Benham. — On the Viscera of Notornis. 155 



plate, in which ossification is just commencing. The third 

 ring (c) is somewhat larger, and its dorsal extremity on either 

 side curves round the bronchus. The fourth ring (d) is 

 stouter than the rest ; ventrally it presents a rounded knob, 

 which is produced downwards between the two bronchi : 

 thence it is continued dorsally, as the pessulus, in the angle 

 where the trachea divides to form the two bronchi. This 

 ring (d) is, like b, c, incomplete dorsally, the right and left 

 extremities curving round the upper part of each bronchus, 

 to cease at the membrana-tympanica interna. 



The pessulus is a straight long rod, continuous at its 

 ventral end with the ventral knob of the ring (d), but termi- 

 nates dorsally against a couple of small ossicles (r), which 

 are not coiinected with any ring, though possibly they do 

 become co-ossified with one in the adult bird. 



The remaining rings of the syrinx (e, f, g) call for little 

 remark ; they are incomplete internally, and embrace only 

 the outer surface of the bronchus, the inner surface of which 

 is formed by the membrana-tympanica interna. These three 

 bronchial half-rings are closely apposed externally, and the 

 lower margin of g is concave backwards. Between it and the 

 next bronchial ring (i), and between (i.) and (ii.) and between 

 (ii.) and (iii.), is stretched a thin membrane, the membrana- 

 tympanica externa. Then follow normal bronchial rings. 

 From the restriction of this membrane to the side of the 

 bronchus this kind of syrinx is termed a " bronchial syrinx." 



This apparatus of Notornis does not closely agree with any 

 that are figured in Bronn's "Thierreichs" by Gadow, nor with 

 other figures with which I have compared it ; hence I have 

 described it in some detail. The syrinx which is least unlike 

 that of Notornis is that figured l3y Beddard for JEgotheles 

 novcs-hoUandicB, so far as the arrangement of the membrana- 

 tympanica externa is concerned. 



There is one point in which Notornis appears to be 

 unique, though I am willing to admit that this may be due 

 merely to my ignorance of avian anatomy. According to 

 Gadow (in Bronn's "Thierreichs") the ring which carries the 

 pessulus is to be regarded as the last tracheal. Now, as I 

 have stated, the ventral end of this bone springs from the 

 fourth ring, which is therefore tracheal ; yet the dorsal ends 

 of this same ring undoubtedly belong to the bronchi, round 

 which they curve, for here indeed they are separated from the 

 trachea by the dorsal ends of the third ring. Consequently, a 

 ring is both tracheal and bronchial. This is a matter of 

 interpretation ; the facts are certain. 



Connected with the larynx various muscles have been 

 described. Of these, one, the bronchio-desmus, is stated to 

 be constant. However, I have failed to recognise it, unless 



