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Webster 1913 Edition

Periostracum

‖

Perˊi-os′tra-cum

,

Noun.

;

pl.

Periostraca

(#)

.

[NL., fr. Gr.

περί

around + [GREEK] shell of a testacean.]

(Zool.)

A chitinous membrane covering the exterior of many shells; – called also

epidermis

.