Any of various primitive eellike vertebrates of the class Agnatha, such as a lamprey, lacking jaws and true teeth and having a circular, sucking mouth.
英
美
- 圆口纲脊椎动物一种类似鳗鱼的无颚纲原始脊椎动物,如盲鳗,没有下颚和真正的牙齿,而长着圆形吮吸的嘴