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Conus marmoreus Linnaeus 1758

Like all cones, C. marmoreus (Marble Cone) is predatory and uses its venomous sting both to defend itself and capture prey. It is molluscivorous, which is to say that it feeds on other mollusks.

Contrary to what one reads on the Web, C. marmoreus is not one of the world's most poisonous (venomous) animals. Only one sting has been reported (in 1877), the outcome of which is not known. Its radular tooth is considerably shorter than those of other molluscivorous species and comparable to vermivores, which hunt marine worms. Because it does not feed on fish (the dangerous cones, which must immobilize their prey quickly, are piscivorous), Endean and Rudkin have concluded that C. marmoreus is "harmless to man." Rather, the most lethal species of cone is Conus geographus (Geography Cone), which is reported to have caused more than thirty human fatalities. Olivera has compared the neuromuscular effect of its sting to being bitten by a cobra while eating a lethal portion of fugu.

C. marmoreus was the first species of cone shell to have been described by Linnaeus (Systema Naturae, 10th ed., 1758), who used the specimen in his own collection as the lectotype. As the type species, it therefore defined the genus Conus. (So, too, the Marble Cone is the first of more than three hundred species cataloged in the Manual of the Living Conidae.) The illustration (right) is from the third edition of d'Argenville's Conchyliologie (1780, Pl. XIV, fig. E4) and is the same figure that appeared in the first edition (1742), which Linnaeus had referenced in his description of the shell.

 


This etching is the only example of an object from Rembrandt's cabinet of natural curiosities and his only still-life. Too, it survives in relatively few impressions. As often was the custom, Rembrandt drew the shell as he saw it. The result is that, even though the plate has been signed and dated correctly, the image itself is reversed.

In March 1637, Rembrandt purchased a conch shell for the extravagant sum of eleven guilders. It was such acquisitions that contributed to his bankruptcy in 1656, when all his belongings were auctioned, including "a great quantity of shells [and] coral branches."


Lesson XII:

Teacher. If any one were now to speak to you of a Conus, what idea would the name call up to your mind?

Child. The name Conus would recall the idea of a univalve shell, whose form is inversely conical and turbinate; the spire retuse; whorls spirally convoluted, aperture linear, longitudinal, entire, effuse at the base; its columellar lip smooth, having sometimes a few oblique rugose striae towards its base.

Teacher. Yes, all the shells before us posses these qualities, or they would not be Cones:—but are they alike in all respects?

Child. No ; they differ very much in their colours and patterns, and also in their size.

Teacher. On account of this variety in the shells possessing the same generic marks, the different genera have been subdivided into species, the characters of which are determined by—the circumstances of colour, markings, size, and the inequalities of the surface. Here is a shell called Conus marmoreus: I wish you to examine it, and draw out its specific character; it is considered as the type or representative of the Conus, from its having the characteristics of the genus strongly marked. Now, tell me what you have to do.

Child. We must try and describe this shell.

Teacher. Yes; but you must recollect that you have to point out the specific distinctions only; you must now omit the generic marks, as you have already determined them, and they are implied in the name Conus. First, what is the size of this Cone?

Child. It is rather more than two inches long.

Teacher. Yes, in length it generally varies from two to three inches. What is the colour of the shell, and that of its markings?

Child. The ground is a dark chesnut brown, approaching to black, and the markings are white.

Teacher. What form do the spots most nearly resemble?

Child. They are nearly triangular.

Teacher. You may call them white subtriangular spots; sub means under, and when prefixed to an adjective implies that the quality attributed to the object, exists in an inferior degree. Examine the substance of the shell.

Child. It is heavy and thick.

Teacher. It is a ponderous shell; now look at the spire, and tell me what you remark in it.

Child. It has little swellings placed regularly at the edges of the whorls.

Teacher. These swellings are called tubercles, and a spire marked with such inequalities is said to be coronated.

Child. I suppose that means crowned.

Teacher. Yes, the spire is so called from its crown-like appearance; do you observe any other peculiarity in it?

Child. The whorls are concave, and in most shells they are convex.

Teacher. The whorls in this shell form a little spiral channel, and are thence said to be channelled. We will now write down the specific character; but I must inform you, that the name marmoreas is derived from the Latin marmor, marble; and is applied to these shells on account of their mottled appearance.

Lessons on Shells: As Given to Children Between the Ages of Eight and Ten in a Pestalozzian School, at Cheam, Surrey (1838) by Elizabeth Mayo


A note on nomenclature: The family Conidae comprises only one genus Conus, which more popularly is known as cone snails or cone shells. These mollusks are venomous, which is to say that they inject their toxin. A poisonous animal (such as the puffer fish) must be ingested for its toxin to take effect. And, although "bite" often is used for convenience, the modified radular tooth of the cone snail is not comparable to that of a vertebrate, and "sting" is a more accurate description of the pricking of the skin by Conus.


References: Linnaeus: Systema naturae (1758, p.712, no.250); Manual of the Living Conidae (1995) by Dieter Röckel, Werner Korn, and Alan J. Kohn; "Studies of the Venoms of Some Conidae" (1963) by R. Endean and Clare Rudkin, Toxicon, 1, 49-64; "Conus Peptides, Pt.1" (May 2006) by Baldomero Olivera, The American Society for Cell Biology (online iBioSeminars); "Venomous Marine Snails of the Genus Conus" (1963) by A. J. Kohn, in Venomous and Poisonous Animals and Noxious Plants of the Pacific Area edited by Hugh L. Keegan and W. V. Macfarlane; "The Poison Cone Shell" (1943) by William J. Clench and Yoshio Kondo, American Journal of Tropical Medicine, 23, 105-122; "Snail Spears and Scimitars: A Character Analysis of Conus Radular Teeth" (1999) by Alan J. Kohn, Manami Nishi, and Bruno Pernet, Journal of Molluscan Studies, 65, 461-481.

After the death of d'Argenville in 1765, a third edition of his La Conchyliologie was produced by Jacques de Favanne and son in 1780 that included not only the shells from earlier editions but specimens from other collections. The eighty colored plates that illustrated this posthumous edition have been reprinted by Taschen in Antoine-Joseph Dezallier d'Argenville: Shells (2009) by Veronica Carpita, Rainer Willmann, and Sophia Willmann.

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