海膽
A fine,sharp projection,as a spine of a sea urchin or a crystal. 針狀物精細(xì)尖銳的突出物，如海膽的脊椎骨或水晶球。
The hard outer shell of sea urchins are commonly called tests. 海膽的堅硬外殼通常被稱為甲殼。
