And you see that gill opening right there?

看到这里的鳃开口了吗？

Tertio, Conseil replied, The sturionians, whose gill opening is the usual single slit adorned with a gill cover, an order consisting of four genera. Example: the sturgeon.

第三目：鳍鱼，鳃跟平常的千样，只由一个有盖的孔开会；这一目有四科。类型：磺鱼。

Primo, the cyclostomes, whose jaws are fused into a flexible ring and whose gill openings are simply a large number of holes, an order consisting of only one family. Example: the lamprey.

第一目，圆口鱼，鳃合成为一个转动的圈环，鱼鳃开合有许多小孔，这一目只有一科。类型：人目鳗。