94 



PROF. W. B. BENHAM ON THE 



[Feb. 7, 



The ring c is somewhat larger, and its dorsal ends curve round 

 on to the inner surface of the bronchus and here cease. (Is it 

 therefore a bronchial ring ?) On the ventral middle line it is shghtly 

 dilated. 



rig. 4. 



The syrinx of Notornis, dorsal view (x 8). 



a-g. The modified rings of the syrinx ; 1-5, normal tracheal rings ; I to V, 

 normal bronchial rings ; i.t., membrana tympaniformis interna ; m, tracheo- 

 bronchial muscle ; o, portion of CESophagus ; p, origin of pessulus ; s, x, 

 accessory interannular cartilaginous nodules; y, ossicle; £•, muscle from 

 oesophagug to bronchus. 



The fourth syringeal ring {cl), when seen from the side, passes 

 straight across, and lies almost horizontally. It has a greater 

 diameter than the preceding, and projects as a knob ventrally. 

 Here it is produced backwards {p) and is continued dorsally 

 between the two bronchi to form the pessulus. But the dorsal end 

 of this same ring (rZ) curves round the bronchus on each side as 

 c does, and, like it, ceases against the " membrana tympaniformis 

 interna." 



The pessulus, which is directly connected with the ring d 

 at its ventral end, terminates dorsally against a couple of bones 

 situated at the angle formed by the two bronchi, which appear 



