PASSE-RES. 5 



The order Passeres contains about half the total number of 

 living birds, or somewhat more than 6000 species. Of these nearly 

 1000, or one sixth of the number, are found within the limits of 

 the Indian Empire, either as residents or as seasonal visitors. 



The primary division of the Passeres into two large groups is 

 based -on the mode of attachment of the muscles of the syrinx, 

 and may be thus expressed : 



Birds in which the intrinsic muscles of the syrinx 

 are fixed to the ends of the bronchial semi- 

 rings Acromyodi. 



Birds in which the intrinsic muscles of the syrinx 

 are fixed to the middle of the bronchial semi- 

 rings Mesomyodi. 



The Acromyodi have the muscles of the syrinx complex and 

 consisting of numerous pairs. The Mesomyodi have the muscles 

 simple, consisting in many cases of only one pair. 



T.i, 



Syrinx of a Magpie*, showing the Acroinyodian attachment of the intrinsic 

 muscles at the ends of the bronchial semi-rings. The left-hand figure is a side 

 view and the right-hand figure a dorsal view of the syrinx. The membranous 

 parts between the bronchial semi-rings and the internal tympaniform mem- 

 brane are dotted ; n, in are the second and third bronchial semi-rings ; T.i, the 

 internal tympaniform membrane; st, the muscle from the side of the trachea 

 to the upper end of the clavicle ; 1, 2, 3, 4, 5, 6 the syringeal muscles; there 

 is a 7th. which is hidden by the fith ; the 4th is hidden below and between 

 the 1st, 2nd, and 3rd. 



* 1 am indebted to my friend Dr. Hans Gadow for this original drawing of 

 the syrinx of a Magpie. 



