Fifteen million years ago, these giant marine cities 1500万年前 这些巨大的海洋城市
fifteen centimeters long, snaps up everything in it's path. 仅15厘米长.边游边大快朵颐
Individuals link together to form chains which can stretch for fifteen meters. 这些一个个单体组成的链条可长达15米
These vast aquatic grasslands stretch for fifteen hundred square miles 这片广大的海洋牧场 面积可达1500平方英里