2 CLASSIFICATION OF BIRDS. 
Order PICO-PASSERES. 
The Pico-Passeres combine three characters not known to be combined in any other 
birds :-— 
A. Young born helpless and nearly naked; not passing through a downy stage before 
acquiring feathers. B. Mlewor longus hallucis leading to one, or both, if two, hind 
toes (which is generally the hallux only, but is sometimes the fourth digit only, 
sometimes the first and fourth, and occasionally the first and second). ©, Ambiens 
and accessory femoro-caudal muscles absent. 
To this diagnosis other characters may be added :-— 
D. Spinal feather-tract well defined on the neck. EE. Cervical vertebree not exceeding 
15 in number. 






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The number of vertebre, in front of the first vertebra which is connected by a rib to the 
sternum, is not a very constant character, but is occasionally useful in diagnosis, In 
suborders 1 to 16 (with the doubtful exception of Gyps bengalensis) the number varies 
from 13 to 15. In suborders 19 to 23 and 32 to 36 the number varies from 16 to 21, 
except that in the Cygnide it reaches the extraordinary number of 23 to 25. Outside the 
Anseres the greatest variation appears to be in the Pygopodes—the Colymbidw varying 
from 14 to 15, and the Podicipide from 17 to 21. 

