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The operculum is not a product of the mantle. It is produced by a separate organ, the opercular disc, a pad of specialized secretory epithelial cells located right where the operculum is attached - on the posterior, dorsal aspect of the foot. The opercs of some species are secreted spirally, with new material being deposited on one edge only, and the operc gradually rotating on the opercular disc as it grows. Others are secreted oncentrically, with new conchiolin being deposited on all edges of the operculum simultaneously, without rotation of the operc.

Paul M.


I have promised several readers of Conch-L Net to give a more extensive answer concerning the use of opercula in the Middle East.

Henk K. Mienis
National Mollusc Collection
Dept. Evolution, Systematics & Ecology
Hebrew University of Jerusalem
IL-91904 Jerusalem, Israel

  • Human uses of opercula 1. Horny opercula used as "Ketoret" by Jews.
    • The use of "Ketoret" or the burning of spices for the production of incense has a long tradition in the Jewish faith. Several kinds of "Ketoret" were burnt on a special altar in the Holy Temples. However, with the fall of the Second Temple in Jerusalem (Early Roman period) the secret of burning one of these spices: "Shechelet" or "Zipporen" (= Hebrew for nail) got lost.
      At the same time another mollusc related secret became lost too: the method of producing the Biblical Blue or "Tekhelet" for dyeing the ritual fringes ("Tzitzit") of the prayer shawls ("Tallit").
      Various Jewish religious groups, believing in the rebuilding of the Third Temple and the subsequent appearing of the Messiah, are preparing themselves for that event by restoring ancient traditions. The source of the lost "Tekhelet" has been traced to the Banded Dye Murex: Hexaplex trunculus from the Mediterranean Sea (see various articles in E. Spanier (Ed.), 1987: The Royal Purple and the Biblical Blue. Keter Publ., Jerusalem).
      The source of the "Sechelet, Zipporen or Onycha" has still to be solved. Fortunately there are some indications. Linnaeus (1758: 747) mentioned in his "Systema Naturae" the scented nail or Unguis odoratus as being the operculum of "Muricum Purpurarum s. Frondesemtium". This subdivision of the genus Murex contained four species: ramosus, scorpio, saxatilis & erinaceus. Only Chicoreus ramosus or most probably the closely related Chicoreus virgineus (not known to Linnaeus), formed the most likely candidate for the production of this incense, since the latter is a common Red Sea species.
      However, most probably the opercula of several gastropods were exploited for this purpose. A Phoenician ship, sunken off the south coast of Turkey, contained in its hold among others many copper ingots packed together with large amounts of opercula. Three species could be identified: Hexaplex trunculus, Bolinus brandaris & Buccinulum corneum (Mienis, unpubl.). All three common Eastern Mediterranean species.
      In the same historic period both Hexaplex and Bolinus were already heavily exploited for the production of "Argaman - the Royal Purple" (and "Tekhelet - the Biblical Blue"?). So maybe part of the waste products: the opercula, were saved during that process for producing an other expensive item: the incense "Shechelet or Zipporen".
      Other possible candidates seem to be hiding among the Strombidae (see part 2).
  • Human uses of opercula 2. Horny opercula used as a source for incense in the Arabic world
    • The use of incense is not only part of an ancient Jewish tradition, but is also well rooted among both the Christian and Muslim Arabs in the Middle East.
      In Greek-Orthodox churches throughout the Levant incense is used as part of a daily ritual. However, I doubt whether horny opercula play a role in it.
      Muslims are making use of incense too. Most famous is the so-called frankincense obtained by burning the gum resin of Boswellia sacra, a rare tree confined in its distribution to parts of Dhofar and Yemen (see T. Mackintosh-Smith, 2000. Scents of Place - Frankinsence in Oman. Aramco World, 51 (3): 16-23). Up till today it is the most appreciated incense used throughout the Arabian Peninsula.
      Old Arabic medical books dating back to Mediaeval times describe the application of incense produced by burning horny opercula for curing several illnesses. Inhalation of such fumes was promoted for curing stomach pains, liver illnesses, epilepsy and regulation of the menstrual cycle. For this purpose the use of opercula of the following species was recommended: Strombus tricornis, Lambis truncata sebae, Chicoreus ramosus, Chicoreus virgineus & Pleuroploca trapezium i.e. the opercula of the largest gastropods living in the waters bordering the Arabian Peninsula. The best opercula were said to come from Jeddah. (see: M. Levey, 1961. Ibn Masawaih and his treatise on simple aromatic substances: studies in the history of Arabic Pharmacology I. J. Hist. Medicine & Allied Sci., 16: 407; M. Meyerhof & G.P. Sobhy, 1932. The abridged version of "The book of simple drugs", of Ahmad Ibn Muhammad Al-Ghafiqi by Gregorius Abul-Farag, 224-228. Cairo).
      I do not know whether the burning of horny opercula is still being applied as a home-made medical remedy. Noteworthy is the fact that in 1967 one of my colleagues at the Hebrew University noted still several glass jars filled with opercula of Strombus and Lambis in a pharmacy in Hebron!
  • Here is the first part dealing with calcareous opercula
    Human uses of opercula 3. Ornamental uses of Turbo opercula
    • The thick calcareous opercula of Turbo species have been exploited for a variety of ornamental purposes. Best known is the so-called Cat's eye: the operculum of the common Indo-Pacific species Turbo petholatus. Even today it is still used for the production of jewelry: rings, earrings and pendants.
      Similar sized opercula of other species have been used far less for the same purpose, although I have seen rings and pendants made out of the peculiarly pustulated operculum of the South African Turbo sarmaticus.
      Small Turbo opercula have been used also as eyes in such ethnographical objects as masks and fetishes (see: L. Pfeiffer, 1914. Die steinzeitliche Muscheltechniek und ihre Beziehungen zur Gegenwart, 15, fig. 12).
      The use of the heavy operculum of the Green Turban Turbo marmoratus as a paperweight has been wel documented in many popular shellbooks.
      On the Isle of Ifugoa, the Philippines, belts were made of opercula of Green Turban snails in which the large central specimen represented a deity causing difficulty by birth (see: J. Fearer Safer & F. McLaughlin Gill, 1982. Spirals of the Sea - an anthropological look at shells, 142 textfig.).
      Hardly known is the fact that the same huge opercula are being used locally for paving paths in Indonesia. An ornamental garden path in Sabang, Pulau We, Sumatera, has been described and illustrated by W.S.S. van Benthem Jutting (1950: Ornamental use of opercula of Turbo marmoratus. The Amsterdam Naturalist, 1 (3): 93-94, fig.2). The quoted figure shows the proud owner of the garden sitting near the entrance of his house with the "Turbo"-path stretching out in front of him. The path is 11 opercula wide, with the smooth convex sides of the opercula laying upwards, and is bordered at both sides by an additional operculum placed up right in the ground. This makes the path 13 opercula wide and at least 35 opercula long (the end of the path is not visible on the photograph), which means that at least 455 opercula had been used. The opercula were a byproduct of the local Turbo marmoratus fisheries for the Mother-of-Pearl industry
    • Noteworthy is still the fact that Turbo marmoratus (and Trochus niloticus) are still being fished on a commercial scale and even propagated artificially. A journal devoted to this subject is being published by the Secretariat of the Pacific Community in a printed and electronic form. All seven issues published so far are available at: www.spc.org.nc/coastfish/News/Trochus/Troc.html

  • This is the second part devoted to the use of calcareous opercula.
    Human uses of opercula 4. Shell beads made from opercula of the landsnail Pomatias olivieri
    • The Levant in general and Israel in particular is an eldorado for the archaeologist. Wherever you put a spade in the ground, sooner or later you will come across some relics from the past. If it is too hot to dig: wait for the winter rains, enter a ploughed field and have a look in the gullies worn out by short lived streams. Everywhere you will encounter numerous fragments of ceramic and glass ware, old coins, carnolian beads, etc. Usually shells are also among them: valves of Glycymeris insubrica, Cerastoderma glaucum or Acanthocardia tuberculata, often with a man-made hole in the umbo, or an occasional Cowry with the dorsum missing. These occasional finds of the latter have hardly any archaeological value since they are not found within the context of a particular cultural period, however, they give you always some satisfaction.

      Shells encountered during official excavations form more-and-more the subject of special studies and may supply the archaeologist with important information in the field of cultural habits, religion, food, climate, long-range contacts, etc. Unfortunately opercula are hardly encountered among such material.

      A noteworthy exception forms the Nahal Oren site in the Carmel range south of Haifa, Israel. During the excavation of that site, dating back to the Neolithic period (9500-6000 BP [= Before Present]), by the late Dr. Tamar Noy, 28 opercula were encountered.
      They turned out to belong to Pomatias olivieri, a terrestrial prosobranch still living today in the Carmel range. All the opercula, but two, showed a perfect round hole in the centre. These operculum served without doubt as shell beads, since shells were intensively used in the form of beads and pendants during the Neolithic period. A perforated operculum of Pomatias olivieri has been figured in Mienis (1990. Landsnails from a Neolithic site in Nahal Oren, Israel. The Papustyla, 1990 (5): 8-9; and 1990. Neolitische "kralen" vervaardigd uit opercula van Pomatias olivieri uit de opgravingen van Nahal Oren, Israel. C.B. Ned. Malac. Ver., 256: 728-731).

  • At the request of several correspondents some additional information concerning "Human uses of opercula"
    Human uses of opercula, 5. More information concerning Turbinidae
    • The use of opercula of Turban shells (Turbo) has been dealt with already in part 3 of this series (Conch L Net, 30 April, 2001). It was mainly dealing with the local exploitation of a by-product of the pearl button industry on Sumatera, Indonesia: the use of the large and heavy opercula of Turbo marmoratus for paving a garden path. In addition I mentioned briefly the use of opercula of smaller Turbo species in the jewelry industry. Additional gleanings of the literature have confirmed those statements, but also revealed some additional information.

      The local inhabitants of the Cocos-Keeling Islands, Eastern Indian Ocean, gather the opercula of Turbo petholatus, the Cat's Eye, for preparing jewelry (Orr Maes, 1967).

      James Hornell, former director of the Fisheries Department of Madras, India, and well-known author of several works on Indian molluscs, advised not only the use of the operculum of Turbo marmoratus as a paper weight, but also described how the local people collect the opercula of smaller Turbo species, especially Turbo argyrostoma. They are sold to pilgrims and devotees near the main entrance to the famous Rameswaram temple as "disc of the moon" (Tamil: ambiliman) (Hornell, 1917, 1922 & 1951).

      The same author also mentioned that a Turbinid species found in New Zealand containing an operculum brightly mottled with green and brown is highly valued by the Maoris as a personal ornament set in gold. They also used it to form the eyes of their idols in former times. Although Hornell (1922 & 1951) did not mention a more specific name, he was most probably referring to the Emerald Moon Turban Lunella smaragda, called by the Maoris Ataata.

      • Hornell, J., 1917. The edible molluscs of the Madras presidency. Madras Fisheries Bulletin, 11: 1-51.
      • Hornell, J., 1922. The common molluscs of south India. Madras Fisheries Bulletin, 14: 97-215.
      • Hornell, J, 1951. Indian molluscs. 96 pp. The Bombay Natural History Society, Bombay.
      • Orr Maes, V., 1967. The littoral marine mollusks of Cocos-Keeling Islands (Indian Ocean). Proc. Acad. Nat. Sci Philadelphia, 119 (4): 93-217.
This series of Henk's has been reproduced with his permission> (Avril)

In 1992 my friend Jack Austin wrote a piece on the reference to opercula incense in Exodus for the Victorian Branch of MAS newsletter. He wondered what species were used. I remembered that Dr.Donald Bosch had mentioned in a talk at COA that although shell collecting is not permitted in Oman, thousands of shells are collected for their opercula for use in incense, and that they are readily found in the markets. I later asked him which species were used. He said that it is mainly Cymatium boschi, Murex scolopax, Hexaplex kuesterianus, and Chicoreus ramosus. Eloise Bosch was kind enough to send me a booklet on Omani recipes which included a recipe for making bokhur, the incense. The booklet states:

  • "After kawha and dates, and perhaps fruit or halwah, visitors to an Omani home will be offered a tray of various perfumes in small ornate bottles. Following the perfumes, and incense burner with glowing coals is sprinkled with frankincense or bokhur and brought around to each guest in turn. The rich smoke is fanned into hair, beards, and clothing, whereupon the guest immediately says his goodbyes and departs in a cloud of fragrance."

Bill Clendenin
Sarasota, Florida


In Spain is usual the use of Turbo rugosum opercs in jewelry (they are called "orejones" -big ears-) and they are very appreciated just because its aesthetic look (they are cheap enough)


Alfonso Pina


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