Onycha

on´i - ka ( שחלת , sheḥēleth ; compare Arabic suḥâlat , "filings," "husks"): "Onycha" is a transliteration of the Septuagint ὄνυχα , ónucha , accusative of ὄνυξ , ónux , which means "nail," "claw," "hoof," and also "onyx," a precious stone. The form "onycha" was perhaps chosen to avoid confusion with "onyx," the stone. The Hebrew sheḥēleth occurs only in Exodus 30:34 as an ingredient of the sacred incense. It is supposed to denote the horny operculum found in certain species of marine gasteropod molluscs. The operculum is a disk attached to the upper side of the hinder part of the "foot" of the mollusc. When the animal draws itself into its shell, the hinder part of the foot comes last, and the operculum closes the mouth of the shell. The operculum, which may be horny or stony, is absent in some species. The horny opercula when burned emit a peculiar odor, and are still used in combination with other perfumes by the Arab women of Upper Egypt and Nubia. (See Sir S. Baker, The Nile Tributaries of Abyssinia , cited by EB , under the word "Onycha.")