外卵壳

例句：

1. 1.The turtle's outer shell is thick and tough.
   乌龟的外壳又厚又硬。
2. 2.The baby chicks hatched from the eggs are covered in soft down.
   从蛋里孵化出来的小鸡身上覆盖着柔软的绒毛。
3. 3. The scientist studied the outer shell of the dinosaur to learn more about its evolution.
   这位科学家研究了恐龙的外骨骼，以了解其进化过程。