188 SCANSORES. PSITTACID^E. 



Climbers, possessing yoked toes, he remarks that 

 the Parrots and the Woodpeckers are the only 

 families whose toes are strictly and constantly 

 disposed in pairs ; the external toe of the other 

 Scansores being retractile ; and these latter are 

 never seen to climb, at least to that extent which 

 is common to the two families in question. " We 

 may thus venture," he continues, " to separate the 

 Parrots and Woodpeckers from the other Families, 

 and to associate them together, in consequence of 

 the affinity in these essential characteristics of the 

 tribe. In this point of view they will compose its 

 normal groups as Climbers par excellence ; differ- 

 ing, however, as to the mode in which they climb ; 

 the Parrots using the foot chiefly in grasping the 

 object, which assists them in their ascent, and in 

 conjunction with the bill, while the Picidce rely 

 upon the strength and straightness of the hind 

 toes, in supporting them in a perpendicular posi- 

 tion on the sides of trees ; in which posture they 

 are also assisted by the strong shafts of the tail 

 feathers. While I was influenced by these gene- 

 ral points of coincidence in placing the Psittacidce 

 and Picidce together, I recognised a group which 

 appeared to intervene between them, and to di- 

 minish the apparent distance that exists even in 

 the form of their bill. That important group 

 which comprises the Linnaean Barbels,, evidently 

 exhibited the expected gradation in the structure 

 of that member ; the bill of Pogonias, ILLIG., 

 approaching most nearly that of the Parrots, by 

 its short, strong, and hooked conformation, while 

 the straighter and more lengthened bill of the 

 true Bucco united itself to that of Picus. Many- 

 other particulars in form, and also in extraordi- 



