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，鳃跟平常千样，只由一个有孔开会；这一目有四科。类：磺鱼。

So Eusthenopteron was maybe breathing air in addition to water, and since the hole was close to the front of the face, they probably used their gills to handle both.

所以诺鱼可能既在水中也在空气中呼吸，由于这个孔靠近面部前方，它们可能使用鳃来处理这两种呼吸方式。