THE NARWAL. 85 



inch and a half in length. It expands immediate- 

 ly within the skin into a sac or air vessel, six or 

 eight inches wide, and extending laterally and for- 

 ward, into two cavities, one on each side; the ex- 

 tremities of which, are about twelve inches apart. 

 These contain some mucous matter; the lining of 

 the whole sac is a thin, greenish, black membrane. 

 At the posterior extremity of the sac, the blowholes 

 are seen, divided there, into two distinct canals 

 in the skull. They are closed by a valve resem- 

 bling a hare lip, one lobe of which covers each 

 canal. This valve in the narwal, does not, (as in 

 the whale), enter the canal in the skull, but merely 

 closes down upon it. It, however, effectually ex- 

 cludes the sea-water from the lungs, whatever be the 

 pressure; it becomes, in fact, firmer and closer, in 

 proportion as the weight of water is increased. The 

 valve is about six inches wide and is closed and 

 opened by two radiated muscles. It is detach- 

 ed from the skull beneath, about six inches to- 

 wards the snout. In consequence of this separa- 

 tion, the valve is sufficiently free, and has room 

 enough in the adjoining sac to be drawn upward 

 and forward, so as to expose the breathing canals, 

 or falling upon them like the valve of a pump-box, 

 to secure them against the entrance of water. The 

 two lobes of the valve are connected by a fleshy 

 septum, slightly attached to the cartilaginous part of 

 the bony partition between the blow-holes in the 

 skull. 



