OCR Text |
Show 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 ?) O n the ventral middle line it is slightly dilated. Fig. 4. The syrinx of Notornis, dorsal view (x 8). a-y. The modified rings of the syrinx ; 1-5, normal tracheal rings ; I to V, normal bronchial rings; i.t., membrana tympaniformis interna ; m, tracheobronchial muscle; o, portion of oesophagus; p, origin of pessulus ; s, x, accessory interannular cartilaginous nodules; y, ossicle; z, muscle from oesophagus to bronchus. The fourth syringeal ring (d), 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 ventraily. 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 (d) 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, Avhich appear |