940 



SYRINX 



YII. Most of the Osciiies seem to possess five or seven pairs of 

 syringeal muscles — no case of six pairs being known. In the 

 Corvidie they are arranged as follows: — (1) m. tracheo-bronchialis 

 ventralis, from the Trachea to the anterior ventral end of the 2nd 

 semiring ; (2) 7n. tr.-bronch. ohliqims, to the ventral end of the 3rd 

 semiring ; (3 and -t) m.. tr.-bronch. dorsalis longus et brevis, to the 

 dorsal end of the 2nd semiring, and to the inner tympaniform mem- 

 brane near the pessulus ; (5) m. syringeus ventralis, to the ventral end 

 of the 2nd semiring — shorter than and covered by No. 1 ; (6) m. 

 syr. ventri-lateralis, covered by No. 2, inserted on the membrane 

 between the 2nd and 3rd semirings ; (7) m. syr. dorsalis, to the 

 dorsal end of the 2nd semiring. 



According to the position of the sound-producing membranes, 

 three types of Syrinx are distinguishable : — Tracheal, Bronchial 

 and Tracheo-Bronchial. 



Diagram of a Tracheal and a Bronchial Syrinx. 



t.c. traelieo-clavit^ular muscle. 



I. Syrinx trachealis, in which the lower jDortion of the Trachea 

 consists of thin membranaceous walls, about six of the rings being 

 extremely thin or, as often happens, deficient. Both inner and 

 outer tympaniform membranes exist in the Bronchi as well as 

 some vibratory tracheal membranes. The few muscles, generally 

 but one pair, are Avholly lateral. The birds thus furnished are the 

 Tracheophon^, their voice is very loud, and while it is being 

 sounded the lower part of the throat swells out. They belong 

 entirely to the Neotropical Kegion, and comprising the Dendro- 

 colaptidm, Formicariidx, Pteroptochidx and Concypophagida', form a 

 tolerably well-marked group of the Passeres Clamatores. Indica- 

 tions of such a tracheophonous Syrinx exist in various Cotingidx 

 and Pittidx, as well as iji Colnmhx and Gallini^ — but the last cases 

 are clearly only analogous. 



II. Syrinx bronchialis, in which outer tympaniform membranes 

 exist between two or more successive bronchial semirings, while an 



