(n.) A chitinous membrane covering the exterior of many shells; -- called also epidermis.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). periostracum. Retrieved September 23, 2026, from http://smartdefine.org/periostracum/definitions/2043880 |
| Chicago | Webster's. 2011. "periostracum" http://smartdefine.org/periostracum/definitions/2043880 (accessed September 23, 2026). |
| Harvard | Webster's 2011, periostracum, Smart Define, viewed 23 September, 2026, <http://smartdefine.org/periostracum/definitions/2043880>. |
| MLA | Webster's. "periostracum" 27 May 2011. Web. 23 September 2026. <http://smartdefine.org/periostracum/definitions/2043880> |