蝙蝠的回声定位系统和飞行是区别于其他哺乳动物的两大特征。
Echolocation system and flight are two characters which distinguish bats from other mammalians .
在上周的讲座中，我们讨论了几种哺乳动物新生后代的特征。
In last week 's lecture , we discussed the characteristics of the newly born offspring of several mammals .
哺乳动物的特征