1881.] TRACHEA IN THE " RATITE " BIRDS. 7S7 



in the structure of its syrinx. In the single specimen I have by me, 

 the tympanic box is anteriorly marked by four sutures on one side, 

 and by three only on the other, as sometimes happens in R. ameri- 

 cana (as, e. g., in the specimen described and figured above). 



Reviewing the facts herein detailed, the most striking fact that 

 comes out is the great difference exhibited by Hhea when compared 

 with the four other genera described. In the possession of a tracheal 

 box formed by the fusion of the few last tracheal rings, in the 

 greater amount of specialization of the first two bronchial semirings 

 of each side, in the presence of distinct interannular membrane-covered 

 fenestrse, in the development of a well-marked cartWaginous pessuhis, 

 and in the possession of a pair of true intrinsic syringeal muscles run- 

 ning from the trachea to the bronchial semirings Hhea stands out by 

 itself as sharply opposed to all the remaining "Ratite" birds. Of the 

 latter, Struthio and Apteryx, as far as regards tracheal structure, 

 form one group, the Casuariidae another, the difference between the 

 two being, however, comparatively slight as compared with those 

 between them generally and Rhea. 



Struthio and Apteryx, in the tendency of the trachea to narrow 

 before its bifurcation, in the greater amount of solidity of the 

 cartilaginous structures, in the more sharply-defined junction be- 

 between the two constituent parts of the bifurcating trachea, owing 

 to the better development of the few last tracheal rings, differ 

 from the Casuariidae, where the terminal part of the trachea tends to 

 develop into an expanded tympanum, the cartilaginous structures 

 are softer and more pliant, the terminal tracheal rings are narrower 

 and tend, especially in Casuarius, to become imperfect posteriorly, 

 and the junction of trachea and bronchi is less marked. In the 

 Casuariidse, too, the insertion of the sterno-tracheales is different 

 from that of the other genera. 



As regards the alleged absence of a lower larynx (or " syrinx ") 

 in these " Ratite " birds, it is obviously untrue as regards the genus 

 Rhea. In the other genera, an answer is less easy, and its nature 

 must depend upon what is meant by the term " lower larynx." 



The presence of intrinsic voice-muscles cannot be regarded as 

 essential in the definition of that term, any more than the develop- 

 ment of a jsessw/MS ; indeed either or both (e.g. Conopophaga) may 

 be absent in birds with well-developed vocal organs. If the presence 

 of semirings externally, and of a viembrana tympuniformis internally, 

 forming the walls of the bronchi, and of vocal cords developed in the 

 interior of those tubes, be held to be sufficient to characterize a 

 "syrinx," then it will be incorrect to say that the Ratite birds have 

 no voice-organs'. As I have here shown, all these three structures are 



1 It is sometimes, though most erroneously, supposed that because a bird 

 has no intrinsic voice-muscles, it is, therefore, mute. Were such the case, all 

 the Galliufe, Ducks, Chauna, and many other noisy birds should be Toiceless. 

 As regards the Ratitw, the statement made by Meckel that they are mute or 

 nearly so {I.e. p. 571), is, I believe, equally groundless. I am assured by Mr. 

 Bartlett that all, except perhaps the Apteryx, have tbe power of making con- 

 siderable noises. As regards the Ostrich, indeed, Livingstone states that it 

 is frequently diiBcult to distinguish its bellowing from the roaring of the Lion. 



