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periostracum
per·i·os·tra·cum P0195350 (pĕr′ē-ŏs′trə-kəm)n. pl. per·i·os·tra·ca (-kə) The tough horny or fibrous outer covering of the shell of many mollusks and brachiopods.
[New Latin : peri- + Greek ostrakon, shell; see ost- in Indo-European roots.]periostracum (ˌpɛrɪˈɒstrəkəm) n (Zoology) zoology the thin outer organic covering of a mollusc shell
periostracum
periostracum[‚per·ē′äs·trə·kəm] (invertebrate zoology) A protective layer of chitin covering the outer portion of the shell in many mollusks, especially fresh-water forms. periostracum
periostracum the outermost of the three layers of the shell of molluscs or brachiopods, composed of CONCHIOLIN. On the inner side lie the prismatic layer and the nacreous layer. |