per.i.os.tra.cum

n.（名詞）
【復(fù)數(shù)】 per.i.os.tra.ca[-k…]
The hard chitinous outer covering of the shell of many mollusks, especially freshwater ones, that protects the shell from the erosive action of water.
角質(zhì)層：許多軟體動物，尤指淡水軟體動物身體硬殼外包的一層物質(zhì)，用以防止殼受水的侵蝕作用

來源：
New Latin
現(xiàn)代拉丁語
peri-
peri-
Greek ostrakon [shell] * see ostracod
希臘語 ostrakon [殼] *參見 ostracod