206 MERULID.E. 



The whole length rather less than nine inches. The 

 wings from the carpal joint to the end of the longest 

 primary, four inches and five-eighths : the first feather 

 very short ; the second rather longer than the fifth ; the 

 third and fourth nearly equal in length, longer than the 

 second ; the third the longest in the wing. 



The female is smaller than the male ; the head and upper 

 part of the neck are lighter ; the white of the breast not so 

 pure, with less of the yellow colour ; the breast spots 

 larger, and not so well defined. 



The back and scapulary feathers in young birds have 

 each a pale yellowish spot in the centre, and the smaller 

 wing-coverts streaked with pale brown. 



Varieties in colour among Thrushes are not uncommon. 



The sternum, or breastbone, in Birds may be considered 

 the most characteristic, as it is also one of the most import- 

 ant, of the bones in their skeleton. It has already been 

 observed, page 112, that the extent of surface furnished by 

 the sides and keel of this bone indicate the size and strength 

 of the muscles which move the wings, and therefore afford 

 a criterion by which to judge of the comparative power of 

 flight possessed by the species. The breastbone also sup- 

 ports and protects all the most important soft parts of the 

 body. A figure of the sternum of one species in each 

 genus, as far as practicable, will therefore be introduced 

 among the vignettes, for the purpose of illustrating generic 

 form in bone, and the general accordance in figure, in con- 

 junction with external characters and habits, may be ac- 

 cepted in proof of systematic arrangement. 



