BRANCHIARUM foramina, apertures of the gills. In most fishes there is only one aperture; in the cartilaginous ones, these apertures are ten in number, five on each side; and in the petromyzon or lamprey, there are no less than fourteen of these apertures, seven on each side.
As to the cetaceous fishes, they have no aperture of this kind; and the reason seems to be, because they are furnished with lungs.