same
place, and presented them to the writer; one extremely rostrate shell of each species has been figured above: fig. 1 - 3
represents the base, dorsum, and columellar margin of errones (coll. Schilder 17856: length 25.6 mm), fig. 4 - 6 represents
the same views of macula (coll. Schilder 17862: length 20.8 mm).
The cause of rostration is still doubtful: explanations range from hurts of the mantle (Sullioti 1924) to living in muddy
bottom (Schilder 1927, 1938) or on sea fans (Tomlin by letter about in 1930), and influence of metals (Cernohorsky 1962);
surely it should be regarded as modification, and not as hereditary. Any solution of the problem must consider the following
five facts:
C. erosa erosa Linnaeus, 1758
The specimen was collected by Mrs. Couacaud at Grand Bay, Mauritius, exposed on basalt rocks. A similar specimen had been
described by Sowerby as C. caurica var. concava (Thes. Conch., pl. 29 (320), figs. 318-319), from Owen's collection.
The C. erosa erosa Linnaeus, 1758, is not melanistic but is considerably rostrate; this had also been collected by Mrs.
Couacaud at Mauritius.
Dr. Schilder, who had the opportunity to view the photographs, commented as follows (in litt.): "The rostration of the shells
is not absolutely the same as that of New Caledonian cowries. The features of C. erosa may be comparable to those from New
Caledonia, though details are aberrant, especially the thickening of the posterior quarter and the total absence of melanism;
the cause of malformation may thus be different. The C. caurica shows quite peculiar features, e.g. total reduction of the
teeth and abnormal dilatation of the aperture in front, features which recall C. tortirostris."
Rostration does not necessarily have to be combined with melanism; specimens of C. clandestina and C. lynx which I collected
in New Caledonia were rostrate but not melanistic; a C. caurica collected at the Bay du Mondoure, was both rostrate and
melanistic, with a grossly dilated anterior aperture.
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