The rest of the shell is rolled towards the tooth in an anticlockwise direction, in order to remove it.
为了脱身，其余的壳就会以逆时针方向绕着牙齿旋转。
Even a small puncture to the shell, which a pointed tooth would be well able to deliver, would let the water in and cause that control to vanish.
即使在其外壳上有一个小小的穿刺，这点尖尖的牙齿驾轻就熟，也会让水渗入，造成浮力控制的消失。
That is why the recent discovery of a Jurassic ammonite with a shark's tooth embedded in its shell has excited palaeontologists.
这正是最近发现的一枚外壳中嵌有鲨鱼齿状物的侏罗纪鹦鹉螺化石令古生物学家兴奋的原因所在。
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