rillstone

例句：

1. 1.The riverbed is covered with smooth rillstones.
   河床上铺满了光滑的卵石。
2. 2. The path was paved with smooth rillstones.
   这条路被平滑的卵石铺成了。
3. 3. The garden was landscaped with neatly arranged rillstones.
   花园里整齐排列着卵石。