SYRINX 



941 



inner tympaniform membrane may also be present. In typical 

 cases the Trachea has no sounding membranes, and to such belong 

 Steatornis, various CaprwmJgi and Cuculi — notably Batrachostomus, 

 Fodargus, Croto^haga, Piaya and Guira ; but there are other members 

 of these groups, as j^gotheles, Nydidromus, Cuculus and CentrojMS, 

 in addition to certain Striges, as Asio accipitrinus, which shew stages 

 intermediate between the typical Bronchial and Tracheo-bronchial 

 Syrinx, in so far as the lower part of the Trachea has incomplete 

 rings only, with no pessulus, and is, as in Centrojms, split into a right 

 and left half, so that it assumes the Bronchial character. 



III. Syrinx tracheo-bronchialis, Avhich may be regarded as the 

 normal form, the other two being modifications of it, yet it is 



B./c 



HI 



Kaven. Lateral and Dorsal View of Syrinx. 

 B.u. m. ir. second, third and fourth bronchial rings ; Nos. 1-7, as on page 940. 



difficult to give such a diagnosis of it as Avill apply to all its modi- 

 fications. The essential feature is that the proximal end of the 

 inner tympaniform membrane is attached to the last pair of tracheal 

 rings. In the Oscines the four or five distal tracheal rings are solidly 

 fused into a little box which communicates with the Bronchi ; the 

 first and second bronchial semirings are closely attached to the 

 Trachea ; and the spaces between the second and third and third 

 and fourth semirings are generally closed by outer tympaniform 

 membranes. Similar arrangements exist in many other birds ; but 

 the chief outer membrane is frequently formed between the last 

 tracheal and the first bronchial ring, as in Bhea, Anseres, S2)henisci, 

 Perdix, Cypselus, Aluco flammeus and PiUincola. Most peculiar 

 features are shewn by Gallus and the Psittaci ; but in fact the 

 modifications are very numerous, as may well be expected from the 



