780 MR. W, A. FORBES ON THE [June 21, 



rings are here, as elsewhere, entire simple rings, of an average depth 

 of about '15 inch, and are separated only by very slight interannular 

 intervals. The trachea is slightly compressed and posteriorly 

 carinated for about the last 7 rings. The last ring but four is 

 somewhat produced downwards in the middle line, both anteriorly and 

 posteriorly ; it is, in consequence, narrower laterally than elsewhere. 

 The antepenultimate ring presents the same features more strongly 

 developed. In two of the four specimens examined it sends down a 

 small pessuliform process of cartilage in the middle line behind, 

 filling the chink left between the posterior extremities of the two 

 next (incomplete) rings. The penultimate ring is narrower and 

 more cylindrical than its predecessors ; it is also wider transversely, 

 and incomplete behind in the middle line, its extremities, however, 

 being closely approximated to each other. The last tracheal ring 

 is still wider transversely, and more cylindrical ; and it too is incom- 

 plete posteriorly, to a greater extent than its predecessor ; viewed 

 from the side it is convex upwards, as are its few immediate pre- 

 decessors in a less degree. The interannular intervals between all 

 these rings are, when undisturbed, mere chinks filled up by dense 

 fibrous and elastic tissues. There is no trace of a pessulus, though 

 the last tracheal ring is slightly produced downwards in front. The 

 first bronchial semiring, on each side, is narrow and cyHndrical, 

 strongest anteriorly, and somewhat attenuated posteriorly. It is 

 separated only by a narrow interval from the last tracheal ring. The 

 second and third rings are similar, but are more slender and lengthy ; 

 they are convex downwards, but very slightly so ; hence the inter- 

 annular intervals are small here also. Their anterior ends are very 

 slightly iuturned, impinging but to a small extent on the membrana 

 tympaniformis, which completes the bronchial tubes internally, and, 

 in consequence of the absence of any three-way piece, passes con- 

 tinuously from, one bronchus to the other, so closing the tracheal tube 

 inferiorly. The fourth, fifth, and succeeding bronchial rings are 

 similar in character ; but their ends, which tend to be dilated pos- 

 teriorly, are successively more and more incurved to about the tenth. 

 Nowhere are the bronchial rings complete. 



There is, at most, only a trace of a membrana semilunaris, in the 

 form of a very feeble, scarcely raised, antero-posteriorly directed 

 fold of mucous membrane. 



Internally, the mucous membrane of the interior is greatly 

 thickened, forming a vocal cord, in the region of the last three 

 tracheal rings and first two bronchial semirings (vide fig. 1, b). 



There is no trace of any intrinsic voice-muscle ; and the lateral tra- 

 cheal muscles stop at the point of insertion of the sterno-tracheales. 



The genus Ajiteri/x, in the simplicity of the structure of its lower 

 larynx, stands on the same level as Struthio. In Apteryx mantelli 

 (figs. 3, 4) about the last dozen tracheal rings are quite simple in 

 form, with narrow interannular intervals, and no anterior and 

 posterior notching. The penultimate ring is produced slightly 

 downwards, in a triangular way, both anteriorly and posteriorly. 

 The last ring is also produced downwards anteriorly, but is incom- 



